Secondary ion formation/survival during the initial stages of sputtering Si and SiO2 with Cs+

Secondary ion intensities, substrate composition, work function and valence band spectra during the initial stages of sputter depth profiling Si and SiO2 with 1 keV Cs+, along with ion induced Auger emissions resulting from 1 keV Xe+ have been studied. The results reveal that the increasing O−, Si−, and Si2− intensities and decreasing Si+ and Cs+ intensities noted with increasing Cs+ dose from Si substrates, stems primarily from a Cs induced reduction of the work function. Similar intensity variations were noted from SiO2 substrates. These appear to be due to sub-band states introduced during sputtering. Such trends, along with the matrix dependent transient effects observed in the secondary ion emissions from both Si and SiO2, are consistent with resonance charge transfer as being the primary process responsible for secondary ion formation/survival. Minor deviations from the expected trends suggest the presence of Auger de-excitation (Si+ and Cs+) and variable poly-atomic formation (Si2−) probabilities.