QUASISIMULTANEOUS SIMS, AES, AND XPS INVESTIGATIONS OF OXIDATION OF MO, TI, AND CO IN MONOLAYER RANGE

The oxidation of Mo, Ti, and Co at oxygen exposures up to several hundred Langmuirs has been investigated by combination of static SIMS, ″static″ AES (i. e. direct counting of the N (E) spectrum at low primary electron current), and XPS. The proportionally of the O(1s) and O(KLL) signals allows one to establish a coverage scale in the submonolayer range. For Mo and Ti, saturation of the Auger and O(1s) signals is reached after 4 and 9 L, respectively. The beginning surface oxidation is indicated by the successive appearance of the compound secondary ions MeO** plus or minus //n at about 2 minus 20 L. For Ti, the in-depth growth of the ″oxide″ is indicated at exposures above 8 L by the chemical shift of the Ti 2p levels, whereas for Mo no shift of the Mo(3d) levels is present up to 1000 L. Co behaves similarly to Ti, except for the higher oxygen doses needed for saturation and an additional phase at 0 minus 5 L, which is characterized by enhanced Co** plus , CoO** plus , and O** minus emission, a break in the O(1s)vs exposure curve, and an initial O(1s) level with different binding energy.