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• 1. [Article] Temperature dependence of dark current in a CCD

  We present data for dark current of a back-illuminated CCD over the temperature range of 222 to 291 K. Using an Arrhenius law, we found that the analysis of the data leads to the relation between the prefactor ...

  Citation × Citation Citation Abstract Copy Title: Temperature dependence of dark current in a CCD Author: Widenhorn, Ralf, Blouke, Morley M., Weber, Alexander, Rest, Armin, Bodegom, Erik Year: 2002 We present data for dark current of a back-illuminated CCD over the temperature range of 222 to 291 K. Using an Arrhenius law, we found that the analysis of the data leads to the relation between the prefactor and the apparent activation energy as described by the Meyer-Neldel rule. However, a more detailed analysis shows that the activation energy for the dark current changes in the temperature range investigated. This transition can be explained by the larger relative importance at high temperatures of the diffusion dark current and at low temperatures by the depletion dark current. The diffusion dark current, characterized by the band gap of silicon, is uniform for all pixels. At low temperatures, the depletion dark current, characterized by half the band gap, prevails, but it varies for different pixels. Dark current spikes are pronounced at low temperatures and can be explained by large concentrations of deep level impurities in those particular pixels. We show that fitting the data with the impurity concentration as the only variable can explain the dark current characteristics of all the pixels on the chip. Title: Temperature dependence of dark current in a CCD Author: Widenhorn, Ralf, Blouke, Morley M., Weber, Alexander, Rest, Armin, Bodegom, Erik Year: 2002 We present data for dark current of a back-illuminated CCD over the temperature range of 222 to 291 K. Using an Arrhenius law, we found that the analysis of the data leads to the relation between the prefactor and the apparent activation energy as described by the Meyer-Neldel rule. However, a more detailed analysis shows that the activation energy for the dark current changes in the temperature range investigated. This transition can be explained by the larger relative importance at high temperatures of the diffusion dark current and at low temperatures by the depletion dark current. The diffusion dark current, characterized by the band gap of silicon, is uniform for all pixels. At low temperatures, the depletion dark current, characterized by half the band gap, prevails, but it varies for different pixels. Dark current spikes are pronounced at low temperatures and can be explained by large concentrations of deep level impurities in those particular pixels. We show that fitting the data with the impurity concentration as the only variable can explain the dark current characteristics of all the pixels on the chip. Close

• 2. [Article] The Relationship Between Precipitation and Temperature Over the Contiguous United States

  The correlation between monthly total precipitation and monthly mean temperature over the 80-year period from 1905 to 1984 at nearly 1000 stations in the contiguous United States was calculated and analyzed. ...

  Citation × Citation Citation Abstract Copy Title: The Relationship Between Precipitation and Temperature Over the Contiguous United States Author: Zhao, Weining, Khalil, M. A. K. Year: 1993 The correlation between monthly total precipitation and monthly mean temperature over the 80-year period from 1905 to 1984 at nearly 1000 stations in the contiguous United States was calculated and analyzed. Both local and field significances were tested by using statistical methods. Areas of both negative and positive precipitation-temperature correlations were found. Over most of the United States, summer precipitation and temperature were negatively correlated, which indicates that warm summers tended to be dryer. This is particularly true in the central and southern Great Plains. The area south of the Great Lakes covering the eastern portion of the Corn Belt was the only major area where a significant positive correlation was found in winter. Title: The Relationship Between Precipitation and Temperature Over the Contiguous United States Author: Zhao, Weining, Khalil, M. A. K. Year: 1993 The correlation between monthly total precipitation and monthly mean temperature over the 80-year period from 1905 to 1984 at nearly 1000 stations in the contiguous United States was calculated and analyzed. Both local and field significances were tested by using statistical methods. Areas of both negative and positive precipitation-temperature correlations were found. Over most of the United States, summer precipitation and temperature were negatively correlated, which indicates that warm summers tended to be dryer. This is particularly true in the central and southern Great Plains. The area south of the Great Lakes covering the eastern portion of the Corn Belt was the only major area where a significant positive correlation was found in winter. Close

• 3. [Article] Optical properties of β″-(ET)2SF5CH2CF2SO3: A layered molecular superconductor with large discrete counterions

  We report the polarized infrared and optical reflectance of β″-(ET)₂SF₅CH₂CF₂SO₃ as a function of temperature. This fully organic superconductor displays weakly metallic behavior over the entire temperature ...

  Citation × Citation Citation Abstract Copy Title: Optical properties of β″-(ET)2SF5CH2CF2SO3: A layered molecular superconductor with large discrete counterions Author: Dong, J., Musfeldt, J. L., Schlueter, J. A., Williams, Jack M., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 1999 We report the polarized infrared and optical reflectance of β″-(ET)₂SF₅CH₂CF₂SO₃ as a function of temperature. This fully organic superconductor displays weakly metallic behavior over the entire temperature range of our investigation. The electronic properties present several unusual features including the lack of a conventional free carrier (Drude) response at low temperature, infrared localization phenomena, and an unexpected temperature dependence of the oscillator strength. Similar behavior is observed in other β and β″ superconductors above Tc, suggesting that this class of compounds is very close to a metal→insulator transition where electronic correlations are important and the Drude response carries very little spectral weight. Vibronic features increase in intensity with decreasing temperature in the infrared, as expected. The temperature dependence of key anion vibrational modes are discussed in terms of intermolecular hydrogen bonding within the anion pocket. [S0163-1829(99)04330-1] Title: Optical properties of β″-(ET)2SF5CH2CF2SO3: A layered molecular superconductor with large discrete counterions Author: Dong, J., Musfeldt, J. L., Schlueter, J. A., Williams, Jack M., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 1999 We report the polarized infrared and optical reflectance of β″-(ET)₂SF₅CH₂CF₂SO₃ as a function of temperature. This fully organic superconductor displays weakly metallic behavior over the entire temperature range of our investigation. The electronic properties present several unusual features including the lack of a conventional free carrier (Drude) response at low temperature, infrared localization phenomena, and an unexpected temperature dependence of the oscillator strength. Similar behavior is observed in other β and β″ superconductors above Tc, suggesting that this class of compounds is very close to a metal→insulator transition where electronic correlations are important and the Drude response carries very little spectral weight. Vibronic features increase in intensity with decreasing temperature in the infrared, as expected. The temperature dependence of key anion vibrational modes are discussed in terms of intermolecular hydrogen bonding within the anion pocket. [S0163-1829(99)04330-1] Close

• 4. [Article] Surface-enhanced Raman scattering at elevated temperatures

  The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by ...

  Citation × Citation Citation Abstract Copy Title: Surface-enhanced Raman scattering at elevated temperatures Author: Leung, P.T., Hider, M. H., Sánchez, Erik J. Year: 1996 The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by a spherical or spheroidal island, and the temperature effects on the surface plasmon are accounted for via a slightly modified Ujihara model. It is found that the enhancement ratio in general decreases as substrate temperature increases. For noble metals like silver, this temperature effect is particularly pronounced at scattering frequencies close to that of the surface-plasmon resonance; and for frequencies well below the surface plasmon frequency, the enhancement ratio is relatively insensitive to the change of substrate temperature. A tentative explanation is provided for our modeling results, and the implications from these results are discussed. Title: Surface-enhanced Raman scattering at elevated temperatures Author: Leung, P.T., Hider, M. H., Sánchez, Erik J. Year: 1996 The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by a spherical or spheroidal island, and the temperature effects on the surface plasmon are accounted for via a slightly modified Ujihara model. It is found that the enhancement ratio in general decreases as substrate temperature increases. For noble metals like silver, this temperature effect is particularly pronounced at scattering frequencies close to that of the surface-plasmon resonance; and for frequencies well below the surface plasmon frequency, the enhancement ratio is relatively insensitive to the change of substrate temperature. A tentative explanation is provided for our modeling results, and the implications from these results are discussed. Close

• 5. [Article] Computation of dark frames in digital imagers

  Dark current is caused by electrons that are thermally exited into the conduction band. These electrons are collected by the well of the CCD and add a false signal to the chip. We will present an algorithm ...

  Citation × Citation Citation Abstract Copy Title: Computation of dark frames in digital imagers Author: Widenhorn, Ralf, Rest, Armin, Blouke, Morley M., Berry, Richard L., Bodegom, Erik Year: 2007 Dark current is caused by electrons that are thermally exited into the conduction band. These electrons are collected by the well of the CCD and add a false signal to the chip. We will present an algorithm that automatically corrects for dark current. It uses a calibration protocol to characterize the image sensor for different temperatures. For a given exposure time, the dark current of every pixel is characteristic of a specific temperature. The dark current of every pixel can therefore be used as an indicator of the temperature. Hot pixels have the highest signal-to-noise ratio and are the best temperature sensors. We use the dark current of a several hundred hot pixels to sense the chip temperature and predict the dark current of all pixels on the chip. Dark current computation is not a new concept, but our approach is unique. Some advantages of our method include applicability for poorly temperature-controlled camera systems and the possibility of ex post facto dark current correction. Title: Computation of dark frames in digital imagers Author: Widenhorn, Ralf, Rest, Armin, Blouke, Morley M., Berry, Richard L., Bodegom, Erik Year: 2007 Dark current is caused by electrons that are thermally exited into the conduction band. These electrons are collected by the well of the CCD and add a false signal to the chip. We will present an algorithm that automatically corrects for dark current. It uses a calibration protocol to characterize the image sensor for different temperatures. For a given exposure time, the dark current of every pixel is characteristic of a specific temperature. The dark current of every pixel can therefore be used as an indicator of the temperature. Hot pixels have the highest signal-to-noise ratio and are the best temperature sensors. We use the dark current of a several hundred hot pixels to sense the chip temperature and predict the dark current of all pixels on the chip. Dark current computation is not a new concept, but our approach is unique. Some advantages of our method include applicability for poorly temperature-controlled camera systems and the possibility of ex post facto dark current correction. Close

• 6. [Article] The surface plasmon enhancement effect on adsorbed molecules at elevated temperatures

  The surface plasmon enhancement effect on adsorbed molecules at elevated substrate temperatures is studied theoretically using surface enhanced Raman scattering (SERS) as an example. The surface structure ...

  Citation × Citation Citation Abstract Copy Title: The surface plasmon enhancement effect on adsorbed molecules at elevated temperatures Author: Leung, P.T., Chiang, Hai-Pang, Tse, W. S. Year: 1998 The surface plasmon enhancement effect on adsorbed molecules at elevated substrate temperatures is studied theoretically using surface enhanced Raman scattering (SERS) as an example. The surface structure is idealized to be a monodisperse spherical particle with its nonlocal dielectric response accounted for. The temperature effects are modeled using a temperature-dependent collision frequency in the Drude model. Numerical results show that only a small decrease in the SERS enhancement ratio occurs for temperatures up to the melting point of the substrate, even for scattering close to the surface plasmon resonance frequency of the metal. More definitive results are subjected to more realistic modeling as well as systematic experimental studies. The implication of this result to other surface photochemical processes is discussed. Title: The surface plasmon enhancement effect on adsorbed molecules at elevated temperatures Author: Leung, P.T., Chiang, Hai-Pang, Tse, W. S. Year: 1998 The surface plasmon enhancement effect on adsorbed molecules at elevated substrate temperatures is studied theoretically using surface enhanced Raman scattering (SERS) as an example. The surface structure is idealized to be a monodisperse spherical particle with its nonlocal dielectric response accounted for. The temperature effects are modeled using a temperature-dependent collision frequency in the Drude model. Numerical results show that only a small decrease in the SERS enhancement ratio occurs for temperatures up to the melting point of the substrate, even for scattering close to the surface plasmon resonance frequency of the metal. More definitive results are subjected to more realistic modeling as well as systematic experimental studies. The implication of this result to other surface photochemical processes is discussed. Close

• 7. [Article] Meyer-Neldel rule for dark current in charge-coupled devices

  We present the results of a systematic study of the dark current in each pixel of a charged-coupled device chip. It was found that the Arrhenius plot, at temperatures between 222 and 291 K, deviated from ...

  Citation × Citation Citation Abstract Copy Title: Meyer-Neldel rule for dark current in charge-coupled devices Author: Widenhorn, Ralf, Mündermann, Lars, Rest, Armin, Bodegom, Erik Year: 2001 We present the results of a systematic study of the dark current in each pixel of a charged-coupled device chip. It was found that the Arrhenius plot, at temperatures between 222 and 291 K, deviated from a linear behavior in the form of continuous bending. However, as a first approximation, the dark current, D, can be expressed as: D=Dₒ exp(−ΔE/kT),where ΔE is the activation energy, k is Boltzmann’s constant, and T the absolute temperature. It was found that ΔE and the exponential prefactor Dₒ follow the Meyer–Neldel rule (MNR) for all of the more than 222,000 investigated pixels. The isokinetic temperature, Tₒ, for the process was found as 294 K. However, measurements at 313 K did not show the predicted inversion in the dark current. It was found that the dark current for different pixels merged at temperatures higher than Tₒ. A model is presented which explains the nonlinearity and the merging of the dark current for different pixels with increasing temperature. Possible implications of this finding regarding the MNR are discussed. Title: Meyer-Neldel rule for dark current in charge-coupled devices Author: Widenhorn, Ralf, Mündermann, Lars, Rest, Armin, Bodegom, Erik Year: 2001 We present the results of a systematic study of the dark current in each pixel of a charged-coupled device chip. It was found that the Arrhenius plot, at temperatures between 222 and 291 K, deviated from a linear behavior in the form of continuous bending. However, as a first approximation, the dark current, D, can be expressed as: D=Dₒ exp(−ΔE/kT),where ΔE is the activation energy, k is Boltzmann’s constant, and T the absolute temperature. It was found that ΔE and the exponential prefactor Dₒ follow the Meyer–Neldel rule (MNR) for all of the more than 222,000 investigated pixels. The isokinetic temperature, Tₒ, for the process was found as 294 K. However, measurements at 313 K did not show the predicted inversion in the dark current. It was found that the dark current for different pixels merged at temperatures higher than Tₒ. A model is presented which explains the nonlinearity and the merging of the dark current for different pixels with increasing temperature. Possible implications of this finding regarding the MNR are discussed. Close

• 8. [Article] Approximate Equations of State in Two-Temperature Plasma Mixtures

  Approximate thermodynamic state relations for multicomponent atomic and molecular gas mixtures are often constructed by artificially partitioning the mixture into its constituent materials and requiring ...

