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• 1. [Article] Low-temperature, Inkjet-printed p-Type Copper(I) Iodide-based Thin-Film Transistors

  Inkjet-printed p-type copper(I) iodide-based TFTs were successfully fabricated. As-printed copper(I) halide semiconductor films, such as CuI, CuBrI, and CuClI, were used as p-type active channel layers ...

  Citation × Citation Citation Abstract Copy Title: Low-temperature, Inkjet-printed p-Type Copper(I) Iodide-based Thin-Film Transistors Author: Gorecki, Jenna Y. Inkjet-printed p-type copper(I) iodide-based TFTs were successfully fabricated. As-printed copper(I) halide semiconductor films, such as CuI, CuBrI, and CuClI, were used as p-type active channel layers for TFTs. The entire process of the TFTs fabrication was maintained under 150 °C, which is compatible with flexible plastic substrates and transparent glass substrate. Various printing temperatures, drop spacing, W/L ratios, and TFT structures were tested in order to find the optimum device properties for p-type copper(I) iodide-based TFT. In addition, inkjet-printed CuI, CuBrI, and CuClI films were characterized to study optical, electrical, and morphological properties. Furthermore, device performance of printed copper(I) iodide-based p-type TFTs was also investigated. Among them, CuI TFTs with SU-8 encapsulation exhibited outstanding p-type transistor behaviours with field-effect mobility as high as 4.36 cm² V⁻¹ s⁻¹ and Ion/Ioff ratio of 103.24 on the silicon substrate. Also, CuBrI TFTs resulted in successful p-type transistor behaviours with average field-effect mobility of 2.4 cm² V⁻¹ s⁻¹ and I[subscript on]/I[subscript off] ratio of 101.9 on the glass substrates when the molar ratio of CuBr:CuI was 1:1. In addition, CuClI TFTs were successfully fabricated with field-effect mobility as high as 1.02 cm² V⁻¹ s⁻¹ and I[subscript on]/I[subscript off] ratio of 10⁰·⁷³ on the silicon substrates when the molar ratio of CuCl:CuI was 1:9. The device performances were comparable to reported p-type metal oxide TFTs. This study suggests promising candidates of low-temperature printed p-type TFTs that can be used for complementary inorganic circuits. Title: Low-temperature, Inkjet-printed p-Type Copper(I) Iodide-based Thin-Film Transistors Author: Gorecki, Jenna Y. Inkjet-printed p-type copper(I) iodide-based TFTs were successfully fabricated. As-printed copper(I) halide semiconductor films, such as CuI, CuBrI, and CuClI, were used as p-type active channel layers for TFTs. The entire process of the TFTs fabrication was maintained under 150 °C, which is compatible with flexible plastic substrates and transparent glass substrate. Various printing temperatures, drop spacing, W/L ratios, and TFT structures were tested in order to find the optimum device properties for p-type copper(I) iodide-based TFT. In addition, inkjet-printed CuI, CuBrI, and CuClI films were characterized to study optical, electrical, and morphological properties. Furthermore, device performance of printed copper(I) iodide-based p-type TFTs was also investigated. Among them, CuI TFTs with SU-8 encapsulation exhibited outstanding p-type transistor behaviours with field-effect mobility as high as 4.36 cm² V⁻¹ s⁻¹ and Ion/Ioff ratio of 103.24 on the silicon substrate. Also, CuBrI TFTs resulted in successful p-type transistor behaviours with average field-effect mobility of 2.4 cm² V⁻¹ s⁻¹ and I[subscript on]/I[subscript off] ratio of 101.9 on the glass substrates when the molar ratio of CuBr:CuI was 1:1. In addition, CuClI TFTs were successfully fabricated with field-effect mobility as high as 1.02 cm² V⁻¹ s⁻¹ and I[subscript on]/I[subscript off] ratio of 10⁰·⁷³ on the silicon substrates when the molar ratio of CuCl:CuI was 1:9. The device performances were comparable to reported p-type metal oxide TFTs. This study suggests promising candidates of low-temperature printed p-type TFTs that can be used for complementary inorganic circuits. Close

• 2. [Article] Investigation of low temperature solution-based deposition process for flexible electronics

  The critical contribution of this dissertation is to provide a better understanding of the fundamental Chemical Bath Deposition (CBD) growth kinetic and mechanism for the well known II-VI semiconductor ...

