Effect of primary ion energy on secondary ion emission from polycrystalline surfaces

The intensity of secondary Al+, Ta+ and Zr+ ions from polycrystalline aluminium, tantalum and zirconium surfaces respectively as a function of bombarding Zn+ and Cd+ ion energies in the region of 3-10 keV has been investigated. In case of zirconium, ion emission increases steadily with bombarding ion energy, followed by an almost saturation. For Al and Ta surfaces, ion emission increases almost linearly with bombarding ion energy and then attains a broad maximum, followed by a subsequent steady decline. As far as the decreasing behaviour of secondary ion emission is concerned, rate of fall is greater in case of Ta (bcc crystal) than that in case of Al (fcc crystal). Results on cluster ion emission from aluminium under Cd+ ion bombardment are also discussed. (author)