Effect of carbon and oxygen enriched layer on retention and release of deuterium implanted in tungsten and molybdenum

Retention and thermal release of D atoms implanted into W and Mo containing carbon or oxygen in the surface layers were studied by ion beam analysis t echniques. Ion implanted D atoms accumulated within the surface oxide layer on Mo and W crystals to a high concentration at room temperature, although the D distribution in the substrate crystal was not strongly affected by t he large retention in the surface. When the oxide layer was filled with a h igh density of D atoms, it was reduced by subsequent D ion implantation at room temperature and by heat treatment, especially for Mo crystals. A carbo n-enriched layer on the Mo crystal retained a large amount of D atoms and a lso significantly enhanced the D trapping in the substrate crystal at room temperature, D atoms were weakly trapped in the substrate crystal as well a s in the interface where strain fields seemed to be created simultaneously with D retention.