Optical properties of Mn films on dielectric substrates

Abstract

Mn discontinuous films with different mass thicknesses d (4 nm - 32 nm) were evaporated onto quartz-glass substrates under vacuum condition (p equals 10 -6 Torr). The coefficients of reflection R (from the air-side) and transmission T at normal incidence were measured in the wavelength range from 200 to 3500 nm. Using Wolter's approximation, the imaginary part of the effective dielectric permittivity (epsilon) ' 2 was determined in UV and visible. The microstructures of the films were examined with electron microscope. It has been found that optical properties of thicker, continuous films (19 nm less than or equal to d less than or equal to 32 nm) are typical as for the metallic phase, high reflection coefficient values in visible and infrared range, minimum of reflection at (lambda) equals 250 nm. In the case of thinner films (8 nm less than or equal to d less than or equal to 13 nm) maximum of reflection coefficient and imaginary part of dielectric permittivity occur in UV ((lambda) approximately equals 300 nm). These peaks may be attributed to resonance effects connected with island, discontinuous structure of the films. For the films with thicknesses d less than or equal to 6 nm maxima of R and (epsilon) ' 2 vanish and optical properties became typical as for the dielectrics, the transmission coefficients reach high values in visible and infrared range. The results of structural examinations are also presented.