  Citation × Citation Citation Abstract Copy Title: Approximate Equations of State in Two-Temperature Plasma Mixtures Author: Ramshaw, John D., Cook, Andrew W. Year: 2014 Approximate thermodynamic state relations for multicomponent atomic and molecular gas mixtures are often constructed by artificially partitioning the mixture into its constituent materials and requiring the separated materials to be in temperature and pressure equilibrium. Iterative numerical algorithms have been employed to enforce this equilibration and compute the resulting approximate state relations in single-temperature mixtures. In partially ionized gas mixtures, there is both theoretical and empirical evidence that equilibrating the chemical potentials, number densities, or partial pressures of the free electrons is likely to produce more accurate results than equilibrating the total pressures. Moreover, in many situations of practical interest the free electrons and heavy particles have different temperatures. In this paper, we present a generalized algorithm for equilibrating the heavy-particle and electron temperaturesand a third user-specified independent thermodynamic variable in a two-temperature plasmamixture. Test calculations based on the equilibration of total pressure vs. electron pressure are presented for three different mixtures. Title: Approximate Equations of State in Two-Temperature Plasma Mixtures Author: Ramshaw, John D., Cook, Andrew W. Year: 2014 Approximate thermodynamic state relations for multicomponent atomic and molecular gas mixtures are often constructed by artificially partitioning the mixture into its constituent materials and requiring the separated materials to be in temperature and pressure equilibrium. Iterative numerical algorithms have been employed to enforce this equilibration and compute the resulting approximate state relations in single-temperature mixtures. In partially ionized gas mixtures, there is both theoretical and empirical evidence that equilibrating the chemical potentials, number densities, or partial pressures of the free electrons is likely to produce more accurate results than equilibrating the total pressures. Moreover, in many situations of practical interest the free electrons and heavy particles have different temperatures. In this paper, we present a generalized algorithm for equilibrating the heavy-particle and electron temperaturesand a third user-specified independent thermodynamic variable in a two-temperature plasmamixture. Test calculations based on the equilibration of total pressure vs. electron pressure are presented for three different mixtures. Close

• 9. [Article] Mechanisms of Methane Transport Through Trees

  Although the dynamics of methane (CH4) emission from croplands and wetlands have been fairly well investigated, the contribution of trees to global methane emission and the mechanisms of tree transport ...

  Citation × Citation Citation Abstract Copy Title: Mechanisms of Methane Transport Through Trees Author: Kutschera, Ellynne Marie Year: 2013 Although the dynamics of methane (CH4) emission from croplands and wetlands have been fairly well investigated, the contribution of trees to global methane emission and the mechanisms of tree transport are relatively unknown. Methane emissions from the common wetland tree species Populus trichocarpa (black cottonwood) native to the Pacific Northwest were measured under hydroponic conditions in order to separate plant transport mechanisms from the influence of soil processes. Roots were exposed to methane enriched water and canopy emissions of methane were measured using a canopy enclosure. Methane accumulation in the canopy was generally linear and the average canopy methane flux was 3.0 ± 2.6 μg CH4 min-1. Flux magnitudes from stem experiments scaled to the area of the main tree stem are comparable to whole-canopy flux values, indicating that the majority of methane emitted from the tree leaves through the stem. Samples for stable carbon isotope composition were taken during the canopy experiments. Compared to the isotopic composition of root water methane, canopy methane was depleted in 13C on average by 8.6 ± 3.3 permil; this indicates that methane moving through the tree is not following a purely bulk flow pathway (where no depletion would occur), but is instead subject to at least one fractionating mechanism. When temperature was varied, the flux at the coolest temperature was significantly different from the higher flux at the warmest temperature (p-value less than 0.02). The calculated Q10 for methane flux was 2.4, which indicates a positive feedback with temperature increase. Analysis of δ13C values of emitted CH4 in the temperature experiments shows increasing depletion with cooler temperatures and lower flux. This indicates that not only does the magnitude of flux vary with temperature, but the actual dominant transport mechanism changes as well. Title: Mechanisms of Methane Transport Through Trees Author: Kutschera, Ellynne Marie Year: 2013 Although the dynamics of methane (CH4) emission from croplands and wetlands have been fairly well investigated, the contribution of trees to global methane emission and the mechanisms of tree transport are relatively unknown. Methane emissions from the common wetland tree species Populus trichocarpa (black cottonwood) native to the Pacific Northwest were measured under hydroponic conditions in order to separate plant transport mechanisms from the influence of soil processes. Roots were exposed to methane enriched water and canopy emissions of methane were measured using a canopy enclosure. Methane accumulation in the canopy was generally linear and the average canopy methane flux was 3.0 ± 2.6 μg CH4 min-1. Flux magnitudes from stem experiments scaled to the area of the main tree stem are comparable to whole-canopy flux values, indicating that the majority of methane emitted from the tree leaves through the stem. Samples for stable carbon isotope composition were taken during the canopy experiments. Compared to the isotopic composition of root water methane, canopy methane was depleted in 13C on average by 8.6 ± 3.3 permil; this indicates that methane moving through the tree is not following a purely bulk flow pathway (where no depletion would occur), but is instead subject to at least one fractionating mechanism. When temperature was varied, the flux at the coolest temperature was significantly different from the higher flux at the warmest temperature (p-value less than 0.02). The calculated Q10 for methane flux was 2.4, which indicates a positive feedback with temperature increase. Analysis of δ13C values of emitted CH4 in the temperature experiments shows increasing depletion with cooler temperatures and lower flux. This indicates that not only does the magnitude of flux vary with temperature, but the actual dominant transport mechanism changes as well. Close

• 10. [Article] Temperature dependence of optical properties for amorphous silicon at wavelengths of 632.8 and 752 nm

  The temperature dependence of the optical properties for amorphous silicon is studied at wavelengths of 632.8 and 752 nm. Both the refractive index and extinction coefficient increase linearly with temperature ...

  Citation × Citation Citation Abstract Copy Title: Temperature dependence of optical properties for amorphous silicon at wavelengths of 632.8 and 752 nm Author: Leung, P.T., Do, Nhan, Yavas, Oguz, Tam, Andrew C., Leung, Wing P., Park, Hee K., Grigoropoulos, Costas P., Boneberg, Johannes, Leiderer, Paul Year: 1993 The temperature dependence of the optical properties for amorphous silicon is studied at wavelengths of 632.8 and 752 nm. Both the refractive index and extinction coefficient increase linearly with temperature for 752 nm, while the refractive index decreases and the extinction coefficient increases for 632.8 nm. The rate of increase of the extinction coefficient at 632.8 nm is twice as much as that for 752 nm. Title: Temperature dependence of optical properties for amorphous silicon at wavelengths of 632.8 and 752 nm Author: Leung, P.T., Do, Nhan, Yavas, Oguz, Tam, Andrew C., Leung, Wing P., Park, Hee K., Grigoropoulos, Costas P., Boneberg, Johannes, Leiderer, Paul Year: 1993 The temperature dependence of the optical properties for amorphous silicon is studied at wavelengths of 632.8 and 752 nm. Both the refractive index and extinction coefficient increase linearly with temperature for 752 nm, while the refractive index decreases and the extinction coefficient increases for 632.8 nm. The rate of increase of the extinction coefficient at 632.8 nm is twice as much as that for 752 nm. Close

• 11. [Article] Anomalous low-temperature and high-field magnetoresistance in the organic superconductor β″-(BEDT-TTF)2SF5CH2CF2SO3

  We report direct observations of anomalous magnetic-field and temperature dependences of the Shubnikov–de Haas oscillations in the organic superconductor β″-(BEDT-TTF)₂SF₅CH₂CF₂SO₃. Unlike other BEDT-TTF ...

  Citation × Citation Citation Abstract Copy Title: Anomalous low-temperature and high-field magnetoresistance in the organic superconductor β″-(BEDT-TTF)2SF5CH2CF2SO3 Author: Zuo, F., Su, X., Zhang, P., Brooks, J. S., Wosnitza, J., Schlueter, J. A., Williams, Jack M., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 1999 We report direct observations of anomalous magnetic-field and temperature dependences of the Shubnikov–de Haas oscillations in the organic superconductor β″-(BEDT-TTF)₂SF₅CH₂CF₂SO₃. Unlike other BEDT-TTF based organic superconductors, a nonmetallic temperature dependence of the background magnetoresistance is clearly observed. It is speculated that the nonmetallic behavior may arise from a partial nesting of the open orbits, similar to the field-induced density wave in the quasi-one-dimensional systems or a charge localization. The analysis of the magnetoresistance oscillations are found to deviate from the conventional Lifshitz-Kosevich description at high field and low temperatures. [S0163-1829(99)05433-8] Title: Anomalous low-temperature and high-field magnetoresistance in the organic superconductor β″-(BEDT-TTF)2SF5CH2CF2SO3 Author: Zuo, F., Su, X., Zhang, P., Brooks, J. S., Wosnitza, J., Schlueter, J. A., Williams, Jack M., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 1999 We report direct observations of anomalous magnetic-field and temperature dependences of the Shubnikov–de Haas oscillations in the organic superconductor β″-(BEDT-TTF)₂SF₅CH₂CF₂SO₃. Unlike other BEDT-TTF based organic superconductors, a nonmetallic temperature dependence of the background magnetoresistance is clearly observed. It is speculated that the nonmetallic behavior may arise from a partial nesting of the open orbits, similar to the field-induced density wave in the quasi-one-dimensional systems or a charge localization. The analysis of the magnetoresistance oscillations are found to deviate from the conventional Lifshitz-Kosevich description at high field and low temperatures. [S0163-1829(99)05433-8] Close

• 12. [Article] Hydrodynamic Theory of Multicomponent Diffusion and Thermal Diffusion in Multitemperature Gas Mixtures

  A phenomenological theory is developed for multicomponent diffusion, including thermal diffusion, in gas mixtures in which the components may have different temperatures. The theory is based on the hydrodynamic ...

  Citation × Citation Citation Abstract Copy Title: Hydrodynamic Theory of Multicomponent Diffusion and Thermal Diffusion in Multitemperature Gas Mixtures Author: Ramshaw, John D. Year: 1993 A phenomenological theory is developed for multicomponent diffusion, including thermal diffusion, in gas mixtures in which the components may have different temperatures. The theory is based on the hydrodynamic approach of Maxwell and Stefan, as extended and elaborated by Furry [1] and Williams [2]. The present development further extends these earlier treatments to multiple temperatures and multicomponent thermal diffusion. The resulting diffusion fluxes obey generalized Stefan-Maxwell relations which include the effects of ordinary, forced, pressure, and thermal diffusion. When thermal diffusion is neglected, these relations have the same form as the usual single-temperature ones, except that mole fractions are replaced by pressure fractions (i.e., ratios of partial pressures to total pressure). The binary and thermal diffusion coefficients are given in terms of collision integrals. Single-temperature systems and binary systems are treated as special cases of the general theory. A self-consistent effective binary diffusion approximation for multitemperature systems is presented. Title: Hydrodynamic Theory of Multicomponent Diffusion and Thermal Diffusion in Multitemperature Gas Mixtures Author: Ramshaw, John D. Year: 1993 A phenomenological theory is developed for multicomponent diffusion, including thermal diffusion, in gas mixtures in which the components may have different temperatures. The theory is based on the hydrodynamic approach of Maxwell and Stefan, as extended and elaborated by Furry [1] and Williams [2]. The present development further extends these earlier treatments to multiple temperatures and multicomponent thermal diffusion. The resulting diffusion fluxes obey generalized Stefan-Maxwell relations which include the effects of ordinary, forced, pressure, and thermal diffusion. When thermal diffusion is neglected, these relations have the same form as the usual single-temperature ones, except that mole fractions are replaced by pressure fractions (i.e., ratios of partial pressures to total pressure). The binary and thermal diffusion coefficients are given in terms of collision integrals. Single-temperature systems and binary systems are treated as special cases of the general theory. A self-consistent effective binary diffusion approximation for multitemperature systems is presented. Close

• 13. [Article] Optical, electronic, and thermodynamic properties of layered mixed anion compounds

  Mixed anion compounds that form ZrCuSiAs-type crystal structures exhibit remarkable properties such as superconductivity at low temperatures, hole conduction with optical transparency in the visible region, ...

