Application of the Ion Bombardment Cleaning Method to Titanium, Germanium, Silicon, and Nickel as Determined by Low-Energy Electron Diffraction

The ion-bombardment cleaning method has been successfully applied to the (100) faces of germanium, silicon, and nickel, and to the (0001) face of titanium. Conditions and precautions necessary for the production of clean surfaces are described. Tests have been made for contamination from the ambient during the cleaning procedure for germanium. It has been shown that contamination approximating one-half monolayer does not occur under the conditions which were obtained, and that the method is capable of producing surfaces which are atomically clean. Results for clean (100), (111), and (110) germanium faces and the (100) silicon face indicate that the atomic positions in the surface planes are not the same as the corresponding positions in the bulk structure. For (100) nickel and (0001) titanium, the positions of the atoms in the surface planes are in agreement with x-ray data. In the case of titanium, an unidentified surface structure was present until after several cycles of alternate heating and ion bombardment. In the case of nickel, a double-spaced surface monolayer and in some cases a single-spaced, simple-square structure, attributed to carbon, was present until after several cycles of alternate heating and ion bombardment.