ION-BEAM EFFECTS ON THE SURFACE AND NEAR-SURFACE COMPOSITION OF TASI2

Low-energy (0.7-4.5 keV) ion bombardment effects on polycrystalline TaSi2 at sputter steady state and in various intermediate steps have been investigated, in the temperature range up to 550-degrees-C, to determine the time and temperature dependence of the altered layer formation. This in turn enables a better knowledge of the synergistic effects of the processes mentioned above. At low temperatures (T less-than-or-equal-to 410-degrees-C) the surface is silicon depleted, and the depletion is even more severe in the subsurface region up to a depth of several tens of angstroms; silicon preferential sputtering and radiation-enhanced segregation assisted by the displacement mixing-induced motion of atoms are assumed to be responsible for this composition profile, while thermally activated diffusion processes become operative above 410-degrees-C, reducing progressively the concentration gradient between the surface and the subsurface zone. The composition at different depths has been determined from Auger peaks of different kinetic energies, by varying the take-off angle and finally by sputter profiling at low ion energy the high energy processed surfaces. Quantitative analysis has been performed by XPS and AES by using the elemental standard method. by XPS and AES by using the elemental standard method.