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 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 (<900 K), fuzz does not grow because almost all He is
trapped in very small He-vacancy clusters. At high 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.