SECONDARY-ION INVERSE VELOCITY PLOTS FROM A CAMECA IMS-3F SIMS INSTRUMENT

Transmission function calculations for a Cameca IMS-3f secondary ion m ass spectrometer have allowed for the measurements of inverse velocity (1/nu) plots for Cu+ and Cu-secondary ions emitted from a Cu substrat e over the 6-250 eV (plus binding energy) emission energy range. Stron g linear relationships were exhibited in these plots, particularly ove r the higher energy portion (> 80 eV). Such trends indicate an exponen tial dependence of the secondary ion yield on emission velocity, consi stent with current surface ionisation theories. At energies below 80 e V deviations from this trend were observed particularly for the Cu-sec ondary ions. Comparison with 1/nu plots for ions (F+ and H+) known to be produced, to some extent, via a stimulated desorption process, sugg ests that the lower energy deviation exhibited by the Cu- secondary io ns results from a desorption process. The possibility of near surface collisions is also considered.