Nanostructure Growth on Rhodium/Ruthenium by the Exposure to He Plasma

Rhodium and ruthenium thin film coatings were conducted on tungsten samples by using a magnetron sputtering device; then, we irradiated He plasma to the samples in the linear plasma device NAGDIS-II (Nagoya Divertor Simulator). Fuzzy nanostructures were formed on rhodium and ruthenium samples when the surface temperatures were ∼950 and ∼1200 K, respectively. When the surface temperature was high, i.e., >1200 K, it was found that tungsten atoms diffused across the rhodium film and reached the film surface, and tungsten-fuzz was formed over the rhodium layer. From TEM analysis of ruthenium fibers, it was identified that there were thin parts in the fibers, and some fibers had no He bubbles. It was likely that fiber growth mechanism on ruthenium was different from the other metals.