Strong composition-dependent variation of MCs+ calibration factors in TiOx and GeOx (x 2) films

The emission of MCs+ secondary ions (M designates the analyte species) from TiOx (0.2 x 2) and GeOx (0.001 x 0.8) films under Cs+ bombardment was examined. The relative calibration factors of OCs+/TiCs+ and OCs+/GeCs+ were determined and were found to depend pronouncedly on the O/Ti and O/Ge atomic concentration ratios. Specifically, with increasing oxygen content OCs+ ions form much more efficiently (as compared to TiCs+ or GeCs+ ions), an enhancement amounting to more than a factor of 10 for the highest oxygen concentrations. Concurrently, the formation of TiOCs+ or GeOCs+ ions increases drastically. For both oxide systems, an empirical relation for the oxygenconcentration dependence of the relative calibration factors could be established