Mass and energy distribution of negatively and positively charged small cluster ions sputtered from GaAs(100) by 150Â keV Ar+ bombardment

Mass and energy distribution of positively and negatively charged small GaxAsy cluster ions consisting of up to six atoms sputtered from a GaAs(100) surface after 150 keV Ar+ ion bombardment are reported. Positively charged ions contain a larger fraction of Ga atoms while negatively charged ions are rich in As. Measured energy distributions display a maximum at low kinetic energies of a few eV followed by a steep decrease with increasing energy which is more pronounced for larger ions.