Energy dependence of the sputtering yield of silicon bombarded with neon, argon, krypton, and xenon ions

Abstract

Sputtering yields of Si were determined for bombardment with Ne, Ar, Kr, and Xe ions at normal incidence in the energy range 0.2–20 keV under ultrahigh vacuum conditions (<10−7 Pa). Mass selection was employed and the energy spread was limited to a few electron volts. High fluences in excess of 1018 cm−2 were used to obtain stationary state yields. A special method was adopted for the yield determination, involving accurate current integration and eroded crater volume measurement with a micromechanical stylus. As a spinoff of the adopted technique, relative sputtering yields for Mo could also be determined. Our data agree with the sparse other recent experimental results. Discrepancies with older data sets are sizeable but can be attributed to our improved beam definition and better surface conditions. The measured yields are, even quantitatively, in surprisingly good agreement with predictions from Sigmund’s linear cascade theory in the low and intermediate energy range. At higher energy the yields fall off more rapidly than the theory predicts, the deviations increasing with decreasing projectile mass. This behavior cannot be explained entirely in terms of the parameters and assumptions entering the Sigmund model. Various proposed empirical modifications and alternatives for Sigmund’s theory are critically examined and a new quite useful simplification of the latter is derived.