High Performance ITO Nanoparticles as Nanoink for Printing as a Substitute Process of Sputtering
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High Performance ITO Nanoparticles as Nanoink for Printing as a Substitute Process of Sputtering Atsushi Muramatsu,1 Kiyoshi Kanie, 1 Takafumi Sasaki, 2 Masafumi Nakaya1 1 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University 2 Mitsui Mining & Smelting Co., Ltd.
ABSTRACT Generally, indium-tin-oxides (ITO) thin film is prepared by the sputtering process with ITO target, but only 20% of ITO yielded from the target is deposited on the substrate. Namely, about 80% ITO is exhausted by the deposition elsewhere far from the substrate. The recycling process is limited so that ca 20% ITO of the starting target is lost without any recovery. Even if the recycling of ITO has been carried out in this process, we should prepare ITO target of 5 times more than apparent use of ITO on film. If we change it to printing process from the sputtering, the reduction in ITO use is expected as ca. 50%, considering the increase in film thickness by printing. Our target technology also includes ITO nanoink for the project. As a result, monodispersed ITO nanoparticles (NPs) with a cubic shape were fabricated by using quaternary ammonium hydroxide-assisted metal hydroxide organogels. These NPs have perfect uniformity in size with beautiful shape, and perfect single crystalline structure including Sn. As we were attempted to make thin film with ITO nanoink, it was successfully fabricated below 200 nm in thickness and the resistivity was drastically decreased below 1.0 x 10-3 cm after heat treatments. GZO nanoink as substitute of ITO has also been developed. INTRODUCTION Toyoha Mine in Sapporo, Japan, had supplied Indium as a top of world, was closed on March 31, 2006. Before that, METI (Ministry of Economy, Trade and Industry, Japan) and Tohoku Univ. had started to discuss the project on substitute materials development of indium from 2004. Indium is well known to use as indium-tin-oxides (ITO) materials for transparent conductive oxides (TCO), which is often used in devices such as a flat panel display, touch-panel, solar cell, etc. ITO thin film is prepared by the sputtering process with ITO target, but only 20% of ITO yielded from the target is deposited on the substrate. Namely, about 80% ITO is exhausted by the deposition elsewhere far from the substrate. The recycling process is limited so that ca 20% ITO of the starting target is lost without any recovery. Even if the recycling of ITO has been carried out in this process, we should prepare ITO target of 5 times more than apparent use of ITO on film. If we change it to printing process from the sputtering, the reduction in ITO use is expected as ca. 50%, considering the increase in film thickness by printing. As a result, our target technology included the development of ITO nanoink for this project. ITO nanoink was the next important technology for Japan, since the concept of printed electronics by use of nanoink has recently accepted as a novel engineering to make a functional thin film and/or advanced electronic circuits. Moreover, ITO film prepared by ink
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