Ion-induced erosion of tungsten surfaces studied by a sensitive quartz-crystal-microbalance technique

A highly sensitive quartz-crystal-microbalance (QCM) technique was used to study erosion of polycrystalline tungsten films due to impact of deuterium, carbon and argon ions, as well as retention of deuterium in these films. Polycrystalline tungsten films coated onto a SC-cut quartz crystal were bombarded by ions with impact energies from 100 eV up to a few keV and the frequency change due to mass loss (sputtering, desorption) or mass gain (implantation, adsorption) during bombardment was determined. Our setup was capable of detecting mass-changes as small as 10−5 μg/s, which corresponds to a removal (or deposition) of only 10−4 W monolayers/s. While our total sputtering yields for deuterium and argon projectiles compare well with the results of previous work, we derive new data on sputtering of tungsten by carbon ions. In addition we demonstrate that our setup is well suited for determining deuterium retention rates in tungsten.