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Surface oxidation reactions of cobalt, molybdenum and mixed cobalt-molybdenum metals have been investigated using x-ray pbchelectron spectroscopy (XPS). Tbe oxide stoicbiometries have been determined from XPS intensity measurements Sucb quantification has been important in identifying oxide compositions with cbaracteristic XPS spectra. A number of discrete binary molybdenum oxides have been characterized after reactions at 2OOOC and pressures ranging from 1 atm to Pa. At the lowest pressure, the Mo 3d spectra and O/Mo ratias suggest the formation of a molybdenum-oxygen structure with a stoicbiometry oear unity. By contrast, at bigber presa~ures, oxides that are predominantly MOO, and MOO, appear, but other intermediate oxide structures are also identified. Wellde6ned binary oxides of cobalt can be prepared from cobalt metal after beating in oxygen at merent pressures. New binary oxides of cobalt and molybdenum have been generated by the reaction on MOO, or c0#4 substrates. Oxidation of a tbin film of molybdenum on a Co,O, substrate bas been shown to produce a nearly stoichiometric rrurface layer of CoMd), . The procedure could be wieful for the production of other ternary oxides of possible interest for use as XPS reference materials.

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The nanoindentation-induced phase transformation behavior of silicon at elevated temperatures (25-150 degrees C) has been studied. Nucleation of Si-III/Si-XII on unloading is enhanced with increasing temperature and at the highest temperatures in an amorphous Si matrix, occurs in a continuous fashion without a pop-out event. Interestingly, for slow unloading at the highest temperatures, formation of Si-III/Si-XII in a crystalline Si matrix was not observed. Elevated temperatures enhance the nucleation of Si-III and Si-XII during unloading but the final composition of the phase transformed zone is also dependent on the thermal stability of the phases in their respective matrices.