Bombardment induced surface damage in a nickel single crystal observed by ion scattering and leed

In an experiment which combines ion scattering at low energies and low energy electron diffraction (LEED)the influence of Ar+ ion bombardment on the structure of a Ni (110) single crystal surface is investigated. At an energy of 1 keV Ar+ ion scattering from an undisturbed single crystal face is governed by multiple scattering which can be described by sequences of binary collisions. Computer simulations of the scattering process show that by introducing surface defects changes in the backscattering spectra occur. The surface damage from the ion beam gives indeed rise to increasing binary scattering, thereby decreasing multiple scattering. These changes are observable above 1015 ions/cm2. The results suggest the production of point defects and extended defect structure. This is in qualitative agreement with the measurement of the widths of LEED spots, where the widths increase and become asymmetric with increasing dose. The production of point defects reaches saturation at 1016 ions/cm2, at the dose rate applied.