The interference modulated transmission spectra T( lambda ) at normal incidence for amorphous arsenic sulphide semiconducting films deposited by thermal evaporation were obtained in the spectral region from 300 nm up to 2000 nm. The straightforward analysis proposed by Swanepoel (1983), which is based on the use of the extremes of the interference fringes, has been applied in order to derive the real and imaginary parts of the complex index of refraction and also the film thickness. Thickness measurements made by a surface profiling stylus have also been carried out to cross check the results obtained by the method employing only T( lambda ). In addition, the optical band gap Egopt has been determined from the absorption coefficient values using Tauc's procedure, i.e. from the relationship alpha (h nu )=K(h nu -Egopt)2/h nu , where K is a constant. Finally, it is emphasised that accurate results were achieved not only with the above mentioned glass composition As2S3, but also in the case of the non-stoichiometric composition As30S70.

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An expression relating the resistivity, R, of a segregated system of conducting and non-conducting media to the volume fraction, V, of the conducting component has been derived by applying percolation theory to a simple but realistic model of the system microstructure. It is proposed that R varies as (p'-pc)- mu where pc is the percolation threshold, mu is the conductivity critical exponent for 3D systems and p' is the fraction of sites in the conducting region that are filled by conducting particles; p' is related to V. The expression can be used to fit the observed R-V curves (blending curves) of thick film resistor systems, which are known to have a segregated structure. The model is valid over a useful range of volume fractions and employs typical values for pc and mu .

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The pressure induced phase transition in s-triazine has been studied using Raman scattering. Some of the features observed in a previous Raman scattering study of the phase transition at atmospheric pressure have also been observed in the present case, and a preliminary analysis based on an estimated form of the pressure dependence of the order parameter is reported. However, the data presented in the present study can not yet be fully reconciled with the corresponding results at atmospheric pressure. It is suggested that some of the different theoretical ideas concerning the transition developed for atmospheric pressure and variable temperature could be applied in the analysis of the effects of pressure. No additional phases of s-triazine were observed at pressures up to about 30 kbar within the temperature range 15–295 K.