Backscatter currents from thin Ag films under bombardment by atomic projectiles

Abstract

Thin Ag films formed by vacuum deposition on a low Z backing material were irradiated by keV ion beams of 1H, 14N, and 40Ar. The backscatter current yield was measured with a collector plate, kept at a negative potential. For 1H, the backscatter yield increases rapidly with film thickness while for 40Ar projectiles, the yield arises mainly from a thin surface layer. The maximum depth contributing to the backscatter current yield is of the same order as the projected range in the target material. Arguments are presented that the depths involved in backscatter currents and in sputtering will be of comparable importance.