Variation of sputtering yield with fluence and temperature for Mo metal bombarded by 25 keV He ions

Abstract

In this report are described the variations of the sputtering yield of Mo with fluence up to 6 × 10 23 He-ions · m −2 and temperature up to 1200 K. The yield is saturated at fluences higher than 3 × 10 23 ions · m −2 and increases exponentially with temperature. This temperature dependence is explained in the framework of thermal sputtering theory by Kelly with a spike temperature of 6800 K, and the yield saturation is attributable to a change of the sublimation energy at the He emitting surface layer. The temperature dependence is also consistently described by replacing the elastic stopping power of Sigmund's model by the relative energy loss in a focused collision sequence of thermally vibrating lattice atoms. An empirical expression for the temperature dependence of Mo is given by Y(atoms · ion −1) = 8.1 × 10 −3exp[1.3 × l0 −3T] , for 300 K < T < 1300 K under the 25 keV He-ion bombardment.