Complex impedance and dipolar behaviour of a silver-doped chalcogenide

Abstract

In this paper we report new measurements of the complex impedance for silver-doped samples of a-Ge₁₇Te₈₃. Measurements were made on bulk samples (both undoped and silver doped) at different temperatures and at different bias voltages over a frequency range 5 Hz-100kHz using a computer-controlled a.c. system for measuring impedance and capacitance-voltage. The impedance of the undoped sample displayed insensitivity to temperature, frequency and voltage. On doping, a drastic change in impedance parameters was observed. The resistance and capacitance of the doped sample not only increased by many orders of magnitude but also displayed great sensitivity to external stresses such as temperature and voltage. The analysis of experimental results suggests that the silver-doped Ge₁₇Te₈₃ is basically a dipolar system. The simple dipolar model that we proposed successfully explains the experimental data reported in the paper.