SPM Characterization of Substrate Surfaces Prepared for Carbon-Related-Film Deposition
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SPM Characterization of Substrate Surfaces Prepared for Carbon-Related-Film Deposition Kazumasa Narumi, Shunya Yamamoto 1 and Hiroshi Naramoto Takasaki Branch, Advanced Science Research Center, JAERI, 1233 Watanuki-machi, Takasaki, Gunma, 370-1292, Japan 1 Department of Materials Development, JAERI, 1233 Watanuki-machi, Takasaki, Gunma, 370-1292, Japan ABSTRACTS Variation of surface steps on sapphire (0001) and (11¯20) substrates processed with thermal annealing in air or a reducing environment at 1000 to 1400 °C for 1 to 10 hours were investigated with an atomic force microscope (AFM). The annealed (0001) surfaces consist of atomically smooth and large terraces and atomic-height steps, whose configurations strongly depend on annealing conditions. On the (11¯20) surfaces, where crystallographic misorientation is almost an order of magnitude larger than that of the (0001) surfaces, step height and terraces increase in size with the longer annealing time and higher annealing temperature. Characteristic step figures due to the symmetry of atomic arrangement were observed on the (0001) surface. INTRODUCTION Since the success of diamond synthesis by chemical vapor deposition (CVD) [1], many groups have done extensive investigation into diamond thin films. For epitaxial growth of diamond on diamond substrates, films of quite high quality has been obtained [2], while sufficiently uniform epitaxial films has not been obtained yet in the case of heteroepitaxially grown films which is important technique for future application in diamond device technology. Although many candidate substrates for the heteroepitaxy of diamond have been selected from the various viewpoints [3], any systematic consideration has not been paid to control the substrate surface except for pretreatment to promote nucleation. Sapphire has been used as a substrate for thin-film deposition because of its high purity, high chemical stability and high crystal quality and is now widely used for fabrication of the blue-emitting device [4]. From the viewpoint of the diamond epitaxial growth, sapphire may be promising: Recently, Yoshimoto et al. succeeded in epitaxial diamond growth on the (0001) surface of sapphire under an oxidizing environment [5]. From their results, one can reasonably deduce that one of the important keys to the epitaxial growth is to prepare an atomically smooth sapphire surface by controlled annealing in air [6]: on an as-received substrate, the grown crystals are not arranged in plane. They showed a possibility to design the surface features of the sapphire substrate in an atomic scale such as the smooth-terrace width and the atomic step height by controlling the misorientation from the crystallographic axis and the annealing condition [6]. In the present study, we investigate the surface morphology changes on sapphire substrates with an atomic force microscope by focusing on surface steps after systematic thermal annealing. O8.4.1
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