Dielectric properties of thin films of chalcogenide glasses

Abstract

The temperature-frequency dependences of the conductivity (σ), capacitance (C), and dielectric-loss coefficient (e″) have been measured for metalglass film (composition As30Ge10Si12Te48)-metal structures in an alternating electric field. The glass film was obtained by the method of radiofrequency sputtering in an argon atmosphere, and the top and bottom molybdenum electrodes by thermal evaporation in vacuum. The measurements were made in the frequency range 4·102−2·104 Hz at temperatures 209–299°K. The relaxation component σr=σ∼−σ− of the conductivity for T < 240°K and high frequencies does not depend on the temperature (T) and is proportional to ω0.8. At higher temperatures, σr(ω) is described by a complicated curve, which has at low frequencies the behavior ≈ω2 and goes over to saturation at large values of ω. In this range of frequencies and for positive temperatures σr ≈ exp(ΔE/ϰT), where ΔE ≈ 0.45 eV. The frequency-temperature dependences of σr, C, and e′' are interpreted on the basis of Frohlich's model. The calculated and experimental curves are compared. It is assumed that the loss of relaxation type is due to two processes, one of which is governed by carrier hops between localized states near the Fermi level and is predominant at low temperatures. The other is determined by carrier hops between the same states through the valence band and is predominant at positive temperatures.