Copper single crystal sputtering in the temperature range from 50K to 600K

Abstract

Measurements are performed on the dependence of the sputtering ratio of monocrystalline copper on the target temperature, for bombardment on (100), (110) and (111) crystals with 20 keV Ar⁺ or Ne⁺ ions at normal incidence. The target temperatures are varied roughly from 50 K to 600 K. These bombardments along a low index direction are compared with bombardment in an opaque direction. A model is sketched to calculate the influence of the thermal vibrations on the channeling effect. Two effects are considered: broadening of the string and blocking of the channel. It leads to an expression for the fraction of the ion beam that dechannels as a function of the depth. Assuming an expression for the sputtering efficiency from a certain depth in the crystal, the sputtering ratio can be calculated. In the case of the (100) and (110) crystals the calculations agree reasonably well with the measurements. Comparing calculation and experiment it can be concluded, that the maximum depth responsible for sputtering decreases with increasing temperature. For the (111) direction no satisfactory description according to the sketched model can be given. This can be explained by the relatively narrow [111] channels.