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Book Investigation of Indium Titanium Zinc Oxide Thin Film Transistors Fabricated by RF Sputtering System and Their Optoelectronic Application

Download or read book Investigation of Indium Titanium Zinc Oxide Thin Film Transistors Fabricated by RF Sputtering System and Their Optoelectronic Application written by 吳韋廷 and published by . This book was released on 2017 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Investigation of Indium Zinc Oxide Thin Film Transistors Fabricated by Sputtered System and Their Optoelectronic Application

Download or read book Investigation of Indium Zinc Oxide Thin Film Transistors Fabricated by Sputtered System and Their Optoelectronic Application written by 溫承樺 and published by . This book was released on 2014 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book An Investigation of the Performance and Stability of Zinc Oxide Thin film Transistors and the Role of High k Dielectrics

Download or read book An Investigation of the Performance and Stability of Zinc Oxide Thin film Transistors and the Role of High k Dielectrics written by Ngwashi Divine Khan and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Transparent oxide semiconducting films have continued to receive considerable attention, from a fundamental and application-based point of view, primarily because of their useful fundamental properties. Of particular interest is zinc oxide (ZnO), an n-type semiconductor that exhibits excellent optical, electrical, catalytic and gas-sensing properties, and has many applications in various fields. In this work, thin film transistor (TFT) arrays based on ZnO have been prepared by reactive radio frequency (RF) magnetron sputtering. Prior to the TFT fabrication, ZnO layers were sputtered on to glass and silicon substrates, and the deposition parameters optimised for electrical resistivities suitable for TFT applications. The sputtering process was carried out at room temperature with no intentional heating. The aim of this work is to prepare ZnO thin films with stable semiconducting electrical properties to be used as the active channel in TFTs; and to understand the role of intrinsic point defects in device performance and stability. The effect of oxygen (O2) adsorption on TFT device characteristics is also investigated. The structural quality of the material (defect type and concentration), electrical and optical properties (transmission/absorption) of semiconductor materials are usually closely correlated. Using the Vienna ab-initio simulation package (VASP), it is predicted that O2 adsorption may influence film transport properties only within a few atomic layers beneath the adsorption site. These findings were exploited to deposit thin films that are relatively stable in atmospheric ambient with improved TFT applications. TFTs incorporating the optimised layer were fabricated and demonstrated very impressive performance metrics, with effective channel mobilities as high as 30 cm2/V-1s-1, on-off current ratios of 107 and sub-threshold slopes of 0.9? 3.2 V/dec. These were found to be dependent on film thickness (~15? 60 nm) and the underlying dielectric (silicon dioxide (SiO2), gadolinium oxide (Gd2O3), yttrium oxide (Y2O3) and hafnium oxide (HfO2)). In this work, prior to sputtering the ZnO layer (using a ZnO target of 99.999 % purity), the sputtering chamber was evacuated to a base pressure ~4 x 10-6 Torr. Oxygen (O2) and argon (Ar) gas (with O2/Ar ratio of varying proportions) were then pumped into the chamber and the deposition process optimised by varying the RF power between 25 and 500 W and the O2/Ar ratio between 0.010 to 0.375. A two-level factorial design technique was implemented to test specific parameter combinations (i.e. RF power and O2/Ar ratio) and then statistical analysis was utilised to map out the responses. The ZnO films were sputtered on glass and silicon substrates for transparency and resistivity measurements, and TFT fabrication respectively. For TFT device fabrication, ZnO films were deposited onto thermally-grown silicon dioxide (SiO2) or a high-k dielectric layer (HfO2, Gd2O3 and Y2O3) deposited by a metal-organic chemical deposition (MOCVD) process. Also, by using ab initio simulation as implemented in the?Vienna ab initio simulation package (VASP)?, the role of oxygen adsorption on the electrical stability of ZnO thin film is also investigated. The results indicate that O2 adsorption on ZnO layers could modify both the electronic density of states in the vicinity of the Fermi level and the band gap of the film. This study is complemented by studying the effects of low temperature annealing in air on the properties of ZnO films. It is speculated that O2 adsorption/desorption at low temperatures (150? 350 0C) induces variations in the electrical resistance, band gap and Urbach energy of the film, consistent with the trends predicted from DFT results.