  Citation × Citation Citation Abstract Copy Title: Optical, electronic, and thermodynamic properties of layered mixed anion compounds Author: Vielma, Jason Michael Mixed anion compounds that form ZrCuSiAs-type crystal structures exhibit remarkable properties such as superconductivity at low temperatures, hole conduction with optical transparency in the visible region, and exciton absorption at room temperature. In this thesis, properties of a selected group of materials out of the very large set of mixed anion compounds with the ZrCuSiAs-type structure are investigated by computational first principles methods. The discovery of superconductivity in LaFePO (T[subscript C] ~ 4 K) and LaFeAsO[subscript 1-x]F[subscript x] (T[subscript C] ~ 26 K) naturally led to the speculation that LaFeSbO is possibly a superconductor with an even higher transition temperature. However, all attempts to synthesize LaFeSbO failed. We performed a theoretical chemical stability analysis based on ab initio density functional theory (DFT) and determined that LaFeSbO is not stable with respect to all synthesis conditions. Instead La₂SbO₂ is found with most synthesis conditions and indeed this was found experimentally. A local stability analysis for LaFeSbO based on the calculation of the phonon dispersion curves from DFT supercells calculations reveals that LaFeSbO is potentially metastable, which opens up the possible synthesis by a non-equilibrium process. Layered oxychalcogenides LaCuChO (Ch = {S,Se,Te}) and isostructural layered fluorochalcogenides BaCuChF have drawn much interest in recent years as p-type wide bandgap semiconductors with applications in transparent electronics and photovoltaics. Previous experimental and computational studies concluded for both LaCuChO, with bandgaps between 2.4-3.1 eV, and BaCuChF, with optical bandgaps between 2.8-3.5 eV, that p-type conductivity is primarily due to copper vacancies. But, until now no quantitative defect analysis has been performed for LaCuChO. Furthermore, members of both materials show strong excitonic absorption features, which are observable at room and higher temperatures. However, disagreement exists in the literature on the origin and nature of the room temperature excitons in the respective families of materials, attributing the room temperature excitonic absorption in LaCuChO to 2 dimensional quantum confinement of hole carriers in the layered structure, and room temperature excitonic absorption in BaCuChF is described by a 3 dimensional Wannier-Mott excitonic model. A comparative ab initio computational study of the defect physics and optical properties including the excitonic effects for both families of materials has been conducted. Point defects and defect complexes are taken into account and previously omitted corrections have been included, while accurate chemical potential stability diagrams and formation energies are calculated using recently improved methods. The optical properties are calculated using the Bethe-Salpeter equation in the GW approximation. Title: Optical, electronic, and thermodynamic properties of layered mixed anion compounds Author: Vielma, Jason Michael Mixed anion compounds that form ZrCuSiAs-type crystal structures exhibit remarkable properties such as superconductivity at low temperatures, hole conduction with optical transparency in the visible region, and exciton absorption at room temperature. In this thesis, properties of a selected group of materials out of the very large set of mixed anion compounds with the ZrCuSiAs-type structure are investigated by computational first principles methods. The discovery of superconductivity in LaFePO (T[subscript C] ~ 4 K) and LaFeAsO[subscript 1-x]F[subscript x] (T[subscript C] ~ 26 K) naturally led to the speculation that LaFeSbO is possibly a superconductor with an even higher transition temperature. However, all attempts to synthesize LaFeSbO failed. We performed a theoretical chemical stability analysis based on ab initio density functional theory (DFT) and determined that LaFeSbO is not stable with respect to all synthesis conditions. Instead La₂SbO₂ is found with most synthesis conditions and indeed this was found experimentally. A local stability analysis for LaFeSbO based on the calculation of the phonon dispersion curves from DFT supercells calculations reveals that LaFeSbO is potentially metastable, which opens up the possible synthesis by a non-equilibrium process. Layered oxychalcogenides LaCuChO (Ch = {S,Se,Te}) and isostructural layered fluorochalcogenides BaCuChF have drawn much interest in recent years as p-type wide bandgap semiconductors with applications in transparent electronics and photovoltaics. Previous experimental and computational studies concluded for both LaCuChO, with bandgaps between 2.4-3.1 eV, and BaCuChF, with optical bandgaps between 2.8-3.5 eV, that p-type conductivity is primarily due to copper vacancies. But, until now no quantitative defect analysis has been performed for LaCuChO. Furthermore, members of both materials show strong excitonic absorption features, which are observable at room and higher temperatures. However, disagreement exists in the literature on the origin and nature of the room temperature excitons in the respective families of materials, attributing the room temperature excitonic absorption in LaCuChO to 2 dimensional quantum confinement of hole carriers in the layered structure, and room temperature excitonic absorption in BaCuChF is described by a 3 dimensional Wannier-Mott excitonic model. A comparative ab initio computational study of the defect physics and optical properties including the excitonic effects for both families of materials has been conducted. Point defects and defect complexes are taken into account and previously omitted corrections have been included, while accurate chemical potential stability diagrams and formation energies are calculated using recently improved methods. The optical properties are calculated using the Bethe-Salpeter equation in the GW approximation. Close

• 14. [Article] Measurements of the Mössbauer Fraction in Chromium

  Precision measurements of the Mossbauer fraction of Fe57 in chromium were made using the black absorber technique over a range of temperatures from 78K to 792K. Because of uncertainty in corrections at ...

  Citation × Citation Citation Abstract Copy Title: Measurements of the Mössbauer Fraction in Chromium Author: Brace, B. Frederick, Jr. Year: 1972 Precision measurements of the Mossbauer fraction of Fe57 in chromium were made using the black absorber technique over a range of temperatures from 78K to 792K. Because of uncertainty in corrections at high temperatures, only the data collected from 78K to 600K was used in analyzing the results. The f values were analyzed in terms of a Debye approximmation. This analysis of the data yielded a theoretical fit which was based on two adjustable parameters (a Debye temperature of 438K and an anharmonicity parameter of 2 x 10-4K-1). The f measurements were also analyzed using a theory proposed by Mannheim in 1968. Two different phonon density of states functions (Feldman, Muhlestein) were applied to Mannheim’s theory, and the resulting theoretical fits to experimental values showed a decrease in the force constant as a result of introducing an impurity into the chromium. Feldman’s phonon spectrum yielded a force constant ratio of 1.30±.07 and an anharmoncity parameter of ℇ=2.5(±.5) x 10-4K-1. Title: Measurements of the Mössbauer Fraction in Chromium Author: Brace, B. Frederick, Jr. Year: 1972 Precision measurements of the Mossbauer fraction of Fe57 in chromium were made using the black absorber technique over a range of temperatures from 78K to 792K. Because of uncertainty in corrections at high temperatures, only the data collected from 78K to 600K was used in analyzing the results. The f values were analyzed in terms of a Debye approximmation. This analysis of the data yielded a theoretical fit which was based on two adjustable parameters (a Debye temperature of 438K and an anharmonicity parameter of 2 x 10-4K-1). The f measurements were also analyzed using a theory proposed by Mannheim in 1968. Two different phonon density of states functions (Feldman, Muhlestein) were applied to Mannheim’s theory, and the resulting theoretical fits to experimental values showed a decrease in the force constant as a result of introducing an impurity into the chromium. Feldman’s phonon spectrum yielded a force constant ratio of 1.30±.07 and an anharmoncity parameter of ℇ=2.5(±.5) x 10-4K-1. Close

• 15. [Article] The Meyer-Neldel rule for diodes in forward bias

  We analyzed the temperature dependence of the forward current of a silicon diode. Instead of representing the data in the ordinarily used current versus voltage graph, the currents are plotted for different ...

  Citation × Citation Citation Abstract Copy Title: The Meyer-Neldel rule for diodes in forward bias Author: Widenhorn, Ralf, Fitzgibbons, Michael, Bodegom, Erik Year: 2004 We analyzed the temperature dependence of the forward current of a silicon diode. Instead of representing the data in the ordinarily used current versus voltage graph, the currents are plotted for different voltages as a function of the inverse temperature. The constant voltage curves can be fitted linearly and the extrapolations of the fits seem to merge to one common focal point. Hence, we demonstrate that a real diode follows the Meyer-Neldel rule (MNR). It is shown that the MNR is due to a shift of the current from ideal-diode to high-injection-diode behavior. We will argue that the merging of the different Arrhenius plots toward one focal point, and hence a MNR, can be the result of various mechanisms. The general requirements to observe a MNR are not very restrictive. It is therefore not surprising that the MNR has been observed in a multitude of systems. The origin that gives rise to the MNR can be manifold and allows for different models to explain its occurrence. Title: The Meyer-Neldel rule for diodes in forward bias Author: Widenhorn, Ralf, Fitzgibbons, Michael, Bodegom, Erik Year: 2004 We analyzed the temperature dependence of the forward current of a silicon diode. Instead of representing the data in the ordinarily used current versus voltage graph, the currents are plotted for different voltages as a function of the inverse temperature. The constant voltage curves can be fitted linearly and the extrapolations of the fits seem to merge to one common focal point. Hence, we demonstrate that a real diode follows the Meyer-Neldel rule (MNR). It is shown that the MNR is due to a shift of the current from ideal-diode to high-injection-diode behavior. We will argue that the merging of the different Arrhenius plots toward one focal point, and hence a MNR, can be the result of various mechanisms. The general requirements to observe a MNR are not very restrictive. It is therefore not surprising that the MNR has been observed in a multitude of systems. The origin that gives rise to the MNR can be manifold and allows for different models to explain its occurrence. Close

• 16. [Article] Geophysical strain and tilt : measurement methodology and analysis of data

  Tilt and strain meters were installed on the Portland State University campus in the summer of 1982 and data was collected for 4 months. Instrument selection, operation, installation and performance are ...

  Citation × Citation Citation Abstract Copy Title: Geophysical strain and tilt : measurement methodology and analysis of data Author: MacKay, Robert Year: 1983 Tilt and strain meters were installed on the Portland State University campus in the summer of 1982 and data was collected for 4 months. Instrument selection, operation, installation and performance are discussed. Suggestions that could enhance data quality and data collection efficiency are presented. An analysis procedure is suggested and an example of this procedure for an interval of data is discussed. The influence of the temperature, pressure, rainfall and solid earth tides on the signal is investigated, as well as the correlation between similar channels of the different tilt instruments. The temperature, rainfall and solid earth tides were all determined to have an influence on the instruments. A statistical test of the influence of the barometric pressure on the signal revealed no significant influence. A very low correlation between similar components of the different tilt instruments was observed aside from their thermal dependence. It was concluded that in order to obtain high quality data for the use in quantitative calculations, the temperature influence on the raw record must be minimized. Title: Geophysical strain and tilt : measurement methodology and analysis of data Author: MacKay, Robert Year: 1983 Tilt and strain meters were installed on the Portland State University campus in the summer of 1982 and data was collected for 4 months. Instrument selection, operation, installation and performance are discussed. Suggestions that could enhance data quality and data collection efficiency are presented. An analysis procedure is suggested and an example of this procedure for an interval of data is discussed. The influence of the temperature, pressure, rainfall and solid earth tides on the signal is investigated, as well as the correlation between similar channels of the different tilt instruments. The temperature, rainfall and solid earth tides were all determined to have an influence on the instruments. A statistical test of the influence of the barometric pressure on the signal revealed no significant influence. A very low correlation between similar components of the different tilt instruments was observed aside from their thermal dependence. It was concluded that in order to obtain high quality data for the use in quantitative calculations, the temperature influence on the raw record must be minimized. Close

• 17. [Article] Approximate Thermodynamic State Relations in Partially Ionized Gas Mixtures

  Thermodynamic state relations for mixtures of partially ionized nonideal gases are often approximated by artificially partitioning the mixture into compartments or subvolumes occupied by the pure partially ...

  Citation × Citation Citation Abstract Copy Title: Approximate Thermodynamic State Relations in Partially Ionized Gas Mixtures Author: Ramshaw, John D. Year: 2004 Thermodynamic state relations for mixtures of partially ionized nonideal gases are often approximated by artificially partitioning the mixture into compartments or subvolumes occupied by the pure partially ionized constituent gases, and requiring these subvolumes to be in temperature and pressure equilibrium. This intuitively reasonable procedure is easily shown to reproduce the correct thermal and caloric state equations for a mixture of neutral nonionized ideal gases. The purpose of this paper is to point out that (a) this procedure leads to incorrect state equations for a mixture of partially ionized ideal gases, whereas (b) the alternative procedure of requiring that the subvolumes all have the same temperature and free electron density reproduces the correct thermal and caloric state equations for such a mixture. These results readily generalize to the case of partially degenerate and/or relativistic electrons, to a common approximation used to represent pressure ionization effects, and to two-temperature plasmas. This suggests that equating the subvolume electron number densities or chemical potentials instead of pressures is likely to provide a more accurate approximation in nonideal plasma mixtures. Title: Approximate Thermodynamic State Relations in Partially Ionized Gas Mixtures Author: Ramshaw, John D. Year: 2004 Thermodynamic state relations for mixtures of partially ionized nonideal gases are often approximated by artificially partitioning the mixture into compartments or subvolumes occupied by the pure partially ionized constituent gases, and requiring these subvolumes to be in temperature and pressure equilibrium. This intuitively reasonable procedure is easily shown to reproduce the correct thermal and caloric state equations for a mixture of neutral nonionized ideal gases. The purpose of this paper is to point out that (a) this procedure leads to incorrect state equations for a mixture of partially ionized ideal gases, whereas (b) the alternative procedure of requiring that the subvolumes all have the same temperature and free electron density reproduces the correct thermal and caloric state equations for such a mixture. These results readily generalize to the case of partially degenerate and/or relativistic electrons, to a common approximation used to represent pressure ionization effects, and to two-temperature plasmas. This suggests that equating the subvolume electron number densities or chemical potentials instead of pressures is likely to provide a more accurate approximation in nonideal plasma mixtures. Close

• 18. [Article] Mössbauer studies of stable interstitial and substitutional sites of cobalt in gold

  Precision measurements of the Debye-Waller factor of Fe57 in Au using the wide black absorber technique have been made in the temperature range from room temperature to 830 K. The major source of error ...

