Absolute Determination of Surface Core-Level Emission for Ge(100)-(2×1) and Ge (111)−c(2×8): Surface Reconstruction and Defects

The number of surface atoms on Ge(100)-(2X I) and Ge(111)-c(2X8)which contribute to the Ge 3d core shift is determined by a combination of synchrotron photoemission, high-energy electron diffraction, and molecular-beam epitaxy techniques. The result is 0.87+0.09 monolayer for Ge(100)-(2&&1), revealing that the buckled-dimer bond is primarily covalent in nature. The Ge(111)-c(2X8) surface
shows "adatom" emission corresponding to 0.33 ~ 0.04 monolayer; the departure from the ideal value of 0.5 monolayer is attributed to a large number of defects on the surface.