The number of surface atoms on Ge(100)-(2 x 1) and Ge(111)-c(2 x 8) which contribute to the Ge3d core shift was determined by a combination of synchrotron photoemission, high-energy electron diffraction, and molecular-beam epitaxy techniques. The result was 0.87 monolayer for Ge(100)-(2 x 1), revealing that the buckled-dimer bond was primarily covalent in nature. The Ge(111)-c(2 x 8) surface exhibited "adatom" emission corresponding to 0.33 monolayer; the departure from the ideal value of 0.5 monolayer was attributed to a large number of defects on the surface.

Absolute Determination of Surface Core-Level Emission for Ge(100)-(2 x 1) and Ge(111)-c(2 x 8) - Surface Reconstruction and Defects. D.H.Rich, T.Miller, T.C.Chiang: Physical Review Letters, 1988, 60, 357-60