Transient effects during erosion of WN by deuterium ions studied with the quartz crystal microbalance technique

Transient effects during erosion of polycrystalline tungsten-nitride (WN) films by mono-energetic deuterium projectiles are studied using a quartz crystal microbalance technique. The evolution of the mass removal rate of a 360 nm thin WN film under 500 eV/D and 1000 eV/D bombardment is investigated at a temperature of 465 K in situ and in real-time as a function of the deuterium fluence. The measurements are performed at a typical flux of 1018 m−2 s−1. A strong dependency of the observed mass change rate on the deuterium fluence is found. The mass loss is initially higher than for pure tungsten (W) and drops with fluence, finally reaching the same steady state value as for pure W sputtering. Steady state surface conditions are obtained at a fluence of about 0.2 × 1023 D/m2 for 500 eV/D and 0.6 × 1023 D/m2 for 1000 eV/D. SDTrimSP simulations indicate a preferential removal of N and a corresponding W enrichment of the surface.