By comparing the C 1s photoemission intensities from a clean diamond {111} surface to those obtained from a fluorine-covered surface, we conclude that a single t, '111) layer of atoms participates in the diamond 2X 1 surface reconstruction. The data interpretation presented does not rely on assuming an electron mean free path, but, in fact provides an independent measurement of its value. For clean diamond (111) a surface core-level peak is observed at 0.80+0.05 eV lower binding energy than the bulk-C 1s peak at 285.0 eV below E~. After fluorine exposure a single chemically shifted carbon peak is observed at 1.85+0.05 eV higher binding energy than the bulk peak, indicating the presence of CF units at the surface.
High resolution core level spectroscopy with synchrotron radiation is used to determine the bonding at the epitaxial CaF2/Si (111) interface. It is found that both Ca and F bond to Si at the interface inducing core level shifts of +0.4 eV and −0.8 eV, respectively. Structural models with an atomically sharp interface are proposed where Ca bonds to the first layer Si and F to the second layer.
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