TEM study on deuterium-irradiation-induced defects in tungsten and molybdenum

Deuterium-irradiation-induced defects in tungsten (W) and molybdenum (Mo) were examined by transmission electron microscopy (TEM). The observed defects were perfect dislocation loops of interstitial type with the Burgers vector of a/2 〈1 1 1〉 type. The loop plane has non-integer Miller indices nearly parallel to the {1 1 0} plane. Subsequent growth of some dislocation loops was observed during further irradiation with W by post-irradiation of 1 MeV electrons in a high-voltage electron microscope. This growth is ascribed to the dissociation of SIA-D complexes (SIA: self-interstitial atom, D: deuterium) and subsequent absorption of the released interstitial atoms by nearby dislocation loops.