ENERGY-LOSS AND STRAGGLING FOR 50 AND 100-KEV H-SB SURFACE( IONS PASSING THROUGH THE SI(001)2X1)

Surface stopping powers were measured for 50- and 100-keV H+ ions pass ing through the Si(001)2 X 1-Sb surface. The energy losses as a functi on of the exit angle are fit successfully by a simple relationship inv olving the time spent near the surface. The fitting parameter is in ag reement with the value expected from the bulk Sb stopping cross sectio n and the areal Sb density. This result suggests continuity of the sto pping 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 topmos t atomic layer. The estimated energy loss by surface-plasmon excitatio n 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 inci dence and the results are compared here with the bulk straggling value s.