E. Dobierzewska-Mozrzymas

Optical properties of granular aluminum films.

The optical properties and microstructure of island aluminum films evaporated onto NaCl substrates were investigated. Using Wolters approximation, the imaginary part of the effective dielectric constant of both UV and visible ranges was determined. The resonance peak ∊2′ was found to occur in both the UV and visible. The experimental results are discussed in terms of a modified Maxwell-Garnett theory.

Optical properties of discontinuous copper films

The optical properties of discontinuous copper films on quartz substrates at volume fractions ranging from 0.19 to 1.0 are investigated. The range of dielectric properties, the percolation threshold, and the range of metallic properties are determined. The transmittance spectra of copper films with low volume fractions are interpreted in terms of a modified Maxwell-Garnett theory.

Conduction Mechanisms in Discontinuous Pt Films

Electrical properties of discontinuous Pt films were investigated. Pt films with different coverage coefficients (p) were evaporated onto quartz-glass substrates under vacuum conditions (p 10 -4 Pa). The temperature dependencies of resistance measured in vacuo in situ made possible to determine the activation energy of resistance for the films. These values of activation energy were compared with those obtained on the basis of structural examinations conducted by means of electron microscope. The dependencies of the island diameters and of the gaps on coverage coefficient were determined for examined films. The log of resistance of Pt films versus coverage coefficient was also presented. It has been found that the electrical properties of the film are subject to change near the percolation threshold. This behaviour is attributed to a change in the type of conduction. Films with coverage coefficient p p C the resistances reach lower values, the activation energies of resistance are near to zero. The conduction mechanisms in discontinuous Pt films are proposed.

Optical properties of gold and aluminum island films with regard to grain size and interisland spacing distributions

In this study, optical properties of gold and aluminum island films are described in terms of a classical macroscopic model. The distributions of island diameters and interisland spacing are assumed to be lognormal. The study also involves the effective permittivity of the surrounding. There is good agreement between theoretical and experimental results, especially for small-thickness and small-grain-size films.

Fractal dimension of discontinuous copper films

Fractal-like structures have been observed in discontinuous Cu films evaporated onto quartz substrates in vacuo (10 −9 torr). The microstructures of the films were examined with an electron microscope using a carbon replica. On the basis of the micrographs, the coverage coefficients and the distributions of the island sizes and gap sizes were determined for the Cu films with the coverage coefficient (p) ranging from 0.3 to 1. The discontinuous films were also simulated by computer for 0.1 < p < 1. The fractal dimensions of the evaporated and modelled films were determined using the box-counting method. It has been found that the fractal dimensions (D) depend on the film structure characterized by the coverage coefficient. In the coverage coefficient range considered the fractal dimension increases with increasing p from D = 1.74 to D = 2, approaching value D c = 1.84 in a percolation threshold. The experimental values are in good agreement with the computer simulations

Application of a computer model for determining the contribution of the fundamental conduction mechanisms in discontinuous metal films—Aluminium on NaCl

Abstract A computer model is developed that enables resistance calculations for a discontinuous film on a dielectric substrate. The advantage of the model is the inclusion of such mechanisms as metal conduction, substrate conduction, tunnelling and thermally activated tunnelling. The computer-modelled film structure is equivalent to a real structure determined by microscopic examinations. The resistance is calculated in terms of a specific algorithm. Making use of the computer method, the temperature dependence of the resistance as well as the relationship between log(resistance) and coverage coefficient for discontinuous aluminium films on NaCl are calculated. The agreement between calculated and measured data is good.

Optical properties of copper island films with consideration of grain size and interisland spacing distribution

Optical properties of discontinuous Cu films were investigated in UV, in the visible range and in the near IR. It was found that the plot of the transmission coefficient in IR differed according to the volume fraction of the film. Optical anomalies were explained in terms of the modified Maxwell-Garnett theory.

Electrical properties of island aluminium films evaporated onto an NaCl substrate

Abstract Aluminium films with an island structure were evaporated onto an NaCl substrate under conditions of ultrahigh vacuum (10 -9 Torr) and their electrical properties were examined. The temperature dependence of the film resistance in the range 100–400 °C was measured in vacuum in situ . Ohmic characteristics of the films were plotted for selected temperatures. The microstructure and crystallographic orientation were determined.

The fractal structure of discontinuous metal films: copper films on glass substrates

Abstract Fractal structures were observed in discontinuous Cu films evaporated onto quartz-glass substrates in vacuo (10−8 Torr). On the basis of electron micrographs, the coverage coefficients, fractal dimensions D and correlation lengths ξ were determined for the Cu films with coverage coefficients p ranging from 0.3 to 1. The correlation function method was used to determine the fractal dimensions for the experimental, as well as for the computer modelled films. In the percolation range some critical exponents (β, ν) were determined. The results were compared with the values theoretically predicted, and with the results previously obtained.

Lévy's distributions for statistical description of fractal structures; discontinuous metal films on dielectric substrates

Abstract The ranges of statistical description of the systems may be determined on the basis of the inverse power law of the Mandelbrot. The slope of the straight line representing the power law in a double-logarithmic plot, determined as −1/μ (μ being a critical exponent), characterizes the distribution of elements in the system. In this paper, the inverse power law is used to describe the statistical distribution of discontinuous metal films with higher coverage coefficients (near percolation threshold). For these films the critical exponent μ≈1, both the mean value and the variance are infinite. The objects with such microstructure are described according to the Levy distribution; Cauchy, inverse Gauss and inverse gamma distribution, respectively. The experimental histograms are compared with the calculated ones. Inhomogeneous metal films were obtained experimentally, their microstructures were examined by means of electron microscope. On the basis of electron micrographs, the fractal dimensions were determined for the metal films with coverage coefficient ranging from 0.35 to 1.00.