Gas cluster ion beam source for secondary ion emission measurements

Abstract

This chapter discusses the gas cluster ion beam source for secondary ion emission measurements. When solids are bombarded with cluster ions, collision cascades induced by individual constituent atoms of the cluster overlap each other. Energy density deposited with cluster ions is much higher than that deposited with monomer ions at the same velocity. Thus, subsequent phenomena, such as material modifications or secondary particle emissions, are enhanced under the impact of ‘n’- atom clusters compared to the sum over ‘n’ atomic ions. These enhancements are generally called "nonlinear effects". The feature of secondary ion yield as a function of primary beam energy could be compared for monomer and cluster impacts. For monomer impacts the emission of ionized species has similarities with the emission of neutral species, showing that these processes proceed by a common mechanism. For large cluster impacts, the sputtering yield increases linearly with the primary ion energy.