P. Biegański

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

Photovoltaic properties of ZnO nanorods/p-type Si heterojunction structures

Summary Selected properties of photovoltaic (PV) structures based on n-type zinc oxide nanorods grown by a low temperature hydrothermal method on p-type silicon substrates (100) are investigated. PV structures were covered with thin films of Al doped ZnO grown by atomic layer deposition acting as transparent electrodes. The investigated PV structures differ in terms of the shapes and densities of their nanorods. The best response is observed for the structure containing closely-spaced nanorods, which show light conversion efficiency of 3.6%.

Determination of non-homogeneity in Vycor glasses by means of positron annihilation and analysis of electron microscope images

Abstract The paper presents results of measurements of heterogeneity of Vycor-type glasses, which contain pores. Concentrations and sizes of the pores affect glass quality and transmission of light. Lifetime parameters of positron annihilation in the samples have been measured. The same material was next investigated by means of electron microscopy to observe pores and measure their sizes. Comparison of the two measurements was then made; a correlation between the average lifetime for the long-life component, τ2 (as obtained from the annihilation measurement), and average cavity radii (as obtained from the analysis of electron microscope images) was found.

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.