Synthesis of InGaZnO 4 Colloids and Its Application in a TFT Device
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1113-F09-01
Synthesis of InGaZnO4 Colloids and Its Application in a TFT Device Chen-Yu Kao1, Kan-Sen Chou1, Y.H. Yang2, and S.S. Yang2 1. Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan 30013 2. Department of Electrical Engineering, National Tsing Hua University, Hsinchu, Taiwan 30013
ABSTRACT The deposition of amorphous InGaZnO4 (a-IGZO) semiconductor film, via a sputtering process, has been demonstrated in the literature. In this paper, we present a solution method as an alternative to obtain this semiconducting film. The dispersible IGZO colloids is formed first by co-precipitation of precursors, followed by hydrothermal treatment at 200℃ for 1 hour and using CMC as the dispersion agent. The crystalline colloid would become amorphous when it was heated at above 250℃. The TFT structure was made by growing a dielectric silica layer using the CVD method, a metal layer using the sputtering method, and an active IGZO layer using the solution method. This device exhibits low operating voltage, the mobility is about 2cm2V-1s-1 and the Ion/Ioff ratio is 104. Further improvement in processing is needed.
INTRODUCTION Flexible electronics can be produced through continuous high speed printing techniques, and they possess advantages such as flexibility, lightweight, impact resistance, and low cost. Therefore, it is generally believed that flexible electronics will be important for new applications in consumer electronics [1-4]. The development of the liquid process for semiconducting material is currently focused on organic semiconductors [5-8]. However, their low mobility (10 cm2/V, as compared with a polycrystalline ZnO channel [9-14]. The purpose of this study is to demonstrate the realization of IGZO TFT whose channel layer is obtained via a solution process, which offers a simple and low-cost processing as an alternative to vacuum deposition. The IGZO nanoparticles are synthesized by
co-precipitation, followed by hydrothermal treatment. It is then dispersed as an ink using CMC (carboxymethyl cellulose) as a dispersion agent for easy applications. EXPERIMENT The atomic ratio was In:Ga:Zn=1:1:1 in this study. Indium nitrate hydrate (Alfa Aesar, USA) 0.001 mole, gallium nitrate hydrate (Alfa Aesar, USA) 0.001 mole, and zinc nitrate hexahydrate (Riedel dehaen, Germany) 0.001 mole were first dissolved in 500ml of deionized water, they were then added to a solution containing 0.02 mole NH4OH (Showa, Japan) in 500ml of deionized water. The co-precipitated material was separated by centrifuge and rinsed with deionized water three times. The gel was then dissolved in 20ml of deionized water, placed into an autoclave, and heated at 200℃ for 1 hour. The synthesized IGZO nanoparticles were then examined by X-ray diffraction (Rigaku, Japan) and SEM (Hitachi, Japan). Colloidal suspension of IGZO was prepared by adding carboxymethyl cellulose sodium salt (CMC) (Wako, Japan) as a dispersion agent. The solid content of the IGZO suspension was 10 wt%. The suspensions were then treated with ultrason
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