Argon ion sputtering of niobium and niobium alloys

Abstract

Polycrystalline niobium was irradiated by a beam of 15-keV argon ions, and the effect of certain metallurgical and environmental conditions was studied. Macroscopic sputtering yields were measured for well-annealed niobium and also for Nb--V and Nb--O alloys, cold-worked and recovered niobium and for sputtering conducted in an oxygen atmosphere. In all cases, the resulting surface topography was characterized by scanning electron microscopy. Selected area electron channeling patterns were used to determine the texture of the annealed niobium and to correlate sputter-induced surface features with grain orientations. The surface chemistry of sputtered targets was checked with a scanning Auger microprobe. Results indicate that ion channeling and surface mobility are important in the 15-keV argon sputtering of niobium. The sputtering yield for annealed niobium was accurately described by modifying a sputtering theory for amorphous solids through use of a correction factor based on ion channeling which was calculated from the experimentally determined texture. The sputter topography was varied and, at times, complex. Surface features were dependent on crystallography, background pressure, temperature and the metallurgical conditions of cold work, recovery, annealing, interstitial solute and precipitation structure. The sputtering yield was also determined to be a function of the metallurgical conditions, the crystallography, and pressure. 62 figures, 10 tables.