Surface-induced optical anisotropy of oxidized, clean, and hydrogenated vicinal Si(001) surfaces

We report surface-induced optical anisotropy (SIOA) spectra obtained by reflectance-difference spectroscopy (RDS) of several vicinal Si(001) surfaces. Chemically (RCA) cleaned surfaces show sharp, step-induced, derivative-like features that increase with vicinal angle. The RD signal for these surfaces can be modeled as an anisotropy that is localized to the surface and can be described in terms of a dichroic bandgap. The spectra of clean reconstructed surfaces show both a broad structure near 3 eV, which appears to involve dimer dangling bond transitions, and a second feature near 4.3 eV that occurs near the E2 peak of bulk Si. The difference between spectra of the 10° and 6° vicinal samples yields a resultant signal similar to that of Si(113). We also report the RD signal for the monohydride and dihydride phases for the hydrogenated surfaces.