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Surface Structures and Surface Processes of Ceramics With Atomic Resolution-A Study by Scanning Tunneling Microscopy

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Final rept. 1 Jun 1988-30 Sep 1991

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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 B-SiC100 and 111, which showed a variety of reconstructions. In particular, the STM images of the B-SiC111 surface showed a 6 x 6-geometry, in contrast to a 6 3 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 B-SiC111 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.

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  • Physical Chemistry
  • Ceramics, Refractories and Glass
  • Laminates and Composite Materials
  • Solid State Physics

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