Temperature dependence of underdense nanostructure formation in tungsten under helium irradiation

Recently, tungsten has been found to form a highly underdense nanostructured morphology (“W fuzz”) when bombarded by an intense flux of He ions, but only in the temperature window 900–2000 K. Using object kinetic Monte Carlo simulations (pseudo-3D simulations) parameterized from first principles, we show that this temperature dependence can be understood based on He and point defect clustering, cluster growth, and detrapping reactions. At low temperatures (2300 K), all He is detrapped from clusters, preventing the formation of the large clusters that lead to fuzz growth in the intermediate temperature range. •OKMC simulation of temperature window for fuzz formation.•Stable He-V clusters prevent fuzz formation at low temperatures.•Dissociation of He-V clusters prevent fuzz formation at high temperatures.•Fuzz formation rate increases with increasing temperature.•An incubation fluence observed in the simulations, similar to experimental observations.