Book Development of Indium Gallium Zinc Oxide Thin Film Transistors on a Softening Shape Memory Polymer for Implantable Neural Interfaces Devices

Download or read book Development of Indium Gallium Zinc Oxide Thin Film Transistors on a Softening Shape Memory Polymer for Implantable Neural Interfaces Devices written by Ovidio Rodriguez Lopez and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The continuous improvement in electronic active devices has led to several innovations in semiconductor materials, novel deposition methods, and improved microfabrication techniques. In the same way, the implementation of thin-film technology has revolutionized the semiconductor industry. For instance, the field of flexible electronics has utilized novel thin-film electronics components for the fabrication flexible displays, radio frequency identification (RF-ID) tags, and solar cells. Moreover, flexible electronics have sparked a great interest in the field of bioelectronics, for the fabrication of high-spatial-resolution implantable devices for neural interfaces. This incorporation of thin-film technology can potentially enable stimulation and recording the nervous system activity by utilizing novel, minimally invasive, conformal devices. To achieve this, flexible electronics circuits must possess high performance, reliability, and stability, as well as be resilient to mechanical stress and human body conditions, are some of the requirements that flexible electronics must meet for the realization of these devices. Furthermore, the choice of substrates is also critical since it directly affects final properties of the active devices. Substrates, which are mechanically and biologically compliant, are preferred. For this reason, novel, softening materials like thiol-ene polymers are considered in this research. This work centers on the development of Indium-Gallium-Zinc-Oxide (IGZO) thin-film transistors (TFT) using the thiol-ene softening polymer as substrate. Functional IGZO-TFTs were fabricated on top of 50 μm of a thiol-ene/acrylate shape memory polymer (SMP) and electrically characterized. Hafnium oxide (HfO2) deposited at 100°C by atomic layer deposition was used as gate dielectric, and gold (Au) as contacts. The devices were exposed to oxygen, vacuum and forming gas (FG) environments at 250°C to analyze the effects of these atmospheres on the IGZO-TFTs. Improvement in the electrical performance was noticed after the exposure to FG with a significant change in mobility from 0.01 to 30 cm2 V-1s-1, and a reduction in the threshold voltage shift (∆Vth), which it is translated into an increase on stability. Vacuum and oxygen effects were, also analyzed and compared. Furthermore, a time-dependent dielectric breakdown (TDDB) analysis was performed to define the lifetime of the transistors, where a prediction of 10 years at an operational range below 5 V was obtained. Additionally, the TFTs were encapsulated with 5 μm of SMP and exposed to simulated in vivo conditions. Up to 104 bending cycles were performed to the IGZO-TFTs with a bending radius of 5 mm and then, soaked into PBS solution at 37°C for one week to determine the resilience and reliability of the devices. The encapsulated IGZO-TFTs survived to the PBS environment and demonstrated resilience to mechanical deformation with small changes in the electronic properties. The results provided in this research contribute to the development of complex circuitry based on thin-film devices using mechanically adaptive polymers as a flexible substrate and enable the production of multichannel implantable bioelectronics devices.

Book Thin film Transistors Fabricated Using Sputter Deposition of ZnO

Download or read book Thin film Transistors Fabricated Using Sputter Deposition of ZnO written by Nan Xiao and published by . This book was released on 2013 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Development of thin film transistors (TFTs) with conventional channel layer materials, such as amorphous silicon (a-Si) and polysilicon (poly-Si), has been extensively investigated. A-Si TFT currently serves the large flat panel industry; however advanced display products are demanding better TFT performance because of the associated low electron mobility of a-Si. This has motivated interest in semiconducting metal oxides, such as Zinc Oxide (ZnO), for TFT backplanes. This work involves the fabrication and characterization of TFTs using ZnO deposited by sputtering. An overview of the process details and results from recently fabricated TFTs following a full-factorial designed experiment will be presented. Material characterization and analysis of electrical results will be described. The investigated process variables were the gate dielectric and ZnO sputtering process parameters including power density and oxygen partial pressure. Electrical results showed clear differences in treatment combinations, with certain I-V characteristics demonstrating superior performance to preliminary work. A study of device stability will also be discussed."--Abstract.

Book Fabrication and Characterization of Oxide based Thin Film Transistors and Process Development for Oxide Heterostructures

Download or read book Fabrication and Characterization of Oxide based Thin Film Transistors and Process Development for Oxide Heterostructures written by Wantae Lim and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: This dissertation is focused on the development of thin film transistors (TFTs) using oxide materials composed of post-transitional cations with (n-1)d10ns0 (n[more than or equal to]4). The goal is to achieve high performance oxide-based TFTs fabricated at low processing temperature on either glass or flexible substrates for next generation display applications. In addition, etching mechanism and Ohmic contact formation for oxide heterostructure (ZnO/CuCrO2) system is demonstrated. The deposition and characterization of oxide semiconductors (In2O3-Zn0, and InGaZnO4) using a RF-magnetron sputtering system are studied. The main influence on the resistivity of the films is found to be the oxygen partial pressure in the sputtering ambient. The films remained amorphous and transparent (> 70%) at all process conditions. These films showed good transmittance at suitable conductivity for transistor fabrication. The electrical characteristics of both top- and bottom-gate type Indium Zinc Oxide (InZnO) and Indium Gallium Zinc Oxide (InGaZnO4)-based TFTs are reported. The InZnO films were favorable for depletion-mode TFTs due to their tendency to form oxygen vacancies, while enhancement-mode devices were realized with InGaZnO4 films. The InGaZnO4-based TFTs fabricated on either glass or plastic substrates at low temperature (

