Xe Bubble Formation in Xe-Implanted Fe as Observed by the Channelling Method.

In order to investigate the initial stage of Xe bubble formation in α-Fe, the lattice location of Xe atoms has been studied by the channelling method for the Fe crystals implanted with Xe ions at 150 keV at room temperature up to doses 10 14 , 4×10 14 , 10 15 and 10 16  Xe/cm 2 . Most of the Xe atoms are located at substitutional ( S ) and random ( R ) sites. At low implantation doses small portion of them are located at tetrahedral ( T ) sites and the sites slightly displaced from a lattice point by about 0.085 nm in the direction ( D site). With increasing implantation dose the fractions of S -, D - and T -site occupancies decrease, whereas that of the R -site occupancy increases. These results suggest that at the initial stage of implantation Xe-vacancy ( V ) complexes, i.e., Xe V , Xe V 4 and larger ones, are formed and they act as nucleation centres for the subsequent growth to Xe bubbles.