An epitaxial silicon-oxide monolayer of chemical composition of Si 2O3 (the Si2O3 layer) formed on hexagonal SiC(0001̄) surfaces has been observed by scanning tunneling microscopy (STM). Filled- and empty-state STM images with atomic resolution support the previously reported model. Typical structural defects in the Si 2O3 layer are found to be missing SiOn (n=1, 2, 3) molecules. The band gap of the Si2O3 layer obtained by point tunneling spectroscopy is 5.5±0.5eV, exhibiting considerable narrowing from that of bulk SiO2, 8.9eV. It is proposed that the Si2O3 layer is suitable as a relevant interface material for formation of SiC-based metal-oxide-semiconductor devices.
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