Scanning tunnelling microscopy of diamond deposition at the nanometre scale holes on highly orientated pyrolytic graphite

摘要

Recently, (100) highly textured diamond thin films were successfully synthesized on Si(10 0) [1], but complete heteroepitaxial diamond films have not yet been synthesized. This is because the mechanisms of nucleation and growth of diamond by chemical vapour deposition (CVD) are not fully understood. To clarify the mechanism of the nucleation process at the various nucleation sites, continuous observa-tion of the nucleation and growth process in the same area, ideally in situ observation, is required. Scanning tunnelling microscopy (STM) is one of the candidates for this purpose, since STM uses a microscope with atomic resolution which can be operated in various environments, even in CVD conditions. Moreover, STM can also be used for atomic scale spectroscopy (scanning tunnelling spectroscopy) [2] and for the fabrication of nano-metre scale structures [3]. For these reasons, STM is expected to be applied not only to the observation of the nucleation process but also to the fabrication of artificial nucleation sites. STM observations of nucleation in diamond CVD have been reported [4, 5]; however, roughened Si wafers scratched by diamond powder have been used exclusively as the substrates. In addition, different areas were observed before and after the depositions. Therefore, it has been impossible to correlate the nucleation process and nucleation sites so far, although information about growth on the nanometre scale have been reported. In this letter, we report the observation of diamond nucleation in a hot-filament assisted CVD process at the nanometre scale holes fabricated artificially on highly orientated pyrolytic graphite (HOPG) by STM.