  Citation × Citation Citation Abstract Copy Title: Mössbauer studies of stable interstitial and substitutional sites of cobalt in gold Author: Steen, Charles Freeland Year: 1971 Precision measurements of the Debye-Waller factor of Fe57 in Au using the wide black absorber technique have been made in the temperature range from room temperature to 830 K. The major source of error arises from Au Ly x-rays which are unresolved by the radiation detection system from the 14.4 KeV gamma ray. The K absorption edge of Br has been used to correct for the presence of x-rays. These measurements have revealed the existence of two nonequivalent lattice sites which the Co57 impurity (parent of Fe57) may occupy. One of the sites has been populated by quenching the source from temperatures greater than 1150 K and has been identified as a substitutional lattice site. From an analysis of the Mössbauer spectrum it is concluded that some of the substitutional sites may be in the vicinity of dislocations. It has been determined that the impurity-host force constant for Fe57 atoms in the substitutional site is about the same as the host-host force constant; the experimental value of the anharmonicity parameter ɛ (-2) for Fe57 in the Au is nearly the same as calculated values of ɛ (-2) for pure Au. The second site forms very slowly upon annealing the source at intermediate temperatures and has been identified as being interstitial in character. The slow rate of formation of the interstitial site indicates that diffusion is a primary mechanism in its formation. The second site must therefore be more complicated than an ordinary interstitial. It is proposed that this site is a split, or dumbbell, interstitial formed by substituting two impurity atoms for one of the Au atoms. Title: Mössbauer studies of stable interstitial and substitutional sites of cobalt in gold Author: Steen, Charles Freeland Year: 1971 Precision measurements of the Debye-Waller factor of Fe57 in Au using the wide black absorber technique have been made in the temperature range from room temperature to 830 K. The major source of error arises from Au Ly x-rays which are unresolved by the radiation detection system from the 14.4 KeV gamma ray. The K absorption edge of Br has been used to correct for the presence of x-rays. These measurements have revealed the existence of two nonequivalent lattice sites which the Co57 impurity (parent of Fe57) may occupy. One of the sites has been populated by quenching the source from temperatures greater than 1150 K and has been identified as a substitutional lattice site. From an analysis of the Mössbauer spectrum it is concluded that some of the substitutional sites may be in the vicinity of dislocations. It has been determined that the impurity-host force constant for Fe57 atoms in the substitutional site is about the same as the host-host force constant; the experimental value of the anharmonicity parameter ɛ (-2) for Fe57 in the Au is nearly the same as calculated values of ɛ (-2) for pure Au. The second site forms very slowly upon annealing the source at intermediate temperatures and has been identified as being interstitial in character. The slow rate of formation of the interstitial site indicates that diffusion is a primary mechanism in its formation. The second site must therefore be more complicated than an ordinary interstitial. It is proposed that this site is a split, or dumbbell, interstitial formed by substituting two impurity atoms for one of the Au atoms. Close

• 19. [Article] The Effect of Plasma on Graphene Quality in an Inductively Couple Plasma Chemical Vapor Deposition Reactor

  Despite continued interest in research and application development, full scale graphene production is still limited by many factors including prohibitively high growth temperature requirements. Extremely ...

  Citation × Citation Citation Abstract Copy Title: The Effect of Plasma on Graphene Quality in an Inductively Couple Plasma Chemical Vapor Deposition Reactor Author: Coyne, Brendan Year: 2017 Despite continued interest in research and application development, full scale graphene production is still limited by many factors including prohibitively high growth temperature requirements. Extremely high quality graphene growth is possible at high temperatures using chemical vapor deposition (CVD). Use of an inductively coupled plasma chemical vapor deposition (ICP CVD) reactor with the benefit of precursor gas decomposition through plasma generation, may provide possibility to reduce growth temperature. Herein, we report plasma’s effects on graphene growth by comparing growths of increasing power supplied to plasma generation and changes in precursor gas ratios. Plasma composition was characterized by ultraviolet and visible light spectroscopy; graphene was characterized by Raman spectroscopy. Plasma was observed to change gradually and in a threshold shift. Gradual changes in plasma resulted in changes in graphene quality, both defect density and number of layers. The shift produced sudden changes in graphene quality. Further, increasing power before and after the shift produced opposite correlated trends. Finally, reduced hydrogen to acetylene gas ratios produced plasma associated with higher powers at a higher gas ratio. Though the comparative plasma spectra between the two reduced gas ratio growths were very similar, the quality of graphene was different. Additionally, both lower gas ratio growths produced quality different than what was expected by the trends suggested by the higher gas ratio growths. Though plasma demonstrated a role in graphene quality, a more detailed understand of its driving mechanisms must be developed in conjunction with other growth mechanisms if it is to be utilized to substantially reduce growth temperature. Title: The Effect of Plasma on Graphene Quality in an Inductively Couple Plasma Chemical Vapor Deposition Reactor Author: Coyne, Brendan Year: 2017 Despite continued interest in research and application development, full scale graphene production is still limited by many factors including prohibitively high growth temperature requirements. Extremely high quality graphene growth is possible at high temperatures using chemical vapor deposition (CVD). Use of an inductively coupled plasma chemical vapor deposition (ICP CVD) reactor with the benefit of precursor gas decomposition through plasma generation, may provide possibility to reduce growth temperature. Herein, we report plasma’s effects on graphene growth by comparing growths of increasing power supplied to plasma generation and changes in precursor gas ratios. Plasma composition was characterized by ultraviolet and visible light spectroscopy; graphene was characterized by Raman spectroscopy. Plasma was observed to change gradually and in a threshold shift. Gradual changes in plasma resulted in changes in graphene quality, both defect density and number of layers. The shift produced sudden changes in graphene quality. Further, increasing power before and after the shift produced opposite correlated trends. Finally, reduced hydrogen to acetylene gas ratios produced plasma associated with higher powers at a higher gas ratio. Though the comparative plasma spectra between the two reduced gas ratio growths were very similar, the quality of graphene was different. Additionally, both lower gas ratio growths produced quality different than what was expected by the trends suggested by the higher gas ratio growths. Though plasma demonstrated a role in graphene quality, a more detailed understand of its driving mechanisms must be developed in conjunction with other growth mechanisms if it is to be utilized to substantially reduce growth temperature. Close

• 20. [Article] Cryogenic thin-film electron emitters

  Thin‐film electron emitters are described, which operate below 200°K and below a limiting critical applied voltage (νc) in a stable temperature‐independent regime. Current‐voltage characteristics and normal ...

  Citation × Citation Citation Abstract Copy Title: Cryogenic thin-film electron emitters Author: Smejtek, Pavel, Onn, David G., Silver, M. Year: 1974 Thin‐film electron emitters are described, which operate below 200°K and below a limiting critical applied voltage (νc) in a stable temperature‐independent regime. Current‐voltage characteristics and normal electron energy distributions are presented. Fabrication and operation criteria are outlined. Comparison with temperature‐dependent emitters is made, and possible conduction mechanisms discussed briefly. Title: Cryogenic thin-film electron emitters Author: Smejtek, Pavel, Onn, David G., Silver, M. Year: 1974 Thin‐film electron emitters are described, which operate below 200°K and below a limiting critical applied voltage (νc) in a stable temperature‐independent regime. Current‐voltage characteristics and normal electron energy distributions are presented. Fabrication and operation criteria are outlined. Comparison with temperature‐dependent emitters is made, and possible conduction mechanisms discussed briefly. Close

• 21. [Article] Multicomponent Diffusion in Two-Temperature Magnetohydrodynamics

  A recent hydrodynamic theory of multicomponent diffusion in multitemperature gas mixtures [J. D. Ramshaw, J. Non-Equilib. Thermodyn. 18, 121 (1993)] is generalized to include the velocity-dependent Lorentz ...

  Citation × Citation Citation Abstract Copy Title: Multicomponent Diffusion in Two-Temperature Magnetohydrodynamics Author: Ramshaw, John D., Chang, C. H. Year: 1996 A recent hydrodynamic theory of multicomponent diffusion in multitemperature gas mixtures [J. D. Ramshaw, J. Non-Equilib. Thermodyn. 18, 121 (1993)] is generalized to include the velocity-dependent Lorentz force on charged species in a magnetic field B. This generalization is used to extend a previous treatment of ambipolar diffusion in two-temperature multicomponent plasmas [J. D. Ramshaw and C. H. Chang, Plasma Chem. Plasma Process. 13, 489 (1993)] to situations in which B and the electrical current density are nonzero. General expressions are thereby derived for the species diffusion fluxes, including thermal diffusion, in both single- and two-temperature multicomponent magnetohydrodynamics (MHD). It is shown that the usual zerofield form of the Stefan-Maxwell equations can be preserved in the presence of B by introducing generalized binary diffusion tensors dependent on B. A self-consistent effective binary diffusion approximation is presented that provides explicit approximate expressions for the diffusion fluxes. Simplifications due to the small electron mass are exploited to obtain an ideal MHD description in which the electron diffusion coefficients drop out, resistive effects vanish, and the electric field reduces to a particularly simple form. This description should be well suited for numerical calculations. Title: Multicomponent Diffusion in Two-Temperature Magnetohydrodynamics Author: Ramshaw, John D., Chang, C. H. Year: 1996 A recent hydrodynamic theory of multicomponent diffusion in multitemperature gas mixtures [J. D. Ramshaw, J. Non-Equilib. Thermodyn. 18, 121 (1993)] is generalized to include the velocity-dependent Lorentz force on charged species in a magnetic field B. This generalization is used to extend a previous treatment of ambipolar diffusion in two-temperature multicomponent plasmas [J. D. Ramshaw and C. H. Chang, Plasma Chem. Plasma Process. 13, 489 (1993)] to situations in which B and the electrical current density are nonzero. General expressions are thereby derived for the species diffusion fluxes, including thermal diffusion, in both single- and two-temperature multicomponent magnetohydrodynamics (MHD). It is shown that the usual zerofield form of the Stefan-Maxwell equations can be preserved in the presence of B by introducing generalized binary diffusion tensors dependent on B. A self-consistent effective binary diffusion approximation is presented that provides explicit approximate expressions for the diffusion fluxes. Simplifications due to the small electron mass are exploited to obtain an ideal MHD description in which the electron diffusion coefficients drop out, resistive effects vanish, and the electric field reduces to a particularly simple form. This description should be well suited for numerical calculations. Close

• 22. [Article] Factors Affecting Methane Emissions from Rice Fields

  Methane emissions from rice fields are affected by a number of environmental and agricultural factors. We have analyzed our 7-year data set on methane emissions from rice fields in Tu Zu, China, to delineate ...

  Citation × Citation Citation Abstract Copy Title: Factors Affecting Methane Emissions from Rice Fields Author: Khalil, M. A. K., Rasmussen, R. A., Shearer, Martha J., Dalluge, R. W., Ren, Lixin, Duan, Chang-Lin Year: 1998 Methane emissions from rice fields are affected by a number of environmental and agricultural factors. We have analyzed our 7-year data set on methane emissions from rice fields in Tu Zu, China, to delineate the relationships between emissions and a number of variables that were measured at the same time. Our work was done in fields that were managed under prevailing agricultural practices of the region. Consequently, only the effect of factors that vary from year to year or during the growing season can be calculated. In our study we measured the effects of environmental variables (soil temperature, wind speed, sky cover) and agricultural factors (planting density, water level, rice cultivars, organic fertilizer amounts, yield). Of these variables, soil temperature had the most significant effect on methane emissions resulting in Q₁₀ values of about 2 (1.5–3). The effect of sky cover, and even water levels, was to change the soil temperature, which in turn affected the methane flux. Wind tended to increase emissions, possibly by agitation of the soil. Of the agricultural variables, planting density had the most significant but complex effect on methane emissions. We studied emissions from up to 4 times the normal planting density under otherwise similar agricultural conditions in the same fields. For a four fold increase in planting density the seasonal average emissions increased by about a factor of 2. Rice cultivars had a small but detectable effect. The amount of organic fertilizer and the yields did not affect methane emissions in our fields. The lack of an effect from the fertilizers is attributed to a saturation phenomenon whereby methane emissions do not respond to continual increases in organic material after some sufficiently high level. Title: Factors Affecting Methane Emissions from Rice Fields Author: Khalil, M. A. K., Rasmussen, R. A., Shearer, Martha J., Dalluge, R. W., Ren, Lixin, Duan, Chang-Lin Year: 1998 Methane emissions from rice fields are affected by a number of environmental and agricultural factors. We have analyzed our 7-year data set on methane emissions from rice fields in Tu Zu, China, to delineate the relationships between emissions and a number of variables that were measured at the same time. Our work was done in fields that were managed under prevailing agricultural practices of the region. Consequently, only the effect of factors that vary from year to year or during the growing season can be calculated. In our study we measured the effects of environmental variables (soil temperature, wind speed, sky cover) and agricultural factors (planting density, water level, rice cultivars, organic fertilizer amounts, yield). Of these variables, soil temperature had the most significant effect on methane emissions resulting in Q₁₀ values of about 2 (1.5–3). The effect of sky cover, and even water levels, was to change the soil temperature, which in turn affected the methane flux. Wind tended to increase emissions, possibly by agitation of the soil. Of the agricultural variables, planting density had the most significant but complex effect on methane emissions. We studied emissions from up to 4 times the normal planting density under otherwise similar agricultural conditions in the same fields. For a four fold increase in planting density the seasonal average emissions increased by about a factor of 2. Rice cultivars had a small but detectable effect. The amount of organic fertilizer and the yields did not affect methane emissions in our fields. The lack of an effect from the fertilizers is attributed to a saturation phenomenon whereby methane emissions do not respond to continual increases in organic material after some sufficiently high level. Close

• 23. [Article] Nanostructured Semiconductor Heterojunctions from Quantum Dot Layers

  We report the deposition of conformal thin layers of 10?50 nm thickness from II-VI quantum dot suspensions on ZnO nanowire substrates. Smooth polycrystalline films of high electronic quality can be obtained ...

  Citation × Citation Citation Abstract Copy Title: Nanostructured Semiconductor Heterojunctions from Quantum Dot Layers Author: Könenkamp, Rolf, Word, Robert Campbell, Nadarajah, Athavan Year: 2009 We report the deposition of conformal thin layers of 10?50 nm thickness from II-VI quantum dot suspensions on ZnO nanowire substrates. Smooth polycrystalline films of high electronic quality can be obtained from CdSe quantum dots after annealing at moderate temperatures. The electronic properties are adequate for detector and solar cell applications. The growth and annealing temperatures permit deposition on light-weight and flexible substrates. Some elemental diffusion of Se across the CdSe/ZnO interface occurs in the film formation. A comparison with CdS/ZnO junctions indicates that the low Se diffusion rates are essential for efficient charge transfer. Title: Nanostructured Semiconductor Heterojunctions from Quantum Dot Layers Author: Könenkamp, Rolf, Word, Robert Campbell, Nadarajah, Athavan Year: 2009 We report the deposition of conformal thin layers of 10?50 nm thickness from II-VI quantum dot suspensions on ZnO nanowire substrates. Smooth polycrystalline films of high electronic quality can be obtained from CdSe quantum dots after annealing at moderate temperatures. The electronic properties are adequate for detector and solar cell applications. The growth and annealing temperatures permit deposition on light-weight and flexible substrates. Some elemental diffusion of Se across the CdSe/ZnO interface occurs in the film formation. A comparison with CdS/ZnO junctions indicates that the low Se diffusion rates are essential for efficient charge transfer. Close

• 24. [Article] High-field magnetic resonant properties of β’–(ET)2SF5CF2SO3

  The charge transfer salt β′-(ET)₂SF₅CF₂SO₃, which has previously been considered a spin-Peierls material with a TSP;33 K, is examined using high-resolution high-field sub-millimeter/millimeter wave electron ...

