DETERMINATION OF THE SURFACE BINDING ENERGY OF A Cu/Li ALLOY BY MEASUREMENTS OF ANGULAR DISTRIBUTION OF SPUTTERED ATOMS

A copper based binary alloy containing 16.9 at % lithium has been bombarded with deuterium ions in energy range of 400 eV to 2 keV at the incidence angles of 70° and 80° away from the surface normal. The sputtered flux was condensed on Al- strips arranged arround the target in a cylindrical cup. 1.5 MeV proton backscattering and nuclear reaction 7Li(p, α)4He were used to detect the collected atoms of Cu and Li simultaneously. The angular distribution of sputtered atoms has been shown to be different for two components and strongly anisotropic for the grazing incidence. According to direct knock-on sputtering model and the experimental results the angle for the maximum differential sputtering yield is dependent on the incidence angle α, the bombarding energy E, the energy transfer factor γ= 4M1M2/(M1+ M2)2 and the surface binding energy U. With the assumption that the sputtered particles are diffracted by a planar barrier the surface binding energies of 2.3 eV for the Li component and 3.0 eV for the Cu component have been determined by fitting the measured angles of preferred ejection to the direct knock-on sputtering model, and the results agree well with a pair-binding model.

DETERMINATION OF THE SURFACE BINDING ENERGY OF A Cu/Li ALLOY BY MEASUREMENTS OF ANGULAR DISTRIBUTION OF SPUTTERED ATOMS