Work function, valence band and secondary ion intensity variations noted during the initial stages of SIMS depth profiling of Si and SiO2 by Cs |
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Authors: | PAW van der Heide FV Azzarello |
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Institution: | Center for Materials Chemistry, Department of Chemistry, University of Houston, 136 Fleming Building, Houston, TX 77204-5003, USA |
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Abstract: | Work function, valence band and 28Si− secondary ion intensity variations from various Si substrates sputtered by 1 keV Cs+ at 60° were measured. Oxide free Si wafers and native oxide terminated wafers did not reveal any appreciable valence band variations close to the Fermi edge. Their work functions however, decreased substantially with an exponential trend noted between this and Si− secondary ion intensities from the O free Si wafer. This is consistent with the electron tunneling model which assumes a resonance charge transfer process. Native oxide terminated wafers exhibited deviations from this exponential trend, while Si wafers with thicker oxides revealed the growth of sub-band features in the valence band spectra on sputtering with Cs+. These features, may partially, if not fully, explain the Cs+ induced enhancement effect noted on SiO2 substrates where work function based models are not applicable. |
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Keywords: | Ion-solid interactions Secondary ion mass spectroscopy Work function measurements Photoelectron spectroscopy Silicon Silicon oxides |
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