Temperature dependence of the total sputtering yield of a two-phase [formula omitted] ( [formula omitted]) alloy for 200 eV Ar + ions

Abstract

The total sputtering yield of a Ag Cu two-phase alloy ( 65 35 at% ) as a function of temperature (−54° C to 123° C) for 200 eV Ar + at normal incidence has been measured. For a fluence of approximately 10 20 ions/cm 2, the total yield was a maximum at low temperature and decreased as the temperature was increased until at the highest temperature, the yield was approximately one half the value at the lowest temperature. At high temperature, SEM revealed that the surface was covered with a dense “forest” of microscopic cone-like structures, whereas at low temperature the cones were absent and the surface had a more faceted appearance. At higher temperatures it is believed that bombardment enhanced surface diffusion facilitates the formation of cones and ridges. Under continued sputtering the aspect ratio of these features increases until it is large enough to allow recapture of material ejected from valleys and neighboring features. For samples sputtered at elevated temperatures, this redeposition appears to be responsible for the significant lowering of the total yield. The results did not depend on the method of target fabrication (three different methods were tested). To simplify the yield calculations, it was assumed that component ejection was stoichiometric with the bulk for the entire bombardment time. The validity of this simplification is discussed.