Infrared spectroscopy of Pb layer growth on Si(111)

The growth of Pb films on Si(111)-(6×6) Au and on Si(111)-(7×7) Au at 1200.3em0exK was investigated in situ with infrared transmittance spectroscopy. In the development of the transmission spectra with film thickness the formation of the crystalline layer, the layer-by-layer growth mode, and size effects can be identified. The infrared spectra are analyzed with the Drude model for the dielectric function. In order to get a good fit, both the parameters' plasma frequency and relaxation rate must become thickness dependent, which is explained in relation to the quantum-size effects and to the classical-size effect. This work is the first infrared spectroscopic study of quantum-size effect-related oscillations in metal films.