Position-dependent stopping power of low velocity rare gas atoms at a SnTe(001) surface

Energy losses of 15-30 keV Ne+, Ar+ and Kr+ ions specularly reflected from a SnTe(001) surface are measured. Because more than 98% of the reflected ions are neutral, the observed energy loss can be considered as the result of atom-surface interactions. From the observed energy losses; position-dependent stopping powers of the SnTe(001) surface for neutral atoms are derived. The obtained stopping powers are compared with the theory of the stopping power for low velocity ions with help of the local density approximation. While the agreement between the experimental and theoretical results is excellent for Ar and Rr atoms, the experimental stopping is about twice larger than the theoretical one for Ne atoms. This discrepancy can be explained in terms of the effect of excited atoms on the stopping power. (C) 1999 Elsevier Science B.V. All rights reserved.