Effect of grain size on defect annealing in displacement-damaged tungsten

Pulsed laser deposition and subsequent thermal treatment were used to create compact tungsten layers with various grain sizes ( 1μm, 100 nm, and 10 nm). The layers were self-damaged at room temperature up to 0.23 dpa using 20.3 MeV W ions and annealed in vacuum at 473 K or 673 K prior to exposure to deuterium plasma to populate the surviving displacement defects. Thermal desorption spectroscopy was used to measure deuterium retention and study the desorption profile. Rate-equation modeling of the desorption spectra was performed to study the behavior of individual traps at both annealing temperatures. After annealing the 1μm and 100 nm samples at 473 K, the deuterium retention was found to decrease by 24% and 9%, respectively, whereas the total deuterium retention in the 10 nm sample did not change. Annealing at 673 K reduced total deuterium retention by additional 27%, 14%, and 34% in the case of the samples with a grain size of 1μm, 100 nm, and 10 nm, respectively.