Single-crystal sputtering including the channeling phenomenon

Abstract

Measurements of the angular behavior of the sputtering ratio for Ar+ on (100) Cu turned around a [011] axis are presented for Ar+ energies of 5, 10, 15, 20, and 35 keV. It is shown that the widths of the [100] minima can be related to the acceptance angle for channeling, as described by the theory of Lindhard. This is taken as evidence for the assumption that a channeled particle does not contribute to sputtering. On the basis of the assumption that the sputtering ratio is proportional to the energy dissipation of the nonchanneled part of the beam within a layer x0, a two-parameter expression for the sputtering ratio has been obtained.Calculations have been performed for normally incident Ar+, Kr+, and Cu+ ions on (111), (110), and (100) Cu crystals in the energy range 2–40 keV. The best fit has been obtained for x0 values of the order of 80 Å. From the description of Ar+ on (100) Au, x0 is about 135 Å. This is thought to be due to the influence of the focusing collision chain length on the thickness of the layer important for sputtering. Furthermore, it is shown that a satisfactory description of the angular behavior of the sputtering ratio can be obtained with the proposed model.