We have studied the reproducibility of electron spectra obtained from a series of Si(111) surfaces on lightly doped crystals that were subjected to a common sputtering procedure but different subsequent heat treatments. Each of the surfaces displayed a sharp 7 × 7 LEED pattern and showed no impurities above the minimum detection limit of our Auger electron spectrograph. Ion neutralization spectroscopy (INS) and photoemission (UPS) at ℏω = 16.8 and 21.2 eV were used to obtain the electron spectra. From the observed differences in the electron spectra, the known characteristics of these spectroscopies, and a comparison with theory we conclude that these surfaces had small and differing amounts of impurity located principally in the selvedge or near-surface bulk rather than directly on or in the surface monolayer. The surface was cleaner than the near surface bulk. Longer heating of one sample to higher temperatures brought to the surface detectable amounts of Mo impurity that had diffused into the crystal from the Mo mounting clamps, changing the LEED pattern to √3 × √3(R 30°) and producing large modifications of both the INS and UPS spectra.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Condensed Matter Physics
- Surfaces and Interfaces