SURFACE PERIODICITIES OF HIGH-INDEX FACETS ON VICINAL SI(111)

The concave surface of mechanochemically treated Si(111) samples break s up, under UHV treatment, into a large number of vicinal Si(111) surf aces. The concave surface presents a continuous range of polar angles up to 10-degrees for arbitrary azimuthal direction. Scanning tunneling microscopy (STM) measurements, performed on different parts of the su rface, have shown facetting into (111)-oriented, 7 X 7 reconstructed t erraces, steps or step bunches. Characteristic step arrangements known from individually prepared vicinal Si(111) surfaces have been identif ied. On step bunches ordered regions with orientations corresponding t o high-index (hkl) values have been observed. One of these could be as signed to a (9 13 7) facet and is decribed in the present work.