ROLE OF NA IN THE PROMOTION OF THE GE(111) SURFACE OXIDATION

The role of Na in the promotion of the Ge(111) surface oxidation has b een studied. The sites that reacted with oxygen were recognized by the contrast change in the electron tunneling images. On the clean Ge(111 ) surface, oxidation began at the defect sites and domain boundaries. With Na on the surface, the initial oxidation also occurred at the sit es where Na adsorbed. As the oxygen dosage increased, the oxidized are a expanded laterally from the initial oxidation sites. The result indi cates that Na adsorption promoted the surface oxidation by providing e xtra oxidation centers.