Fabrication of Electrically Active Si-based Thin Films by Pulsed Laser Deposition of SiO/C Dual Targets
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1148-PP03-39
Fabrication of Electrically Active Si-based Thin Films by Pulsed Laser Deposition of SiO/C Dual Targets Yusaburo Ono1, Yushi Kato1, Yasuyuki Akita1, Makoto Hosaka1, Naoki Shiraishi1, Makoto Yamaguchi2, Osami Sakata3, and Mamoru Yoshimoto1 1 Department of Innovative & Engineered Materials, Tokyo Institute of Technology, 4259-J2-46, Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan. 2 OSAKA Titanium technologies Co., Ltd., Higashihama-cho, Amagasaki, Hyogo 660-8533, Japan. 3 Japan Synchrotron Radiation Research Institute/ SPring-8, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
ABSTRACT We investigated the fabrication of Si nanocrystals, including thin films, by annealing the SiO/C/SiO thin films in an Ar atmosphere. The SiO/C/SiO trilayered thin films were deposited on α-Al2O3 (0001), Si (111), or ITO-coated borosilicate glass substrates at room temperature by pulsed laser deposition using dual sintered SiO (molar ratio Si/O of 1/1) and graphite targets. The SiO/C/SiO thin films subjected to heat treatment at 500oC included nanocrystalline Si. Measurements by synchrotron radiation X-ray diffraction indicated the formation of Si nanocrystals having a size of 5–10 nm. Fourier transform infrared spectra showed that Si–O stretching and vibrational peak intensities of the as-deposited thin film decreased remarkably after annealing. The C layer in the SiO/C/SiO trilayered thin films is considered to play a role in enhancing the chemical reaction that produces Si nanocrystals through reduction of SiO during heat treatment. The annealed SiO/C-based thin films, including Si nanocrystals, exhibited photosensitive conduction behavior in current–voltage measurements.
INTRODUCTION Development of semiconductor electronic devices is attributed to great progress in science and technology of Si-based materials. For example, Si materials have been applied to solar cells and integrated circuits. Furthermore, SiO2 materials have been used as gate insulating layers for TFTs because of their insulation performance, durability, solvent resistance, and gas barrier properties, which have been widely studied [1]. On the other hand, Si-rich or oxygen-poor SiOx (1 ≤ x < 2) thin films are used as insulating or dielectric layers in Josephson junction circuits [2] and metal–insulator–semiconductor (MIS) tunnel diodes [3]. Since the early reports of photoluminescence from porous Si and Si nanocrystals in 1990 [4, 5], Si nanocrystals have been fabricated by various techniques, including ion implantation of Si into SiO2 [6, 7], magnetron sputtering using Si and SiO2 targets [8, 9], laser ablation of Si targets [10-12], and thermal evaporation of SiOx powders [13, 14]. Recently, nanocrystalline Si quantum dots/a-SiC multilayers have been prepared by thermal annealing of a-SiC:H/silicon-rich a-Si1-xCx multilayers, and their possible application to solar cells has been reported [15-17].Silicon raw material has also been industrially produced in electric furnaces by the carbothermal reduction of silica (SiO2), as in the following reac
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