SURFACE ELECTRONIC STATES OF LOW-TEMPERATURE H-PLASMA-EXPOSED GE(100)

The surface of low-temperature H-plasma-cleaned Ge(100) was studied by angle-resolved UV-photoemission spectroscopy and low-energy electron diffraction (LEED). The surface was prepared by an ex situ preclean followed by an in situ H-plasma exposure at a substrate temperature of 150-300-degrees-C. Auger-electron spectroscopy indicated that the in situ H-plasma clean removed the surface contaminants (carbon and oxygen) from the Ge(100) surface. The LEED pattern varied from a 1 X 1 to a sharp 2 X 1, as the substrate temperature was increased. The H-induced surface state was identified at approximately 5.6 eV below E(F), which was believed to be mainly due to the ordered or disordered monohydride phases. The annealing dependence of the spectra showed that the hydride started to dissociate at a temperature of 190-degrees-C, and the dangling-bond surface state was identified. A spectral shift upon annealing indicated that the H-terminated surfaces were unpinned. After the H-plasma clean at 300-degrees-C the dangling-bond surface state was also observed directly with no evidence of H-induced states.