The possibility of applying percolation theory to the sheet resistivity of thick-film resistors, noted for the segregation of conducting particles in grain boundaries between sufficiently large particles of glass, is investigated. The experiments, carried out on model resistor films, do not satisfy the models of Malliaris and Turner and R.P. Kusy. A new model, based on the distribution of threshold concentration for two-dimensional systems of finite size, was suggested. The theoretical values of conducting pigment critical concentration in the model films studied, which are in good agreement with the experimental results, are calculated on the basis of this model.

The influence is investigated of film thickness, substrate temperature, and evaporation rate on preferred orientation and degree of crystallite order of tellurium thin films deposited in vacuum on glass substrates. Based on these dependences together with the determination of critical film thickness dependence and relative condensation coefficient on substrate temperature, the growth model of tellurium thin films is described. The preferred orientation of (hk0)‐type is found to be mainly influenced especially by the substrate temperature and deposition rate. The results are compared with those obtained by electron microscope observation of Te‐film surfaces. The results of the structure and growth investigations of Te films are supplemented by measuring some of their transport properties.

No abstract

Results are given of measurements of the temperature dependence of electrical conductivity, Hall constant, and Hall mobility of holes in Te thin films. Two series of samples with different thicknesses, prepared at two condensation rates, 1.21 and 8.60 nm/s, are measured. The temperature courses of bulk values of the hole mobility which satisfy the conception concerning the scattering of holes by barriers on grain boundaries, where the mean distance of these barriers is larger than the mean free path of holes in crystallites, are obtained by evaluating the results according to Petritz' model. It appears that the barrier height is dependent on film density.

A theory of carrier mobility in polycrystalline semiconductors which includes the influence of tunnelling through the barriers on grain boundaries is presented. The relations derived for the temperature and voltage dependence of mobility enables one to find the basic parameters of a barrier (its height and width) and of grains (the mean diameter and carrier mobility) from the experimental results. The experimental verification is carried out on tellurium films having a thickness of 3 to 10 μm, prepared by evaporation in high vacuum.