  Citation × Citation Citation Abstract Copy Title: High-field magnetic resonant properties of β’–(ET)2SF5CF2SO3 Author: Gard, Gary L., Winter, Rolf Walter, Schlueter, J. A., Ward, Brian H., Jobiliong, E., Reyes, A. P., Kuhns, P., Krzystek, J., Brooks, J. S., Zvyagin, S. A., Rutel, B. Year: 2003 The charge transfer salt β′-(ET)₂SF₅CF₂SO₃, which has previously been considered a spin-Peierls material with a TSP;33 K, is examined using high-resolution high-field sub-millimeter/millimeter wave electron spin resonance (ESR), and nuclear magnetic resonance (NMR) techniques. A peak in the nuclear spin-lattice relaxation behavior in fields of 8 T, accompanied by a broadening and paramagnetic shift of the resonance line, indicates a phase transition at Tc~20 K. A pronounced change in the high-field ESR excitation spectra at ~24 T, observed at Tc~20 K, may indicate the onset of antiferromagnetic (AFM) correlations of the low temperature phase in β′-(ET)₂SF₅CF₂SO₃. Peculiarities of the low-temperature magnetic and resonance properties of β′-(ET)₂SF₅CF₂SO₃ are discussed. Title: High-field magnetic resonant properties of β’–(ET)2SF5CF2SO3 Author: Gard, Gary L., Winter, Rolf Walter, Schlueter, J. A., Ward, Brian H., Jobiliong, E., Reyes, A. P., Kuhns, P., Krzystek, J., Brooks, J. S., Zvyagin, S. A., Rutel, B. Year: 2003 The charge transfer salt β′-(ET)₂SF₅CF₂SO₃, which has previously been considered a spin-Peierls material with a TSP;33 K, is examined using high-resolution high-field sub-millimeter/millimeter wave electron spin resonance (ESR), and nuclear magnetic resonance (NMR) techniques. A peak in the nuclear spin-lattice relaxation behavior in fields of 8 T, accompanied by a broadening and paramagnetic shift of the resonance line, indicates a phase transition at Tc~20 K. A pronounced change in the high-field ESR excitation spectra at ~24 T, observed at Tc~20 K, may indicate the onset of antiferromagnetic (AFM) correlations of the low temperature phase in β′-(ET)₂SF₅CF₂SO₃. Peculiarities of the low-temperature magnetic and resonance properties of β′-(ET)₂SF₅CF₂SO₃ are discussed. Close

• 25. [Article] Dark current behavior in DSLR cameras

  Digital single-lens reflex (DSLR) cameras are examined and their dark current behavior is presented. We examine the influence of varying temperature, exposure time, and gain setting on dark current. Dark ...

  Citation × Citation Citation Abstract Copy Title: Dark current behavior in DSLR cameras Author: Dunlap, Justin Charles, Sostin, Oleg, Widenhorn, Ralf, Bodegom, Erik Year: 2009 Digital single-lens reflex (DSLR) cameras are examined and their dark current behavior is presented. We examine the influence of varying temperature, exposure time, and gain setting on dark current. Dark current behavior unique to sensors within such cameras is observed. In particular, heat is trapped within the camera body resulting in higher internal temperatures and an increase in dark current after successive images. We look at the possibility of correcting for the dark current, based on previous work done for scientific grade imagers, where hot pixels are used as indicators for the entire chip?s dark current behavior. Standard methods of dark current correction are compared to computed dark frames. Dark current is a concern for DSLR cameras as optimum conditions for limiting dark current, such as cooling the imager, are not easily obtained in the typical use of such imagers. Title: Dark current behavior in DSLR cameras Author: Dunlap, Justin Charles, Sostin, Oleg, Widenhorn, Ralf, Bodegom, Erik Year: 2009 Digital single-lens reflex (DSLR) cameras are examined and their dark current behavior is presented. We examine the influence of varying temperature, exposure time, and gain setting on dark current. Dark current behavior unique to sensors within such cameras is observed. In particular, heat is trapped within the camera body resulting in higher internal temperatures and an increase in dark current after successive images. We look at the possibility of correcting for the dark current, based on previous work done for scientific grade imagers, where hot pixels are used as indicators for the entire chip?s dark current behavior. Standard methods of dark current correction are compared to computed dark frames. Dark current is a concern for DSLR cameras as optimum conditions for limiting dark current, such as cooling the imager, are not easily obtained in the typical use of such imagers. Close

• 26. [Article] Annealing Effect on SB2S3-TiO2 Nanostructures for Solar Cell Applications

  Nanostructures composited of vertical rutile TiO₂ nanorod arrays and Sb₂S₃ nanoparticles were prepared on an F:SnO₂ conductive glass by hydrothermal method and successive ionic layer adsorption and reaction ...

  Citation × Citation Citation Abstract Copy Title: Annealing Effect on SB2S3-TiO2 Nanostructures for Solar Cell Applications Author: Li, Yitan, Wei, Lin, Zhang, Ruizi, Chen, Yanxue, Mei, Liangmo, Jiao, Jun Year: 2013 Nanostructures composited of vertical rutile TiO₂ nanorod arrays and Sb₂S₃ nanoparticles were prepared on an F:SnO₂ conductive glass by hydrothermal method and successive ionic layer adsorption and reaction method at low temperature. Sb₂S₃-sensitized TiO₂ nanorod solar cells were assembled using the SB₂S₃-TiO₂ nanostructure as the photoanode and a polysulfide solution as an electrolyte. Annealing effects on the optical and photovoltaic properties of SB₂S₃-TiO₂ nanostructure were studied systematically. As the annealing temperatures increased, a regular red shift of the bandgap of Sb₂S₃ nanoparticles was observed, where the bandgap decreased from 2.25 to 1.73 eV. At the same time, the photovoltaic conversion efficiency for the nanostructured solar cells increased from 0.46% up to 1.47% as a consequence of the annealing effect. This improvement can be explained by considering the changes in the morphology, the crystalline quality, and the optical properties caused by the annealing treatment. Title: Annealing Effect on SB2S3-TiO2 Nanostructures for Solar Cell Applications Author: Li, Yitan, Wei, Lin, Zhang, Ruizi, Chen, Yanxue, Mei, Liangmo, Jiao, Jun Year: 2013 Nanostructures composited of vertical rutile TiO₂ nanorod arrays and Sb₂S₃ nanoparticles were prepared on an F:SnO₂ conductive glass by hydrothermal method and successive ionic layer adsorption and reaction method at low temperature. Sb₂S₃-sensitized TiO₂ nanorod solar cells were assembled using the SB₂S₃-TiO₂ nanostructure as the photoanode and a polysulfide solution as an electrolyte. Annealing effects on the optical and photovoltaic properties of SB₂S₃-TiO₂ nanostructure were studied systematically. As the annealing temperatures increased, a regular red shift of the bandgap of Sb₂S₃ nanoparticles was observed, where the bandgap decreased from 2.25 to 1.73 eV. At the same time, the photovoltaic conversion efficiency for the nanostructured solar cells increased from 0.46% up to 1.47% as a consequence of the annealing effect. This improvement can be explained by considering the changes in the morphology, the crystalline quality, and the optical properties caused by the annealing treatment. Close

• 27. [Article] The Meyer-Neldel rule for a property determined by two transport mechanisms

  We propose that the Meyer-Neldel rule (MNR) arises naturally for a quantity where both an intrinsic process as well as a process involving impurities contribute. The strength of the latter depends solely ...

  Citation × Citation Citation Abstract Copy Title: The Meyer-Neldel rule for a property determined by two transport mechanisms Author: Widenhorn, Ralf, Rest, Armin, Bodegom, Erik Year: 2002 We propose that the Meyer-Neldel rule (MNR) arises naturally for a quantity where both an intrinsic process as well as a process involving impurities contribute. The strength of the latter depends solely on the density of the impurities. This leads to a spread in the apparent activation energy of the measured quantity and the observation of the MNR, even though the intrinsic processes have fixed activation energies. A consequence of the MNR is the occurrence of a temperature T[sub MN] where a measured parameter is independent of the activation energy. For the system studied, the MNR does not accurately predict the results at temperatures larger than T[sub MN]. Our model for the MNR is supported by experimental data and it also can explain the inverse MNR for low activation energies. Title: The Meyer-Neldel rule for a property determined by two transport mechanisms Author: Widenhorn, Ralf, Rest, Armin, Bodegom, Erik Year: 2002 We propose that the Meyer-Neldel rule (MNR) arises naturally for a quantity where both an intrinsic process as well as a process involving impurities contribute. The strength of the latter depends solely on the density of the impurities. This leads to a spread in the apparent activation energy of the measured quantity and the observation of the MNR, even though the intrinsic processes have fixed activation energies. A consequence of the MNR is the occurrence of a temperature T[sub MN] where a measured parameter is independent of the activation energy. For the system studied, the MNR does not accurately predict the results at temperatures larger than T[sub MN]. Our model for the MNR is supported by experimental data and it also can explain the inverse MNR for low activation energies. Close

• 28. [Article] Infrared response of charge-coupled devices

  With a band gap of silicon of 1.1eV, the largest wavelength that can excite electrons from the valence to the conduction band is roughly 1100nm. As a consequence, in, for instance, a charge-coupled device, ...

  Citation × Citation Citation Abstract Copy Title: Infrared response of charge-coupled devices Author: Loch, Matthias, Widenhorn, Ralf, Bodegom, Erik Year: 2005 With a band gap of silicon of 1.1eV, the largest wavelength that can excite electrons from the valence to the conduction band is roughly 1100nm. As a consequence, in, for instance, a charge-coupled device, the quantum efficiency (QE) for wavelengths larger than 1100nm is assumed to be zero. We found that there is a response at those longer wavelengths and that the response decreases with increasing wavelength. The QE increases with increasing chip temperature which suggests a thermally activated process. Impurities in the silicon provide the energy levels in the band gap, from which electrons can be excited either thermally or by absorption of a photon. It is these impurities that contribute to the infrared response. We characterized the response at chip temperatures of 248 K to 293 K for wavelengths from 1200 nm to 1600 nm and calculated the activation energies at these wavelengths. We found that hot pixels, i.e., pixels with extraordinary high counts in a dark frame, tend to respond stronger to infrared light than normal pixels. This correlation gets stronger for longer wavelengths. It is argued that this response can be used for probing the impurities present in the silicon bulk of the sensors Title: Infrared response of charge-coupled devices Author: Loch, Matthias, Widenhorn, Ralf, Bodegom, Erik Year: 2005 With a band gap of silicon of 1.1eV, the largest wavelength that can excite electrons from the valence to the conduction band is roughly 1100nm. As a consequence, in, for instance, a charge-coupled device, the quantum efficiency (QE) for wavelengths larger than 1100nm is assumed to be zero. We found that there is a response at those longer wavelengths and that the response decreases with increasing wavelength. The QE increases with increasing chip temperature which suggests a thermally activated process. Impurities in the silicon provide the energy levels in the band gap, from which electrons can be excited either thermally or by absorption of a photon. It is these impurities that contribute to the infrared response. We characterized the response at chip temperatures of 248 K to 293 K for wavelengths from 1200 nm to 1600 nm and calculated the activation energies at these wavelengths. We found that hot pixels, i.e., pixels with extraordinary high counts in a dark frame, tend to respond stronger to infrared light than normal pixels. This correlation gets stronger for longer wavelengths. It is argued that this response can be used for probing the impurities present in the silicon bulk of the sensors Close

• 29. [Article] Vertical Nanowire Light-Emitting Diode

  We report room-temperature, white-color electroluminescence in vertically oriented ZnO nanowires. Excitonic luminescence around 380 nm is observed as a shoulder on a broader defect-related band covering ...

  Citation × Citation Citation Abstract Copy Title: Vertical Nanowire Light-Emitting Diode Author: Könenkamp, Rolf, Word, Robert Campbell, Schlegel, C. Year: 2004 We report room-temperature, white-color electroluminescence in vertically oriented ZnO nanowires. Excitonic luminescence around 380 nm is observed as a shoulder on a broader defect-related band covering all of the visible range and centered at 620 nm. The ZnO nanowires are grown in a low-temperature process on SnO2-coated glass substrates, employing a technique that is suitable for large-area applications. The nanowires are robustly encapsulated in a thin polystyrene film deposited from high-molecular-weight solutions. Electron injection occurs through the transparent SnO2 layer, while hole injection is mediated by a p-doped polymer and an evaporated Au contact. Stable device operation is observed at ambient conditions on the time scale of 1 h. Title: Vertical Nanowire Light-Emitting Diode Author: Könenkamp, Rolf, Word, Robert Campbell, Schlegel, C. Year: 2004 We report room-temperature, white-color electroluminescence in vertically oriented ZnO nanowires. Excitonic luminescence around 380 nm is observed as a shoulder on a broader defect-related band covering all of the visible range and centered at 620 nm. The ZnO nanowires are grown in a low-temperature process on SnO2-coated glass substrates, employing a technique that is suitable for large-area applications. The nanowires are robustly encapsulated in a thin polystyrene film deposited from high-molecular-weight solutions. Electron injection occurs through the transparent SnO2 layer, while hole injection is mediated by a p-doped polymer and an evaporated Au contact. Stable device operation is observed at ambient conditions on the time scale of 1 h. Close

• 30. [Article] Structure, Dynamics, and Phase Transitions in the Fullerene Derivatives C_{60}O and C_{61}H_{2}

  The effect of perturbing the icosohedral symmetry of C60 by the addition of the side groups -O and -CH2 upon orientational order-disorder and glass transitions in solid C60 has been studied by a combination ...

