It was recalled that low-energy ion processing produced damaged roughened surfaces, due to the production of point defects. A study was made here of point defect production and annealing at the (001) 2 x 1 surface, during low-energy inert-ion bombardment, as a function of ion energy, ion mass, and substrate temperature. The ion-induced surface point defect production was measured in real time by using  in situ  reflection high-energy electron diffraction. The observed surface defect yield decreased abruptly at about room temperature as the substrate temperature was increased from 175 to 475K. Monte Carlo simulations of defect diffusion were developed in order to model defect recombination in the bulk and on the surface. The bulk defect distributions which were generated by a binary collision simulator were coupled to a bulk diffusion simulator in order to predict the number of ion-induced surface defects. A comparison of experimental results and simulation predictions indicated that the defects which were produced in the bulk could make an appreciable contribution to the observed surface defect yield. This also suggested that the present binary collision simulator over-estimated the depth of the defects. The simulations also indicated that the sudden fall in experimental yield, with increasing substrate temperature, did not arise from bulk defect recombination. The present Monte Carlo simulations of surface diffusion (which were applicable to any crystalline surface) supported the occurrence of a defect annealing mechanism (at low ion fluxes) which involved the surface recombination of defects that were generated within a single cascade.

B.K.Kellerman, J.A.Floro, E.Chason, D.K.Brice, S.T.Picraux, J.M.White: Journal of Vacuum Science and Technology A, 1995, 13[3], 972-8