SPUTTERING OF NEUTRAL AND IONIC INDIUM CLUSTERS

Secondary neutral and secondary ion cluster yields were measured during the sputtering of a polycrystalline indium surface by normally incident approximately 4 keV Ar+ ions. In the secondary neutral mass spectra, indium clusters as large as In32 were observed. In the secondary ion mass spectra, indium clusters up to In18+ were recorded. Cluster yields obtained from both the neutral and ion channel exhibited a power law dependence on the number of constituent atoms n in the cluster, with the exponents measured to be -5.6 and -4.1, respectively. An abundance drop was observed at n = 8, 15, and 16 in both the neutral and ion yield distributions, suggesting that the stability of the ion (either secondary ion or photoion) plays a significant role in the observed distributions. In addition, our experiments suggest that unimolecular decomposition of the neutral cluster may also play an important role in the measured yield distributions.