Inert gas ion bombardment induced work function changes in polycrystalline tungsten and gold ribbon

Abstract

Polycrystalline tungsten and gold ribbon targets were bombarded with low-energy (100eV–600eV) inert gas ions of helium, argon and krypton. The thermionic work function of the target was monitored before and after bombardment by a retarding potential field method in a diode valve with the target as the anode. Work function recovery was monitored during post-bombardment step annealing studies. Bombardment-induced work function increases of several tenths of an electron volt in tungsten were recovered in annealing stages corresponding to surface vacancy migration and gas releasefrom the surface regions. Smaller work function reductions in gold targets were annealed in stages corresponding to damage diffusion, normal diffusion and gas bubble diffusion processes.