Dielectric Relaxation and Its Effect on the Thermal Electric Characteristics of Insulators

A theoretical study is presented of the effect of dielectric relaxation on the thermal electrical characteristics of metal-insulator-metal systems in which the electrodes make blocking contacts with the insulator. The relatively simple experimental procedures indicated by the theory provide a powerful analytical method for the study of the defect nature of the insulator and the electrode-insulator interfacial barrier parameters. Basically, the theory applies to a procedure which consists of cooling the system to low temperatures, with a constant voltage $V_d$ applied. The temperature is then raised, at a constant rate of increase with time, with a constant voltage $V_i$ applied such that $V_i\ne V_d$; the current-temperature characteristic obtained during the heating is the potential source of information. It is shown that during the initial stages of the heating cycle, the conduction process is bulk limited and the electrical characteristic depicted by a non-steady-state Poole-Frenkel mechanism. At the high-temperature range of the heating cycle, a steady-state electrode-limited conducting process prevails. In the intermediate-temperature range, pronounced thermally stimulated dielectric-relaxation currents (DRC) are predicted to occur. These currents exhibit pronounced maxima, and the temperatures at which they occur are related to the energies of trapping levels in the insulator and to the heights of the interfacial barriers. The area under the DRC curves is directly proportional to the charge removed from, or supplied to, the traps; a quantitative knowledge of this charge exchange permits an estimation of the trap density in the insulator.