Optical second-harmonic generation and photoemission from quantum well states in thin Ag films on Si(1 1 1)

Quantization effects may occur in thin Ag films grown on a Si(1 1 1)7×7 surface. In the present case such effects are studied with synchrotron radiation photoemission spectroscopy and optical second-harmonic generation for a specially prepared wedge shaped film. Peaks originating from quantization perpendicular to the surface appear to dominate the otherwise structureless sp-part of the Ag valence band near the Fermi level. The second-harmonic signals oscillate with Ag film thickness with a contrast that correlates to the intensity of quantum well states observed with photoemission. The films showing the clearest effects are deposited at low temperature and subsequently slowly heated up to room temperature.