  Citation × Citation Citation Abstract Copy Title: Investigation of low temperature solution-based deposition process for flexible electronics Author: Chang, Yu-Jen The critical contribution of this dissertation is to provide a better understanding of the fundamental Chemical Bath Deposition (CBD) growth kinetic and mechanism for the well known II-VI semiconductor CdS using the newly developed continuous flow microreactor. This continuous flow microreactor provides the temporal resolution to control the homogeneous reaction of the chemical solution before it impinges on the substrate surface. This capability was used to decouple the homogeneous particle formation and deposition from the molecular level heterogeneous surface reaction to overcome the drawbacks associated with a conventional batch process. Transmission electron microscopy (TEM) analysis indicated an impinging flux without the formation of nanoparticles which could be obtained from this reactor in a short residence time. In addition, the reactor could be operated in a homogeneous particle formation regime. Size increasing CdS nanoparticles grown by homogeneous reaction were clearly observed from TEM and SEM micrographs by increasing the residence time from 1 to 280 sec using pre-heated precursor solutions. The formation of CdS nanorod and arrayed nanorod bundle structures using the CBD recipe were also observed in some areas and reported here for the first time. The growth kinetics were studied using a particle-free flux. The deposition results suggest that HS− ions formed through the thiourea hydrolysis reaction are the dominant sulfide ion source responsible for the CdS deposition rather than thioura itself that had been widely discussed in almost all of the previous literature. This finding could not be observed previously by a conventional CBD batch setup because all the reactant solutions were sequentially pulled into the reaction beaker and mixed all at once. An impinging flux without the formation of nanoparticles enables us to deposit extremely smooth and highly oriented nanocrystalline CdS semiconductor thin films at low temperature (80°C). Enhancement-mode functional thin film transistors with an effective mobility of μ[subscript eff] =1.46 cm²/V s, drain current on-to-off ratio of approximately 10⁵ and turn-on voltage at 0 V were fabricated from the asdeposited films without any post annealing process. This microreactor could be adapted for the deposition of other compound semiconductor thin films such as highly transparent amorphous Indium Oxide (In₂O₃) thin films at low temperature (70°C) using chemical solution deposition and opens a low-cost avenue to fabricate thin film flexible electronics on polymeric substrates. Title: Investigation of low temperature solution-based deposition process for flexible electronics Author: Chang, Yu-Jen The critical contribution of this dissertation is to provide a better understanding of the fundamental Chemical Bath Deposition (CBD) growth kinetic and mechanism for the well known II-VI semiconductor CdS using the newly developed continuous flow microreactor. This continuous flow microreactor provides the temporal resolution to control the homogeneous reaction of the chemical solution before it impinges on the substrate surface. This capability was used to decouple the homogeneous particle formation and deposition from the molecular level heterogeneous surface reaction to overcome the drawbacks associated with a conventional batch process. Transmission electron microscopy (TEM) analysis indicated an impinging flux without the formation of nanoparticles which could be obtained from this reactor in a short residence time. In addition, the reactor could be operated in a homogeneous particle formation regime. Size increasing CdS nanoparticles grown by homogeneous reaction were clearly observed from TEM and SEM micrographs by increasing the residence time from 1 to 280 sec using pre-heated precursor solutions. The formation of CdS nanorod and arrayed nanorod bundle structures using the CBD recipe were also observed in some areas and reported here for the first time. The growth kinetics were studied using a particle-free flux. The deposition results suggest that HS− ions formed through the thiourea hydrolysis reaction are the dominant sulfide ion source responsible for the CdS deposition rather than thioura itself that had been widely discussed in almost all of the previous literature. This finding could not be observed previously by a conventional CBD batch setup because all the reactant solutions were sequentially pulled into the reaction beaker and mixed all at once. An impinging flux without the formation of nanoparticles enables us to deposit extremely smooth and highly oriented nanocrystalline CdS semiconductor thin films at low temperature (80°C). Enhancement-mode functional thin film transistors with an effective mobility of μ[subscript eff] =1.46 cm²/V s, drain current on-to-off ratio of approximately 10⁵ and turn-on voltage at 0 V were fabricated from the asdeposited films without any post annealing process. This microreactor could be adapted for the deposition of other compound semiconductor thin films such as highly transparent amorphous Indium Oxide (In₂O₃) thin films at low temperature (70°C) using chemical solution deposition and opens a low-cost avenue to fabricate thin film flexible electronics on polymeric substrates. Close