Sputtering yield increase with fluence in low-energy argon plasma-tungsten interaction

The increase of tungsten sputtering yield with fluence was investigated during plasma (≤100 eV) irradiation. This analysis focused on the combined effects of surface binding energy and surface morphology caused by Ar retention. As post-mortem analysis, Ar concentration was measured with SIMS (Secondary Ion Mass Spectroscopy) and TDS (Thermal Desorption Spectroscopy). The Ar concentration saturated at 21 % of W number density during the sputtering process. The corresponding change in surface morphology causes a change in the local ion incident angle, which leads to a sputtering yield increase of 10 %. The increased Ar concentration leads to a decrease in surface binding energy and a change in surface morphology which increases W sputtering yield from 0.02 to 0.03 by ion energy 80 eV. Over time, W sputtering yield reaches saturation as a function of saturated Ar concentration. This result implies that the synergistic role of Ar concentration and surface morphology on sputtering yield. This sputtering yield enhancement occurs more seriously in the realistic condition of plasma-facing materials that face low-energy plasma.