QUANTUM-SIZE EFFECTS IN THE OPTICAL CONDUCTIVITY OF ULTRATHIN METAL-FILMS

Optical and electrical properties of ultrathin (0.15-7 nm) metal films (Nb, Cu, Mo, W, Ni and Ti) deposited by radio-frequency sputtering ha ve been studied. Infrared (IR) reflectivity, transmittance as well as direct current (DC) conductivity measurements have been used to charac terise these films The periodic thickness dependence of the optical an d DC conductivity was found. The periods of oscillations for different metals are of the order of the electron Fermi wavelength. Thus it was proposed that these oscillations are due to quantum size effects.