Photofragmentation of semiconductor positive cluster ions

Si, Ge, and GaAs positive cluster ions containing up to sixty atoms have been prepared by laser vaporization and supersonic beam expansion and their laser photofragmentation studied using tandem time‐of‐flight mass spectrometry. The fragmentation pattern observed for GaAs is very similar to that observed for metal clusters and is consistent with the sequential loss of atoms. Si and Ge clusters appear to fragment by a fission process, Sin + fragments primarily into positive ions in the 6–11 size range with a subsidiary channel corresponding to loss of a single atom. Gen + also gives clusters in the 6–11 size range at relatively high fluence and has a channel corresponding to loss of a single atom at low fluence. At intermediate fluences, channels corresponding to sequential loss of Ge10 and Ge7 are observed.