  Citation × Citation Citation Abstract Copy Title: Structure, Dynamics, and Phase Transitions in the Fullerene Derivatives C_{60}O and C_{61}H_{2} Author: Meingast, C., Roth, G., Pintschovius, L., Michel, R. H., Stoermer, C., Kappes, M. M., Heiney, Paul A., Brard, Laurent, Strongin, Robert M., Smith, Amos B., III Year: 1996 The effect of perturbing the icosohedral symmetry of C60 by the addition of the side groups -O and -CH2 upon orientational order-disorder and glass transitions in solid C60 has been studied by a combination of high-resolution capacitance dilatometry and single-crystal x-ray and powder inelastic neutron scattering. Both fullerene derivatives C60O (epoxide) and C61H2 (6,5-annulene) are shown to undergo a sequence of transitions similar to that found in pure C60, i.e., a first-order orientational ordering transition just below room temperature followed by an orientational glass transition at lower temperatures. Although the exact origin of the glass transition in C61H2 is unclear, the glass transition in C60O has the same origin as that in C60, with a significantly higher degree of order due to a larger energy difference between pentagon and hexagon orientations. The dilatometric data at the glass transition indicate that, in contrast to C60, the ground-state orientation of both C60O and C61H2 molecules is that with the smallest volume, also demonstrating a significant influence of the side groups upon the details of the structure. A possible explanation of these differences in terms of steric effects is proposed. Title: Structure, Dynamics, and Phase Transitions in the Fullerene Derivatives C_{60}O and C_{61}H_{2} Author: Meingast, C., Roth, G., Pintschovius, L., Michel, R. H., Stoermer, C., Kappes, M. M., Heiney, Paul A., Brard, Laurent, Strongin, Robert M., Smith, Amos B., III Year: 1996 The effect of perturbing the icosohedral symmetry of C60 by the addition of the side groups -O and -CH2 upon orientational order-disorder and glass transitions in solid C60 has been studied by a combination of high-resolution capacitance dilatometry and single-crystal x-ray and powder inelastic neutron scattering. Both fullerene derivatives C60O (epoxide) and C61H2 (6,5-annulene) are shown to undergo a sequence of transitions similar to that found in pure C60, i.e., a first-order orientational ordering transition just below room temperature followed by an orientational glass transition at lower temperatures. Although the exact origin of the glass transition in C61H2 is unclear, the glass transition in C60O has the same origin as that in C60, with a significantly higher degree of order due to a larger energy difference between pentagon and hexagon orientations. The dilatometric data at the glass transition indicate that, in contrast to C60, the ground-state orientation of both C60O and C61H2 molecules is that with the smallest volume, also demonstrating a significant influence of the side groups upon the details of the structure. A possible explanation of these differences in terms of steric effects is proposed. Close

• 31. [Article] Effective force constant ratios : iron in iridium and rhodium

  Classical methods of analyzing heat capacity data for the characteristic moments of the frequency distribution are applied to iridium and rhodium. Impurity moments are determined from high and low temperature ...

  Citation × Citation Citation Abstract Copy Title: Effective force constant ratios : iron in iridium and rhodium Author: Munsterman, Dennis Year: 1980 Classical methods of analyzing heat capacity data for the characteristic moments of the frequency distribution are applied to iridium and rhodium. Impurity moments are determined from high and low temperature f values. These moments are combined by modern theory to estimate the magnitude of the host-host to host-impurity force constant ratio. Ratios of the various host moments are also examined. Title: Effective force constant ratios : iron in iridium and rhodium Author: Munsterman, Dennis Year: 1980 Classical methods of analyzing heat capacity data for the characteristic moments of the frequency distribution are applied to iridium and rhodium. Impurity moments are determined from high and low temperature f values. These moments are combined by modern theory to estimate the magnitude of the host-host to host-impurity force constant ratio. Ratios of the various host moments are also examined. Close

• 32. [Article] Controlled Fabrication of High-Yield CdS Nanostructures by Compartment Arrangement

  High-yield, high-purity CdS nanostructures were synthesized in a turf-like configuration using an improved vapor-liquid-solid method. To increase the yield, a compartment arrangement was employed. The ...

  Citation × Citation Citation Abstract Copy Title: Controlled Fabrication of High-Yield CdS Nanostructures by Compartment Arrangement Author: Green, Joshua M., Lawrance, Juno, Jiao, Jun Year: 2008 High-yield, high-purity CdS nanostructures were synthesized in a turf-like configuration using an improved vapor-liquid-solid method. To increase the yield, a compartment arrangement was employed. The specific kind of nanostructure fabricated was found to be directly dependent on the temperature in the compartment. Along with the high-yield growth of CdS nanorods, nanowires, and nanobelts, intertwined structures were also observed, and the electron field emission property of the intertwined structures was investigated and compared with that of other type of nanostructures. Photoluminescence measurements at 10 K showed a peak emission from the CdS nanostructures at 485 nm. Title: Controlled Fabrication of High-Yield CdS Nanostructures by Compartment Arrangement Author: Green, Joshua M., Lawrance, Juno, Jiao, Jun Year: 2008 High-yield, high-purity CdS nanostructures were synthesized in a turf-like configuration using an improved vapor-liquid-solid method. To increase the yield, a compartment arrangement was employed. The specific kind of nanostructure fabricated was found to be directly dependent on the temperature in the compartment. Along with the high-yield growth of CdS nanorods, nanowires, and nanobelts, intertwined structures were also observed, and the electron field emission property of the intertwined structures was investigated and compared with that of other type of nanostructures. Photoluminescence measurements at 10 K showed a peak emission from the CdS nanostructures at 485 nm. Close

• 33. [Article] Remote Plasma Assisted Growth of Graphene Films

  Single and multiple layers of graphene films were grown on 111 oriented single crystals of nickel and polycrystalline nickel films using remote plasma assisted chemical vapor deposition. Remote plasma ...

  Citation × Citation Citation Abstract Copy Title: Remote Plasma Assisted Growth of Graphene Films Author: Nandamuri, Gopichand, Roumimov, Sergei, Solanki, Raj Year: 2010 Single and multiple layers of graphene films were grown on 111 oriented single crystals of nickel and polycrystalline nickel films using remote plasma assisted chemical vapor deposition. Remote plasma was employed to eliminate the effect of the plasma electrical field on the orientation of the grown graphene films, as well as to reduce the growth temperature compared to conventional chemical vapor deposition. The electrical and optical properties, including high resolution transmission electron microscopy of these films, suggest that this approach is both versatile and scalable for potential large area optoelectronic applications. Title: Remote Plasma Assisted Growth of Graphene Films Author: Nandamuri, Gopichand, Roumimov, Sergei, Solanki, Raj Year: 2010 Single and multiple layers of graphene films were grown on 111 oriented single crystals of nickel and polycrystalline nickel films using remote plasma assisted chemical vapor deposition. Remote plasma was employed to eliminate the effect of the plasma electrical field on the orientation of the grown graphene films, as well as to reduce the growth temperature compared to conventional chemical vapor deposition. The electrical and optical properties, including high resolution transmission electron microscopy of these films, suggest that this approach is both versatile and scalable for potential large area optoelectronic applications. Close

• 34. [Article] Anisotropic magnetoresistance in the organic superconductor β″–(BEDT-TTF)2SF5CH2CF2SO3

  In this paper, we report transport measurements of interlayer magnetoresistance with field parallel and perpendicular to the current direction in an all organic superconductor β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃. ...

  Citation × Citation Citation Abstract Copy Title: Anisotropic magnetoresistance in the organic superconductor β″–(BEDT-TTF)2SF5CH2CF2SO3 Author: Su, X., Zuo, F., Schlueter, J. A., Williams, Jack M., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 1999 In this paper, we report transport measurements of interlayer magnetoresistance with field parallel and perpendicular to the current direction in an all organic superconductor β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃. For H∥I, the isothermal magnetoresistance R(H) at low temperatures (T Title: Anisotropic magnetoresistance in the organic superconductor β″–(BEDT-TTF)2SF5CH2CF2SO3 Author: Su, X., Zuo, F., Schlueter, J. A., Williams, Jack M., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 1999 In this paper, we report transport measurements of interlayer magnetoresistance with field parallel and perpendicular to the current direction in an all organic superconductor β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃. For H∥I, the isothermal magnetoresistance R(H) at low temperatures (T Close

• 35. [Article] Transmission studies of explosive vaporization of a transparent liquid film on an opaque solid surface induced by excimer-laser-pulsed irradiation

  Examines the dynamics of the explosion of a liquid film by an ultraviolet excimer pulsed laser studied experimentally on top of an amorphous silicon film deposited on fused quartz. Background on thermal ...

  Citation × Citation Citation Abstract Copy Title: Transmission studies of explosive vaporization of a transparent liquid film on an opaque solid surface induced by excimer-laser-pulsed irradiation Author: Leung, P.T., Do, Nhan, Klees, Leander, Leung, Wing P., Tong, Frank Year: 1992 Examines the dynamics of the explosion of a liquid film by an ultraviolet excimer pulsed laser studied experimentally on top of an amorphous silicon film deposited on fused quartz. Background on thermal physics of superheated pure or mixed liquids; Techniques for surface temperature measurement; Experimental of probe laser and pulsed excimer laser. Title: Transmission studies of explosive vaporization of a transparent liquid film on an opaque solid surface induced by excimer-laser-pulsed irradiation Author: Leung, P.T., Do, Nhan, Klees, Leander, Leung, Wing P., Tong, Frank Year: 1992 Examines the dynamics of the explosion of a liquid film by an ultraviolet excimer pulsed laser studied experimentally on top of an amorphous silicon film deposited on fused quartz. Background on thermal physics of superheated pure or mixed liquids; Techniques for surface temperature measurement; Experimental of probe laser and pulsed excimer laser. Close

• 36. [Article] Residual images in charged-coupled device detectors

  We present results of a systematic study of persistent, or residual, images that occur in charged-coupled device (CCD) detectors. A phenomenological model for these residual images, also known as "ghosting," ...

  Citation × Citation Citation Abstract Copy Title: Residual images in charged-coupled device detectors Author: Rest, Armin, Mündermann, Lars, Widenhorn, Ralf, Bodegom, Erik, McGlinn, T. C. Year: 2002 We present results of a systematic study of persistent, or residual, images that occur in charged-coupled device (CCD) detectors. A phenomenological model for these residual images, also known as "ghosting," is introduced. This model relates the excess dark current in a CCD after exposure to the number of filled impurity sites which is tested for various temperatures and exposure times. We experimentally derive values for the cross section, density, and characteristic energy of the impurity sites responsible for the residual images. Title: Residual images in charged-coupled device detectors Author: Rest, Armin, Mündermann, Lars, Widenhorn, Ralf, Bodegom, Erik, McGlinn, T. C. Year: 2002 We present results of a systematic study of persistent, or residual, images that occur in charged-coupled device (CCD) detectors. A phenomenological model for these residual images, also known as "ghosting," is introduced. This model relates the excess dark current in a CCD after exposure to the number of filled impurity sites which is tested for various temperatures and exposure times. We experimentally derive values for the cross section, density, and characteristic energy of the impurity sites responsible for the residual images. Close

• 37. [Article] On the Production of the Positive Antihydrogen Ion H̄+ via Radiative Attachment

  We provide an estimate of the cross section for the radiative attachment of a second positron into the state of the ion using Ohmura and Ohmura's (1960 Phys. Rev. 118 154) effective range theory and the ...

  Citation × Citation Citation Abstract Copy Title: On the Production of the Positive Antihydrogen Ion H̄+ via Radiative Attachment Author: Keating, Chris M., Charlton, M., Straton, Jack C. Year: 2014 We provide an estimate of the cross section for the radiative attachment of a second positron into the state of the ion using Ohmura and Ohmura's (1960 Phys. Rev. 118 154) effective range theory and the principle of detailed balance. The ion can potentially be created using interactions of positrons with trapped antihydrogen, and our analysis includes a discussion in which estimates of production rates are given. Motivations to produce include its potential use as an intermediary to cool antihydrogen to ultra-cold (sub-mK) temperatures for a variety of studies, including spectroscopy and probing the gravitational interaction of the anti-atom. Title: On the Production of the Positive Antihydrogen Ion H̄+ via Radiative Attachment Author: Keating, Chris M., Charlton, M., Straton, Jack C. Year: 2014 We provide an estimate of the cross section for the radiative attachment of a second positron into the state of the ion using Ohmura and Ohmura's (1960 Phys. Rev. 118 154) effective range theory and the principle of detailed balance. The ion can potentially be created using interactions of positrons with trapped antihydrogen, and our analysis includes a discussion in which estimates of production rates are given. Motivations to produce include its potential use as an intermediary to cool antihydrogen to ultra-cold (sub-mK) temperatures for a variety of studies, including spectroscopy and probing the gravitational interaction of the anti-atom. Close

• 38. [Article] Study of the numerical modeling of the temperature dependence of the dark current in Charge Coupled Devices

  As it is well known, the classical works of the Dark Current Spectroscopy method allow - using some not too accurate theoretical relations, but huge numbers of dark current values for thousands of pixels ...

  Citation × Citation Citation Abstract Copy Title: Study of the numerical modeling of the temperature dependence of the dark current in Charge Coupled Devices Author: Widenhorn, Ralf, Tunaru, Ionel, Bodegom, Erik, Iordache, Dan A. Year: 2010 As it is well known, the classical works of the Dark Current Spectroscopy method allow - using some not too accurate theoretical relations, but huge numbers of dark current values for thousands of pixels - the evaluation of a reduced number of basic impurities parameters. Unlike these works, this paper tries to obtain--by means of some better approximations of the Shockley-Read-Hall (SRH) model--more information about the studied impurities, as well as the study of the compatibility of the used theoretical model SRH relative to the experimental data. In this manner, both the compatibility SRH model with the studied experimental data was checked up, as well as the values of some additional physical parameters of the impurified semiconductor (the logarithms of the pre-exponential factors lnDiff, lnDep, the effective value of the energy gap Eg) and of the separate capture cross-sections of the free electrons, and holes, respectively, by the studied deep-level contaminants, were evaluated. Title: Study of the numerical modeling of the temperature dependence of the dark current in Charge Coupled Devices Author: Widenhorn, Ralf, Tunaru, Ionel, Bodegom, Erik, Iordache, Dan A. Year: 2010 As it is well known, the classical works of the Dark Current Spectroscopy method allow - using some not too accurate theoretical relations, but huge numbers of dark current values for thousands of pixels - the evaluation of a reduced number of basic impurities parameters. Unlike these works, this paper tries to obtain--by means of some better approximations of the Shockley-Read-Hall (SRH) model--more information about the studied impurities, as well as the study of the compatibility of the used theoretical model SRH relative to the experimental data. In this manner, both the compatibility SRH model with the studied experimental data was checked up, as well as the values of some additional physical parameters of the impurified semiconductor (the logarithms of the pre-exponential factors lnDiff, lnDep, the effective value of the energy gap Eg) and of the separate capture cross-sections of the free electrons, and holes, respectively, by the studied deep-level contaminants, were evaluated. Close

• 39. [Article] Interpreting Activation Energies in Digital Image Sensors

  We present a study demonstrating the dependence of apparent activation energies on signal charge in digital image sensors. The data presented in this paper are for a charge-coupled device imager, but the ...

