Sputtering of tungsten, tungsten oxide, and tungsten-carbon mixed layers by deuterium ions in the threshold energy region

An original experimental method is developed for determining the sputtering coefficients of electrically conducting materials during bombardment by li ght gas ions at threshold energies. This information is very valuable in bo th purely scientific and practical terms. The basis of the method is a spec ial field-ion-microscopic analysis regime. The procedure for measuring the sputtering coefficients includes cleaning the surface by field desorption a nd evaporation, with the subsequent work on an atomically clean and atomica lly smooth surface. The method permits identification of single vacancies o n the irradiated surface, i.e., it is possible to count individual sputtere d atoms. The method is tested on commercially pure tungsten, tungsten oxide , and a W-C mixed layer on tungsten under deuterium ion bombardment. The en ergy dependences of the sputtering coefficients of these materials for sput tering by deuterium ions at energies of 10-500 eV are obtained and analyzed . An important relationship between the energy threshold for sputtering and the conditions for oxidation of tungsten is found. The energy threshold fo r sputtering of an oxidized tungsten surface is 65 eV. The energy threshold for sputtering of the W-C mixed layer is almost equal to the corresponding value for pure tungsten. (C) 1999 American Institute of Physics. [S1063-78 42(99)02909-8].