Observations of orientation dependence of surface morphology in tungsten implanted by low energy and high flux D plasma

Surface modification by formation of blistering and nanostructures with pronounced orientation dependence has been observed on surfaces of rolled tungsten and recrystallized tungsten after exposure to a low energy (38 eV) deuterium (D) plasma with a high flux of 10²⁴ m^-2 s ^-1. The correlation between blisters and nanostructures with grain orientation was examined on recrystallized tungsten to exclude the influence of defects introduced during plastic deformation on the pattern of surface modification. The amount of blistering changed from the most in grains oriented close to 〈1 1 1〉 to the least in grains oriented close to 〈0 0 1〉. Three kinds of typical nanostructures were observed, with a clear dependence on grain orientation. Triangular structures were observed on grains oriented near the 〈1 1 1〉 corner of the inverse pole figure, with lamellar structures formed for grains oriented near the 〈0 1 1〉 corner, and spongy structures for grains near the 〈0 0 1〉 corner. Possible reasons for the orientation dependence of both the blisters and nanostructures are discussed.