  Citation × Citation Citation Abstract Copy Title: Interpreting Activation Energies in Digital Image Sensors Author: Dunlap, Justin C., Blouke, Morley M., Bodegom, Erik, Widenhorn, Ralf Year: 2015 We present a study demonstrating the dependence of apparent activation energies on signal charge in digital image sensors. The data presented in this paper are for a charge-coupled device imager, but the analysis can be applied to CMOS sensors or generally to any system that shows nonlinearity with respect to time. Activation energies for some pixels are observed to vary between values at about half the bandgap of silicon, when calculated at low signal-charge levels, to values approaching the bandgap when calculated at high signal-charge levels. As such, the traditional method of calculating activation energies using a single exposure time at varying temperatures will result in different activation energies dependent on the exposure time chosen, making it difficult to draw physically meaningful conclusions from its value. Therefore, a method of calculating activation energies using a single signal-charge level is proposed, making it easier to correlate activation energies with impurities. Further, we demonstrate how a model of a pixel with a fixed location impurity in conjunction with a moving depletion edge, due to a changing depletion region size, can lead to this behavior. Title: Interpreting Activation Energies in Digital Image Sensors Author: Dunlap, Justin C., Blouke, Morley M., Bodegom, Erik, Widenhorn, Ralf Year: 2015 We present a study demonstrating the dependence of apparent activation energies on signal charge in digital image sensors. The data presented in this paper are for a charge-coupled device imager, but the analysis can be applied to CMOS sensors or generally to any system that shows nonlinearity with respect to time. Activation energies for some pixels are observed to vary between values at about half the bandgap of silicon, when calculated at low signal-charge levels, to values approaching the bandgap when calculated at high signal-charge levels. As such, the traditional method of calculating activation energies using a single exposure time at varying temperatures will result in different activation energies dependent on the exposure time chosen, making it difficult to draw physically meaningful conclusions from its value. Therefore, a method of calculating activation energies using a single signal-charge level is proposed, making it easier to correlate activation energies with impurities. Further, we demonstrate how a model of a pixel with a fixed location impurity in conjunction with a moving depletion edge, due to a changing depletion region size, can lead to this behavior. Close

• 40. [Article] Laser as a Tool to Study Radiation Effects in CMOS

  Energetic particles from cosmic ray or terrestrial sources can strike sensitive areas of CMOS devices and cause soft errors. Understanding the effects of such interactions is crucial as the device technology ...

  Citation × Citation Citation Abstract Copy Title: Laser as a Tool to Study Radiation Effects in CMOS Author: Ajdari, Bahar Year: 2017 Energetic particles from cosmic ray or terrestrial sources can strike sensitive areas of CMOS devices and cause soft errors. Understanding the effects of such interactions is crucial as the device technology advances, and chip reliability has become more important than ever. Particle accelerator testing has been the standard method to characterize the sensitivity of chips to single event upsets (SEUs). However, because of their costs and availability limitations, other techniques have been explored. Pulsed laser has been a successful tool for characterization of SEU behavior, but to this day, laser has not been recognized as a comparable method to beam testing. In this thesis, I propose a methodology of correlating laser soft error rate (SER) to particle beam gathered data. Additionally, results are presented showing a temperature dependence of SER and the "neighbor effect" phenomenon where due to the close proximity of devices a "weakening effect" in the ON state can be observed. Title: Laser as a Tool to Study Radiation Effects in CMOS Author: Ajdari, Bahar Year: 2017 Energetic particles from cosmic ray or terrestrial sources can strike sensitive areas of CMOS devices and cause soft errors. Understanding the effects of such interactions is crucial as the device technology advances, and chip reliability has become more important than ever. Particle accelerator testing has been the standard method to characterize the sensitivity of chips to single event upsets (SEUs). However, because of their costs and availability limitations, other techniques have been explored. Pulsed laser has been a successful tool for characterization of SEU behavior, but to this day, laser has not been recognized as a comparable method to beam testing. In this thesis, I propose a methodology of correlating laser soft error rate (SER) to particle beam gathered data. Additionally, results are presented showing a temperature dependence of SER and the "neighbor effect" phenomenon where due to the close proximity of devices a "weakening effect" in the ON state can be observed. Close

• 41. [Article] Existence of High-Order Superlattices in Orientationally Ordered C_{60}

  We correlate the presence or absence of high-order modulated structures in solid C60 with the differential scanning calorimetry signature of the orientational ordering transition and other diagnostic data. ...

  Citation × Citation Citation Abstract Copy Title: Existence of High-Order Superlattices in Orientationally Ordered C_{60} Author: Fischer, J. E., Luzzi, D. E., Kniaź, K., McGhie, A. R., Ricketts-Foot, D. A., Romanow, W. R., Vaughan, Gavin B. M., Li, Dayin, Smith, Allan L., Strongin, Robert M., Cichy, M. A., Bard, Laurent, Smith, Amos B., III Year: 1993 We correlate the presence or absence of high-order modulated structures in solid C60 with the differential scanning calorimetry signature of the orientational ordering transition and other diagnostic data. We have searched for, but not observed, the 2a face-centered cubic structure recently observed in low-temperature electron and single-crystal x-ray diffraction. We conclude that the intrinsic ground state is the previously reported simple cubic structure [space groupPa3¯, a(14 K)=14.06 Å], and that other structures may be stabilized by defects or impurities. Title: Existence of High-Order Superlattices in Orientationally Ordered C_{60} Author: Fischer, J. E., Luzzi, D. E., Kniaź, K., McGhie, A. R., Ricketts-Foot, D. A., Romanow, W. R., Vaughan, Gavin B. M., Li, Dayin, Smith, Allan L., Strongin, Robert M., Cichy, M. A., Bard, Laurent, Smith, Amos B., III Year: 1993 We correlate the presence or absence of high-order modulated structures in solid C60 with the differential scanning calorimetry signature of the orientational ordering transition and other diagnostic data. We have searched for, but not observed, the 2a face-centered cubic structure recently observed in low-temperature electron and single-crystal x-ray diffraction. We conclude that the intrinsic ground state is the previously reported simple cubic structure [space groupPa3¯, a(14 K)=14.06 Å], and that other structures may be stabilized by defects or impurities. Close

• 42. [Article] Unusual Thermal Stability of a Site-Ordered MC60 Rocksalt Structure (M=K, Rb, or Cs).

  X-ray diffraction and differential scanning calorimetry of MxC60, with x∼1 and M=K, Rb, or Cs, reveal an unusual T-dependent phase sequence. A low-symmetry ground state is found, while the high-T limit ...

  Citation × Citation Citation Abstract Copy Title: Unusual Thermal Stability of a Site-Ordered MC60 Rocksalt Structure (M=K, Rb, or Cs). Author: Zhu, Q., Zhou, O., Fischer, J. E., McGhie, Andrew R., Romanow, W. R., Strongin, Robert M., Cichy, M. A., Smith, Amos B., III Year: 1993 X-ray diffraction and differential scanning calorimetry of MxC60, with x∼1 and M=K, Rb, or Cs, reveal an unusual T-dependent phase sequence. A low-symmetry ground state is found, while the high-T limit is an ordered rocksalt structure in which only the octahedral sites are occupied. The unusual high-T stability of this ordered phase is attributed to the entropy of molecular orientational disorder and/or thermal disorder of the alkali-metal ions within the octahedral sites. Unique to KxC60 with x≥1.4, we find at intermediate temperatures an fcc site-disordered lattice gas phase with random occupancy of tetrahedral and octahedral sites, which is thus isostructural with superconducting K3C60. Title: Unusual Thermal Stability of a Site-Ordered MC60 Rocksalt Structure (M=K, Rb, or Cs). Author: Zhu, Q., Zhou, O., Fischer, J. E., McGhie, Andrew R., Romanow, W. R., Strongin, Robert M., Cichy, M. A., Smith, Amos B., III Year: 1993 X-ray diffraction and differential scanning calorimetry of MxC60, with x∼1 and M=K, Rb, or Cs, reveal an unusual T-dependent phase sequence. A low-symmetry ground state is found, while the high-T limit is an ordered rocksalt structure in which only the octahedral sites are occupied. The unusual high-T stability of this ordered phase is attributed to the entropy of molecular orientational disorder and/or thermal disorder of the alkali-metal ions within the octahedral sites. Unique to KxC60 with x≥1.4, we find at intermediate temperatures an fcc site-disordered lattice gas phase with random occupancy of tetrahedral and octahedral sites, which is thus isostructural with superconducting K3C60. Close

• 43. [Article] Structure and Phase Transition of the 6,5-Annulene Isomer of C_{61}H_{2}

  We have used differential scanning calorimetry and x-ray diffraction to study the crystalline phases of the 6,5-annulene isomer of C61H2. At 308 K the methylenated fullerenes are orientationally disordered ...

  Citation × Citation Citation Abstract Copy Title: Structure and Phase Transition of the 6,5-Annulene Isomer of C_{61}H_{2} Author: Lommen, Andrea N., Heiney, Paul A., Vaughan, Gavin B. M., Stephens, Peter W., Liu, Dengfa, Li, Dayin, Smith, Allan L., McGhie, Andrew R., Strongin, Robert M., Brard, Laurent, Smith, Amos B., III Year: 1994 We have used differential scanning calorimetry and x-ray diffraction to study the crystalline phases of the 6,5-annulene isomer of C61H2. At 308 K the methylenated fullerenes are orientationally disordered in a face-centered cubic lattice with lattice parameter 14.19±0.02 Å. Below Tc=290 K the symmetry is lowered to Pa3¯, a simple-cubic structure. At 20 K the lattice parameter is 14.06±0.02 Å, with substantial statistical disorder remaining. The transition temperature in C61H2 is slightly higher than in C60O and higher still than in C60, but the three compounds exhibit orientationally ordering transitions between qualitatively similar phases. Title: Structure and Phase Transition of the 6,5-Annulene Isomer of C_{61}H_{2} Author: Lommen, Andrea N., Heiney, Paul A., Vaughan, Gavin B. M., Stephens, Peter W., Liu, Dengfa, Li, Dayin, Smith, Allan L., McGhie, Andrew R., Strongin, Robert M., Brard, Laurent, Smith, Amos B., III Year: 1994 We have used differential scanning calorimetry and x-ray diffraction to study the crystalline phases of the 6,5-annulene isomer of C61H2. At 308 K the methylenated fullerenes are orientationally disordered in a face-centered cubic lattice with lattice parameter 14.19±0.02 Å. Below Tc=290 K the symmetry is lowered to Pa3¯, a simple-cubic structure. At 20 K the lattice parameter is 14.06±0.02 Å, with substantial statistical disorder remaining. The transition temperature in C61H2 is slightly higher than in C60O and higher still than in C60, but the three compounds exhibit orientationally ordering transitions between qualitatively similar phases. Close

• 44. [Article] Coherence Peak and Superconducting Energy Gap in Rb_{3}C_{60} Observed by Muon Spin Relaxation

  Muon spin relaxation resulting from spin exchange scattering of endohedral muonium (μ+e-) with thermal electronic excitations has been observed in the fullerene superconductor Rb3C60. The temperature dependence ...

  Citation × Citation Citation Abstract Copy Title: Coherence Peak and Superconducting Energy Gap in Rb_{3}C_{60} Observed by Muon Spin Relaxation Author: Kiefl, R. F., MacFarlane, W. A., Chow, K. H., Dunsiger, S., Duty, T. L., Johnston, T. M. S., Schneider, J. W., Sonier, J., Brard, Laurent, Strongin, Robert M., Fischer, J. E., Smith, Amos B., III Year: 1993 Muon spin relaxation resulting from spin exchange scattering of endohedral muonium (μ+e-) with thermal electronic excitations has been observed in the fullerene superconductor Rb3C60. The temperature dependence of T1-1 shows a coherence peak just below Tc and can be fit to the conventional Hebel-Slichter theory for spin relaxation in a superconductor with a broadened BCS density of states. The average energy gap for electronic excitations, Δ/kB=53(4) K or 2Δ/ kBTc=3.6(3), is consistent with the BCS weak coupling limit. Title: Coherence Peak and Superconducting Energy Gap in Rb_{3}C_{60} Observed by Muon Spin Relaxation Author: Kiefl, R. F., MacFarlane, W. A., Chow, K. H., Dunsiger, S., Duty, T. L., Johnston, T. M. S., Schneider, J. W., Sonier, J., Brard, Laurent, Strongin, Robert M., Fischer, J. E., Smith, Amos B., III Year: 1993 Muon spin relaxation resulting from spin exchange scattering of endohedral muonium (μ+e-) with thermal electronic excitations has been observed in the fullerene superconductor Rb3C60. The temperature dependence of T1-1 shows a coherence peak just below Tc and can be fit to the conventional Hebel-Slichter theory for spin relaxation in a superconductor with a broadened BCS density of states. The average energy gap for electronic excitations, Δ/kB=53(4) K or 2Δ/ kBTc=3.6(3), is consistent with the BCS weak coupling limit. Close

• 45. [Article] Influence of Illumination on Dark Current in Charge-Coupled Device Imagers

  Thermal excitation of electrons is a major source of noise in charge-coupled-device (CCD) imagers. Those electrons are generated even in the absence of light, hence, the name dark current. Dark current ...

