Low-Energy Electron-Diffraction and Surface Conductance Studies of Surface Reaction of Germanium with Oxygen

The oxidation process of clean germanium (100), (110), and (111) surfaces was studied by simultaneously measuring the beam and background intensities of the low-energy electron-diffraction (LEED) pattern and the surface conductance during exposure of the surface to oxygen. Two distinct and separate phases of oxidation were observed. During the first phase and for the (100) and (110) surfaces, the intensity of the beams (half-order and integral) as well as that of the background decreased and reached a minimum at about 15×10−7 Torr min. The surface resistance decreased also and its minimum almost coincided with that of the beam (or background) intensity. The second phase of the oxidation was marked by an increase in resistance and beam and background intensities. Results for the (111) surface were similar, but here the minimum of surface resistance was reached after an oxygen adsorption of 200×10−7 Torr min and therefore did not coincide with the minimum of the LEED intensities. There are indications that inelastic electron processes are important and that the changes in surface conductance are related to these inelastic processes and not to the structural changes occuring at the surface during the oxidation.