Book Optimization of the Fabrication Condition of RF Sputtered ZnO Thin Film Transistors with High k HfO2 Gate Dielectric

Download or read book Optimization of the Fabrication Condition of RF Sputtered ZnO Thin Film Transistors with High k HfO2 Gate Dielectric written by Prem Thapaliya and published by . This book was released on 2016 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional amorphous silicon based thin film transistors have been the most widely used ones for flat panel display application during the last two decades. However, the low mobility of less than 1 cm2/Vs and light induced instability of the amorphous silicon based thin film transistor make them unsuitable for high resolution displays. Oxide based thin film transistors have attracted a great deal of interest as an alternative to conventional amorphous silicon based thin film transistors for high resolution display applications. In particular, ZnO has gained considerable interest for the next generation transparent and flexible display due to its wide band gap of 3.37 eV, high electron mobility and low temperature deposition forming good quality of polycrystalline film even at room temperature. Consequently all the aforementioned features of ZnO make them promising channel material for the flexible and transparent TFTs. The electrical characteristics of ZnO based TFTs is greatly affected by the deposition condition and hence crystalline quality of channel layer, thickness of channel layer and quality of interface between the gate dielectric and the channel layer. Therefore, the deposition temperature and the thickness of the ZnO channel needs to be optimized in order to achieve high performance ZnO TFTs. Moreover, the quality of interface between the ZnO channel layer and the gate dielectric is of vital importance to improve the performance of the TFTs. In this dissertation, we have fabricated and characterized RF sputtered ZnO based thin film transistor using high-k HfO2 gate dielectric. The transparent ZnO TFTs was realized using FTO as a transparent gate electrode as opposed to commonly used ITO gate electrode. It was found that TFTs fabricated using the FTO gate electrode showed lower mobility and on/off ratio compared to the TFTs with Ru as a gate on the Si substrate. This deterioration of TFTs performance with the use of FTO gate electrode was attributed to the degradation of HfO2 gate dielectric due to the diffusion of fluorine from the FTO into the HfO2 during its deposition at 300 °C. In order to minimize the interface trap density at the interface between the ZnO and HfO2, an interfacial layer of MgO with different thickness was investigated. It was found that 10 nm MgO is an optimum thickness that can reduce the interface trap density by almost one order of magnitude and hence exhibit the best TFTs performance with field effect mobility, threshold voltage, on/off ratio and subthreshold swing to be 0.3 cm2/V.s, 3.7 V , 106 and 1.35 V/decade respectively. The decrease in the interface trap density with the interfacial layer was attributed to the reduction of defects in the ZnO by the excess oxygen ions of MgO. Furthermore, the ZnO channel layer was deposited at different temperature including room temperature, 50 °C, 100 °C and 200 °C, to determine the optimum deposition temperature that can achieve high performance ZnO TFTs. It was found that ZnO deposited at 50 °C showed the best TFT performance with field effect mobility, threshold voltage, on off ratio and subthreshold swing 1.12 cm2/V.s, 5.8 V, 1.4×105, 1.35 V/decade respectively. The improvement in the performance of the TFTs device with 50 °C ZnO was attributed to the low surface roughness of ZnO film, increased grain size and good polycrystalline quality which was confirmed with the help of XRD, AFM and SEM measurement of ZnO thin film deposited at different temperature. Likewise, once the optimum deposition temperature of ZnO was determined, the effect of ZnO thickness was investigated by depositing the ZnO with different thickness including 30 nm, 50 nm, 70 nm and 100 nm while maintaining the deposition temperature of ZnO to be at 50 °C. It was found that the TFTs device with 50 nm exhibit the superior performance over the other thicknesses of ZnO which was ascribed to the improved polycrystalline quality, low surface roughness of the 50 nm ZnO thin film.

Book Investigation of Optical and Electrical Properties of Gallium Zinc Tin Oxide GaZTO Thin Film Transistors by RF Sputter and Its Optoelectronic Application

Download or read book Investigation of Optical and Electrical Properties of Gallium Zinc Tin Oxide GaZTO Thin Film Transistors by RF Sputter and Its Optoelectronic Application written by 許至淳 and published by . This book was released on 2018 with total page 89 pages. Available in PDF, EPUB and Kindle. Book excerpt: