Sputtering of beryllium, tungsten, tungsten oxide and mixed W-C layers by deuterium ions in the near-threshold energy range

摘要

An experimental method of determination of sputtering yield for current-conducting materials under ion bombardment of light gases in the near-threshold energy range has been developed. Such an information is very important in both the purely scientific and applied aspects. This method is based on the use of special regimes of field ion microscopic analysis. The procedure of measuring the sputtering yield includes cleaning of the surface in situ by desorption and evaporation of atoms by the field in order to make atomic-clean and atomic-smooth surface. This method permits to observe single vacancies in the irradiated surface, i.e., directly to count the single sputtered atoms. It has been used for beryllium, technically pure tungsten, tungsten oxide and mixed W-C layer on the tungsten irradiated by deuterium ions. The energy dependence of sputtering yield of those materials by deuterium ions at energies ranging from 10 to 500 eV is investigated. Experimental results for beryllium are in a satisfactory agreement with the calculations of Eckstein et al. Substantial connection between threshold energy of the sputtering and condition of oxidized surface of tungsten has been ascertained. The threshold energy for sputtering of oxidized tungsten surface is equal to 65 eV. The threshold energy for sputtering of mixed W-C layer has almost the same value as for the pure W.