The effect of orientation on ion beam erosion rates in ionic crystals measured by SIMS depth profiling

There are reports in the literature that crystal orientation is a major source of variation in sputter yields when examining biomineralized tissue material. To examine this further, single crystals of fluorapatite and calcite, both mineralogical analogues, were examined with two different SIMS machines, an Atomika 2000 and a Cameca IMSA4F. Craters were eroded on planes parallel to (0001) and (1010) of both samples for different lengths of time, at different angles and with different primary ion beams. Instruments were operated at a voltge of 10 or 15 kV for Cs+ and O2+, respectively, and a primary beam current of 200 nA. The erosion times were such that all sites were exposed to high fluences of 1018 ions cm−2. For a given experimental geometry and primary ion beam, there wee no discernible differences in erosion rates due to crystal orientation. It is believed that this is due to amorphization of the crystal surface at the target site by site by ion bombardment at high fluences. Therefore, we conclude that crystal orientation is not a significant factor in variation of sputter yield in the materials investigated, and suggest that in biomineralized tissue material the development of surface topography is due to other factors.