Carbon contamination free Ge(100) surface cleaning for MBE

A carbon free wet treatment for Ge(100) surface has been proposed. This treatment consists of three steps: (1) several cycles of surface oxidation with H2O2 solution and the oxide etching with HCl solution, (2) the formation of protective oxide by NH4OH/H2O2/H2O treatment and (3) thermal desorption of the protective oxide in ultra high vacuum. An atomic force microscope image of the Ge(100) surface after step (1) indicates the surfaces is very smooth. After step (2), it is confirmed that the protective oxide contains no carbon contamination by Auger electron spectroscopy measurement. A reflection high energy electron diffraction pattern indicates that the surface, after step (3), has only atomic-scale steps.