THE INFLUENCE OF POLARIZABILITY ON THE EMISSION OF SPUTTERED MOLECULAR-IONS

Bombardment of solid surfaces by Cs+ ions results in the emission of m olecular secondary ions of the type MCs(+) where M denotes an element contained in the sample. For a variety of semiconductors the yield Y o f these species exhibits a quadratic dependence on the polarizability of the atom M, Y proportional to alpha(n) and n approximate to 2. The experiments support a MCs(+) formation mechanism via the association o f a Cs+ ion and a neutral M atom. Using a potential of the form V(r)=A r-12-0.5 alpha e(2)r(-4) to model this dimer interaction, the yield de pendence on a observed experimentally can be reproduced, establishing thus the key role which the polarizability of M plays in the formation of MCs(+) molecular ions.