Surface composition changes of ternary alloys in the non-steady state regime of preferential sputtering

The phenomenon of experimentally observed non-monotonic time dependencies o f the surface composition of alloys observed at sharp changes in parameters of ion irradiation (energy, flux) is considered by a proposed phenomenolog ical model. The ternary Ag-Pd-Au alloy samples of different bulk compositio n were bombarded by Ar+ ions of 2 keV energy and then the ion energy was ab ruptly changed from 2 to 5 keV. It is shown that the changes in surface com position taking place at the time intervals before the steady state regime of sputtering is reached are initiated by mass transport processes taking p lace in the bulk of the solid. At the steady state regime the surface compo sition is determined by the component sputtering yields and processes of se gregation. The matrix-dependant sputtering yields are calculated by the pro posed model. (C) 2000 Elsevier Science B.V. All rights reserved.