Optical second-harmonic generation and photoemission from quantum well states in thin Ag films on Si(111)

Quantization effects may occur in thin Ag films grown on a Si(I 1 1)7 x 7 s urface. In the present case such effects are studied with synchrotron radia tion 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 structureles s 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 film s showing the clearest effects are deposited at low temperature and subsequ ently slowly heated up to room temperature, (C) 2001 Elsevier Science B.V. All rights reserved.