Band gap of the Ge(111)2×1 and Si(111)2×1 surfaces by scanning tunneling spectroscopy

The scanning tunneling microscope is used to measure the spectrum of states for the Ge(111)2×1 and Si(111)2×1 surfaces. Detailed spectra, revealing the entire empty and filled state bands for both surfaces are obtained. Band gaps of 0.650.09 eV and 0.500.05 eV are found for the Ge and Si surfaces, respectively. The results are compared with values for the band gaps obtained from recent quasiparticle calculations. © 1991 The American Physical Society.