Energy loss and straggling for 50- and 100-keV H+ ions passing through the Si(001)2x1-Sb surface

Surface stopping powers were measured for 50- and 100-keV H+ ions passing through the Si(001)2 X 1-Sb surface. The energy losses as a function of the exit angle are fit successfully by a simple relationship involving the time spent near the surface. The fitting parameter is in agreement with the value expected from the bulk Sb stopping cross section and the areal Sb density. This result suggests continuity of the stopping power from the bulk to the surface. It provides a useful method for determining the distance between the plane of deposited atoms and of a substrate surface and for measuring the composition of the topmost atomic layer. The estimated energy loss by surface-plasmon excitation is negligibly small in the present system. The energy straggling as a function of exit angle was also measured for 50- and 100-keV Ht incidence and the results are compared here with the bulk straggling values.