Band gap of the Ge(111)c(2x8) surface by scanning tunneling spectroscopy

Abstract

The surface band gap of the Ge(111)c(2x8) surface at low temperature is determined on the basis of scanning tunneling spectroscopy. Electrostatic potential computations permit evaluation of tip-induced band bending, from which a correction to the energy scale of the observed spectra is made. Parameter values in the computations are constrained by comparison of the observed spectrum with known spectral features, including high-lying conduction band features derived from first-principles computations. The surface band gap, lying between the bulk valence band maximum and the minimum of an adatom-induced surface band, is found to have a width of 0.49 +/- 0.03 eV.