| Co-Investigator(Kenkyū-buntansha) |
FUYUKI Takashi Nara Institute of Science and Technology, Material Science, Professor, 物質創成科学研究科, 教授 (10165459)
HATAYAMA Tomoaki Nara Institute of Science and Technology, Material Science, Assistant Professor, 物質創成科学研究科, 助手 (90304162)
YANO Hiroshi Nara Institute of Science and Technology, Material Science, Assistant Professor, 物質創成科学研究科, 助手 (40335485)
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| Budget Amount *help |
¥14,800,000 (Direct Cost: ¥14,800,000)
Fiscal Year 2006: ¥7,900,000 (Direct Cost: ¥7,900,000)
Fiscal Year 2005: ¥6,900,000 (Direct Cost: ¥6,900,000)
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| Research Abstract |
Polycrystalline silicon (poly-Si) films fabricated on glass or plastic substrates have attracted much attention due to their applications in thin-film transistors (TFT) for flat-panel displays or future displays, such as a system-on-panel. In this study, we propose a new method utilizing biotechnology to obtain high-quality poly-Si thin films. As the nucleus of silicon crystallization, the Ni core of ferritin with a diameter of 7 nm was adsorbed on the surface of a-Si films by a bottom-up process. By adjusting the density of ferritin on the a-Si film, we controlled the Ni nucleus density and performed the solid-phase crystallization of the a-Si film.
The a-Si film with a controlled crystal nucleus was heated up to 550℃in 10 min and then annealed for 25 h in N_2 ambient in an RTA furnace. Rapid heating suppresses the generation of a natural nucleus and poly-Si growth proceeds laterally from the controlled nucleus of NiSi_2. It is reported that the activation energies of Ni/a-Si → NiSi_2,
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a-Si → crystalline Si, and the generation of a natural nucleus are 1.45, 2.7, and 4.4eV, respectively. Therefore, it is estimated that the rapid heating and continuous annealing at 550℃ enhanced the reaction of NiSi_2 dominantly, thus the crystal growth of poly-Si proceeded.
Furthermore, to examine grain size and crystalline orientation, EBSD analysis was performed. The "grains" were defined as the regions with the same crystallographic orientations and the same phases. Mapping images showed that definite grains were not observed at a density of 10^<11>cm^<-2>, therefore, the microcrystalline structure was dominant. For the film with a density of 10^<10>cm^<-2>, a mixture of grains and a microcrystalline structure was confirmed. However, for the film with a core density of 10^9cm^<-2>, definite grains were confirmed and their size was uniform. The orientations of the grains were random in all samples. The film without cores prepared as reference had no grains. The average grain sizes estimated from the size distribution, were 0.36 a m, 0.48 it m and 3.06 μm for the core densities of 10^<11>, 10^<10> and 10^9 cm^<-2>, respectively. Thus, grain size increased markedly with decreasing core density. Less
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