  Citation × Citation Citation Abstract Copy Title: Influence of Illumination on Dark Current in Charge-Coupled Device Imagers Author: Widenhorn, Ralf, Hartwig, Ines, Dunlap, Justin Charles, Bodegom, Erik Year: 2009 Thermal excitation of electrons is a major source of noise in charge-coupled-device (CCD) imagers. Those electrons are generated even in the absence of light, hence, the name dark current. Dark current is particularly important for long exposure times and elevated temperatures. The standard procedure to correct for dark current is to take several pictures under the same condition as the real image, except with the shutter closed. The resulting dark frame is later subtracted from the exposed image. We address the question of whether the dark current produced in an image taken with a closed shutter is identical to the dark current produced in an exposure in the presence of light. In our investigation, we illuminated two different CCD chips with different intensities of light and measured the dark current generation. A surprising result of this study is that some pixels produce a different amount of dark current under illumination. Finally, we discuss the implication of this finding for dark frame image correction. Title: Influence of Illumination on Dark Current in Charge-Coupled Device Imagers Author: Widenhorn, Ralf, Hartwig, Ines, Dunlap, Justin Charles, Bodegom, Erik Year: 2009 Thermal excitation of electrons is a major source of noise in charge-coupled-device (CCD) imagers. Those electrons are generated even in the absence of light, hence, the name dark current. Dark current is particularly important for long exposure times and elevated temperatures. The standard procedure to correct for dark current is to take several pictures under the same condition as the real image, except with the shutter closed. The resulting dark frame is later subtracted from the exposed image. We address the question of whether the dark current produced in an image taken with a closed shutter is identical to the dark current produced in an exposure in the presence of light. In our investigation, we illuminated two different CCD chips with different intensities of light and measured the dark current generation. A surprising result of this study is that some pixels produce a different amount of dark current under illumination. Finally, we discuss the implication of this finding for dark frame image correction. Close

• 46. [Article] Specific heat and critical fields of the organic superconductor β″–(BEDT-TTF)2SF5CH2CF2SO3

  We report on specific-heat, magnetization, and ac-susceptibility measurements of β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃, an organic superconductor with Tc=4.5 K, where BEDT-TTF stands for bis(ethylenedithio)-tetrathiafulvalene. ...

  Citation × Citation Citation Abstract Copy Title: Specific heat and critical fields of the organic superconductor β″–(BEDT-TTF)2SF5CH2CF2SO3 Author: Wanka, S., Hagel, J., Beckmanm, D., Wosnitza, J., Schlueter, J. A., Williams, Jack M., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 1998 We report on specific-heat, magnetization, and ac-susceptibility measurements of β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃, an organic superconductor with Tc=4.5 K, where BEDT-TTF stands for bis(ethylenedithio)-tetrathiafulvalene. The jump of the specific heat C at Tc and the exact form of the specific heat difference between C in the superconducting (B=0 T) and in the normal (B=3.5 T) state can be well described by BCS theory with strong coupling. We estimate an electron-phonon coupling parameter λ≈1.1. From measurements of C in magnetic fields we extract the upper critical field Bc₂(T). Low-field dc-magnetization measurements were used to determine the temperature dependence of the lower critical field Bc₁. From Tc down to ~3 K the characteristic suppression of Bc1(T) below the sensitivity limit is observed. Title: Specific heat and critical fields of the organic superconductor β″–(BEDT-TTF)2SF5CH2CF2SO3 Author: Wanka, S., Hagel, J., Beckmanm, D., Wosnitza, J., Schlueter, J. A., Williams, Jack M., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 1998 We report on specific-heat, magnetization, and ac-susceptibility measurements of β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃, an organic superconductor with Tc=4.5 K, where BEDT-TTF stands for bis(ethylenedithio)-tetrathiafulvalene. The jump of the specific heat C at Tc and the exact form of the specific heat difference between C in the superconducting (B=0 T) and in the normal (B=3.5 T) state can be well described by BCS theory with strong coupling. We estimate an electron-phonon coupling parameter λ≈1.1. From measurements of C in magnetic fields we extract the upper critical field Bc₂(T). Low-field dc-magnetization measurements were used to determine the temperature dependence of the lower critical field Bc₁. From Tc down to ~3 K the characteristic suppression of Bc1(T) below the sensitivity limit is observed. Close

• 47. [Article] Shubnikov–de Haas effect in the superconducting state of an organic superconductor

  We report the observation of Shubnikov–de Haas (SdH) oscillations in the mixed state of the organic superconductor β″-(BEDT-TTF)₂SF₅CH₂CF₂SO₃ (Tc≈4.4K). At low temperatures the SdH oscillations persist ...

  Citation × Citation Citation Abstract Copy Title: Shubnikov–de Haas effect in the superconducting state of an organic superconductor Author: Wosnitza, J., Wanka, S., Hagel, J., Häussler, R., Löhneysen, H. v., Schlueter, J. A., Geiser, U., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 2000 We report the observation of Shubnikov–de Haas (SdH) oscillations in the mixed state of the organic superconductor β″-(BEDT-TTF)₂SF₅CH₂CF₂SO₃ (Tc≈4.4K). At low temperatures the SdH oscillations persist clearly below the upper critical field Bc₂(0)≈3.6 T almost down to the field where the resistivity vanishes. Rather unusually, no additional damping of the SdH-signal amplitude — as well as of the de Haas–van Alphen amplitude — is observed in the superconducting state. This indicates that the damping in the vortex state of this quasi-two-dimensional superconductor is different in character to that observed for most three-dimensional materials. Title: Shubnikov–de Haas effect in the superconducting state of an organic superconductor Author: Wosnitza, J., Wanka, S., Hagel, J., Häussler, R., Löhneysen, H. v., Schlueter, J. A., Geiser, U., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 2000 We report the observation of Shubnikov–de Haas (SdH) oscillations in the mixed state of the organic superconductor β″-(BEDT-TTF)₂SF₅CH₂CF₂SO₃ (Tc≈4.4K). At low temperatures the SdH oscillations persist clearly below the upper critical field Bc₂(0)≈3.6 T almost down to the field where the resistivity vanishes. Rather unusually, no additional damping of the SdH-signal amplitude — as well as of the de Haas–van Alphen amplitude — is observed in the superconducting state. This indicates that the damping in the vortex state of this quasi-two-dimensional superconductor is different in character to that observed for most three-dimensional materials. Close

• 48. [Article] Pressure-induced insulating state in an organic superconductor

  The electronic-transport properties of the quasi-two-dimensional organic superconductor β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃, where BEDT-TTF stands for bisethylenedithio-tetrathiafulvalene, have been investigated ...

  Citation × Citation Citation Abstract Copy Title: Pressure-induced insulating state in an organic superconductor Author: Gard, Gary L., Mohtasham, Javid, Schlueter, J. A., Pfleiderer, C., Wosnitza, J., Hagel, J. Year: 2003 The electronic-transport properties of the quasi-two-dimensional organic superconductor β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃, where BEDT-TTF stands for bisethylenedithio-tetrathiafulvalene, have been investigated in magnetic fields up to 15 T and under hydrostatic pressure up to about 14 kbars. Shubnikov–de Haas data reveal a nonmonotonic pressure dependence of the holelike Fermi surface, a roughly linear increase of the electron g factor, and an approximately linear decrease of the cyclotron effective mass. By assuming that the latter reflects the pressure-induced reduction of the superconducting coupling parameter λ the rapid reduction of the superconducting transition temperature Tc(p) can be reasonably well described by the modified McMillan equation. Above about 12 kbars the material becomes insulating with an activated resistive behavior. This first-order metal-insulator transition has a hysteresis of about 3 kbars. This unexpected behavior is assumed to be of structural origin, although clear changes of electronic band-structure properties precede the phase transition. Title: Pressure-induced insulating state in an organic superconductor Author: Gard, Gary L., Mohtasham, Javid, Schlueter, J. A., Pfleiderer, C., Wosnitza, J., Hagel, J. Year: 2003 The electronic-transport properties of the quasi-two-dimensional organic superconductor β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃, where BEDT-TTF stands for bisethylenedithio-tetrathiafulvalene, have been investigated in magnetic fields up to 15 T and under hydrostatic pressure up to about 14 kbars. Shubnikov–de Haas data reveal a nonmonotonic pressure dependence of the holelike Fermi surface, a roughly linear increase of the electron g factor, and an approximately linear decrease of the cyclotron effective mass. By assuming that the latter reflects the pressure-induced reduction of the superconducting coupling parameter λ the rapid reduction of the superconducting transition temperature Tc(p) can be reasonably well described by the modified McMillan equation. Above about 12 kbars the material becomes insulating with an activated resistive behavior. This first-order metal-insulator transition has a hysteresis of about 3 kbars. This unexpected behavior is assumed to be of structural origin, although clear changes of electronic band-structure properties precede the phase transition. Close

• 49. [Article] Tracers of Wood Smoke

  Smoke from wood burning is a significant source of air pollution in many parts of the world. When several sources simultaneously cause air pollution, it is often difficult to determine how much comes from ...

  Citation × Citation Citation Abstract Copy Title: Tracers of Wood Smoke Author: Khalil, M. A. K., Rasmussen, R. A. Year: 2003 Smoke from wood burning is a significant source of air pollution in many parts of the world. When several sources simultaneously cause air pollution, it is often difficult to determine how much comes from wood burning. Woodsmoke has unique chemical characteristics that can be used as indicators, including elemental composition, particularly potassium and chlorine, the ratios of organic and elemental carbon, and gases such as methyl chloride. This paper deals with formulating and applying the chemical mass balance approach incorporating both gas- and aerosol-phase tracers to a study carried out at Olympia-Lacey in Washington. In this study, three types of tracers were measured simultaneously and used to estimate woodsmoke pollution during Winter, namely elemental composition and organic carbon in the particle phase and methyl chloride in the gas phase. The results from the different tracers are found to be in agreement. The air pollution at the study site was dominated by woodsmoke mostly from low-temperature combustion (about 80%), with additional but smaller contributions from oil furnaces (15%), automobiles (4%) and occasionally from other nearby sources. Title: Tracers of Wood Smoke Author: Khalil, M. A. K., Rasmussen, R. A. Year: 2003 Smoke from wood burning is a significant source of air pollution in many parts of the world. When several sources simultaneously cause air pollution, it is often difficult to determine how much comes from wood burning. Woodsmoke has unique chemical characteristics that can be used as indicators, including elemental composition, particularly potassium and chlorine, the ratios of organic and elemental carbon, and gases such as methyl chloride. This paper deals with formulating and applying the chemical mass balance approach incorporating both gas- and aerosol-phase tracers to a study carried out at Olympia-Lacey in Washington. In this study, three types of tracers were measured simultaneously and used to estimate woodsmoke pollution during Winter, namely elemental composition and organic carbon in the particle phase and methyl chloride in the gas phase. The results from the different tracers are found to be in agreement. The air pollution at the study site was dominated by woodsmoke mostly from low-temperature combustion (about 80%), with additional but smaller contributions from oil furnaces (15%), automobiles (4%) and occasionally from other nearby sources. Close

• 50. [Article] ZnO Nanoneedle/H2O Solid-Liquid Heterojunction-Based Self-Powered Ultraviolet Detector

  ZnO nanoneedle arrays were grown vertically on a fluorine-doped tin oxide-coated glass by hydrothermal method at a relatively low temperature. A self-powered photoelectrochemical cell-type UV detector ...

  Citation × Citation Citation Abstract Copy Title: ZnO Nanoneedle/H2O Solid-Liquid Heterojunction-Based Self-Powered Ultraviolet Detector Author: Li, Qinghao, Wei, Lin, Xie, Yanru, Zhang, Kai, Liu, Lei, Zhu, Dapeng, Jiao, Jun, Chen, Yanxue, Yan, Shishen, Liu, Guolei, Mei, Liangmo Year: 2013 ZnO nanoneedle arrays were grown vertically on a fluorine-doped tin oxide-coated glass by hydrothermal method at a relatively low temperature. A self-powered photoelectrochemical cell-type UV detector was fabricated using the ZnO nanoneedles as the active photoanode and H2O as the electrolyte. This solid-liquid heterojunction offers an enlarged ZnO/water contact area and a direct pathway for electron transport simultaneously. By connecting this UV photodetector to an ammeter, the intensity of UV light can be quantified using the output short-circuit photocurrent without a power source. High photosensitivity, excellent spectral selectivity, and fast photoresponse at zero bias are observed in this UV detector. The self-powered behavior can be well explained by the formation of a space charge layer near the interface of the solid-liquid heterojunction, which results in a built-in potential and makes the solid-liquid heterojunction work in photovoltaic mode. Title: ZnO Nanoneedle/H2O Solid-Liquid Heterojunction-Based Self-Powered Ultraviolet Detector Author: Li, Qinghao, Wei, Lin, Xie, Yanru, Zhang, Kai, Liu, Lei, Zhu, Dapeng, Jiao, Jun, Chen, Yanxue, Yan, Shishen, Liu, Guolei, Mei, Liangmo Year: 2013 ZnO nanoneedle arrays were grown vertically on a fluorine-doped tin oxide-coated glass by hydrothermal method at a relatively low temperature. A self-powered photoelectrochemical cell-type UV detector was fabricated using the ZnO nanoneedles as the active photoanode and H2O as the electrolyte. This solid-liquid heterojunction offers an enlarged ZnO/water contact area and a direct pathway for electron transport simultaneously. By connecting this UV photodetector to an ammeter, the intensity of UV light can be quantified using the output short-circuit photocurrent without a power source. High photosensitivity, excellent spectral selectivity, and fast photoresponse at zero bias are observed in this UV detector. The self-powered behavior can be well explained by the formation of a space charge layer near the interface of the solid-liquid heterojunction, which results in a built-in potential and makes the solid-liquid heterojunction work in photovoltaic mode. Close