Continuous observation of surface erosion of polycrystalline molybdenum implanted with helium ions with different energies

Surface erosion of polycrystalline molybdenum caused by helium ion bombardment, with various irradiation modes of different energies ranged from 60 to 200 keV, was studied by continuous observation of the surfaces under helium ion bombardment. The development processes of the surface deformation are presented as a function of irradiation dose and the critical fluence for surface deformation was precisely determined. The critical helium concentrations for blistering were obtained from the calculated profiles of implated helium at the critical fluence and it was found that the critical concentrations for both 100 and 200 keV single implantation were almost the same, whereas the critical concentrations for sequential irradiation were distributed around that for a single implantation. In addition, it was observed that the average thickness of the exfoliated layer lay nearly at the peak in the depth profile.