Generation of large indium clusters by sputtering

Abstract

We have investigated the yields of neutral and charged ${\mathrm{In}}_{n}$ clusters sputtered from a pure indium surface under bombardment with 15-keV ${\mathrm{Xe}}^{+}$ ions. It is shown that large neutral clusters containing up to 200 atoms can be detected. If the measured signals are corrected for size-dependent detection efficiency, an inverse power-law yield distribution according to ${n}^{\ensuremath{-}\ensuremath{\delta}}$ is found which exhibits two decay exponents of -3.9 for small $(n<~20)$ and -2.1 for large $(20<~n<~100)$ clusters. This finding closes the gap between published mass spectrometric and electron microscopy data on the size distributions of sputtered clusters. It also indicates that the generation of large clusters in sputtering is governed by hydrodynamical or even thermodynamical mechanisms rather than the fast collisional processes leading to the emission of small clusters.