The Pt films with mass thicknesses ranging from 0.8 to 4.7 nm were evaporated onto quartz-glass substrates under vacuum conditions (p~10-4 Pa) with evaporation rate ~0.01÷0.2 nm/s. Transmittance spectra were measured in the wavelength range from 196 to 2500 nm. The microstructures were examined by electron microscope. The films with low coverage coefficient consist of islands regular in shape, they prevail in the structure. With coverage coefficient increase the islands become more irregular and join one with other. The experimental and calculated histogram are presented. It has been found that for the films examined the dependencies of transmittance on wavelength exhibit the minima which shift to longer wavelengths with coverage coefficient increase. These optical properties are typical for the island films. The structural examinations confirm island structures of the films examined.
On the basis of the previous structural and electrical examinations it has been found that thin, especially discontinuous Mn films even under vacuum conditions are quickly oxidized. In order to protect from this process just after evaporation of Mn films, its were in vacuo covered with MgF2 layers. The influence of MgF2 dielectric layers with thickness dd approximately equals 21 nm on the optical properties of Mn films was investigated. The thicknesses of Mn films varied from 4 to 32 nm. Optical properties of double films (Mn + MgF2) differ distinctly from those of single Mn-films. Dielectric layers with thickness dd approximately equals 21 nm protect from oxidation process and cause an increase of reflection coefficients and decrease of transmission coefficients in the visible and infrared range.
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.
Fractal structures have been observed in discontinuous Mn films evaporated onto quartz-glass substrates in vacuo (10-8 Torr). The microstructures of the films were examined with high resolution electron microscope. On the basis of the micrographs, the coverage coefficients were determined for the Mn films. The fractal dimensions of Mn films were determined using the box-counting by squares method. It has been found that the fractal dimensions D depends on the film structure characterized by coverage coefficient p. In the considered coverage coefficient range the fractal dimension increases with increasing p, approaching D equals 2 for continuous films.
Mn discontinuous films with different thicknesses d were evaporated onto quartz-glass substrates at different temperatures under vacuum conditions (p equals 10-8 Torr). The microstructures and crystallographic orientations were examined with high resolution electron microscope. On the basis of the diffraction patterns the contents of islands and their influence on the electrical properties were determined. The temperature dependencies of resistance R(T) were measured in vacuo in situ for the Mn films with different thicknesses. Making use of the measured data the activation energies of resistance E were calculated for the films with different thicknesses and for the films obtained under different evaporation conditions.
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