NEUTRAL COPPER CLUSTER SPUTTERING YIELDS - NE+, AR+ AND XE+ BOMBARDMENT

The sputtering of neutral metal clusters was investigated by measuring relative sputtering yields of copper clusters ejected from polycrystalline copper under 3.9 keV bombardment by Ne+, Ar+ and Xe+ ions at normal incidence. The yields of clusters from Ne+ bombardment were lower than those from Ar+ bombardment, and yields from Ar+ bombardment were lower than those from Xe+ bombardment. The sputtering yield ratios Ne+/Ar+ and Xe+/Ar+ were measured to be 0.56 and 1.08. The size distribution of the sputtered clusters can be fit by a power law dependence with exponents of -8.1, -8.2 and -6.2 for Ne+, Ar+ and Xe+, respectively. The similarity of the exponents of the Ne+ and Ar+ power law fits indicates that the sputtering yields for these two primary ions are similar, while that for Xe+ is substantially higher, in contrast to the sputtering yield ratio data. The difference between the two measurements can be explained by assuming a systematic uncertainty in the sputtering yield ratio measurements that makes the measured ratios lower than the true values. Assuming a value at the high end of the experimental Ne+ sputtering yield range, the exponents of the power law fits exhibit a linear dependence on the total sputtering yield.