Optical response of Pb quantum wells on Si(111)-(6×6)-Au

Ultrathin Pb films deposited on Si(111)-(6×6)-Au at 105 K in ultrahigh vacuum (UHV) conditions were studied by means of differential reflectance (DR) spectroscopy. The optical signal from spectral range 0.25-0.60 eV has been measured in situ during Pb film growth. Base on DR data the imaginary part of the Pb dielectric function, the optical conductivity and the plasma frequency were determined. The scattering time of the electrons involved in optical transitions was obtained according to the Keller and Liu local field theory [O. Keller, A. Liu, Phys. Rev. B 49 (1994) 2072].