Photoelectron intensity oscillation as a probe to monitor Si layer-by-layer growth

Photoelectron intensities from the surface state on Si(100)2 × 1 periodically oscillate during Si epitaxial growth, for which an alternation between 2 × 1 and 1 × 2 surface reconstructions has been proposed as an origin [Y. Enta et al., Surf. Sci. 313 (1994) L797]. To confirm the scheme more directly, we have performed synchrotron radiation ultraviolet photoelectron spectroscopy (UPS) measurements on both 2 × 1 and 1 × 2 surfaces. As a result, an apparent difference between the two valence-band spectra was observed, whose difference spectrum presented a good agreement with the dependence of the oscillation amplitude on the photoelectron energy, proving the validity of our previous proposal. A selection rule argument on the initial and final state symmetries yields an insight on the origin for the oscillation. With its very high sensitivity, UPS oscillation can be a powerful tool for monitoring the layer-by-layer growth at surfaces.