Surface Structures and Surface Processes of Ceramics with Atomic Resolutions - AStudy by Scanning Tunneling Microscopy

摘要

We applied a new technique for surface imaging, scanning tunneling microscopy(STM) to study the atomic and electronic structures of ceramic surfaces. The model ceramic chosen for this study was SiC. STM imaging was possible when the SiC single crystals were doped with nitrogen to render them semiconducting. Atomically resolved images were successfully taken on surfaces of cubic Beta-SiC(100) and (111), which showed a variety of reconstructions. In particular, the STM images of the Beta-SiC(III) surface showed a 6 x 6 geometry, in contrast to a 643 x 6 3 geometry when measured by low-energy electron diffraction (LEED). We found that this discrepancy was due to a graphite monolayer incommensurately grown on top of the Si-terminated Beta-SiC(Ill) surface. This conclusion was reached after probing the electronic structure of the surface by scanning tunneling spectroscopy (STS). On a larger scale, i.e. over distances between 50 nm and 500 nm, the surface topographics observed by STM were correlated with the initial growth modes of the SiC simple crystals. In addition to the STM studies, we conducted experimental and theoretical investigations on the thermochemistry and interfacial displacement reactions of the Ti-Si-C and Ti-Si-N systems in order to refine the understanding of thermodynamic and phase equilibria characteristics of ceramic-metal composite systems.