PHOTOELECTRON SPECTROSCOPIC INVESTIGATIONS OF THE SURFACE REACTIVITY OF CRYSTALLINE AND AMORPHOUS TI-CU ALLOYS

The surface reactivity of in-situ co-condensed crystalline and amorphous TiCu2 alloys has been compared in the present study; the extent of reactivity of the samples was examined by X-ray photoelectron spectroscopy (XPS) after annealing at high vacuum and reacting the surface with 0.67 Pa (5 x 10(-3) Torr) of oxygen at pre-selected temperatures. The amorphous Ti-Cu alloy exhibited higher initial surface reactivity by forming oxidized titanium more readily. At intermediate temperatures (300-400-degrees-C), continued oxidation of both alloys led to the formation of titanium oxide overlayers such that there was a minimal amount of surface copper. Annealing in high vacuum to 600-degrees-C led to the decomposition of Ti2O3 and TiO2 on both alloys; however, the small amount of copper detectable by XPS remained metallic. At higher oxygen pressures, the complete oxidation of surface titanium to TiO2 occurred at 400-degrees-C for the amorphous alloy, and at 500-degrees-C for the crystalline state. It was after this point that the underlying metallic copper underwent oxidation to Cu1+ and diffused to the surface region through the titanium oxide overlayer. These findings are discussed in terms of observed differences between the surface oxidation behavior of crystalline and amorphous Ti-Cu alloys.