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 0.65±0.09 eV and 0.50±0.05 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.

• Received 3 September 1991

DOI:https://doi.org/10.1103/PhysRevB.44.13791