THERMIONIC, TUNNELING, AND POLARIZATION CURRENTS IN ZINC-OXIDE VARISTORS

We report an analysis of time, voltage, and temperature dependencies f or ZnO varistors conductance. The conduction mechanisms proposed to in terpret experiments include thermionic, tunnelling, and polarization c urrents. We analyse here the contributions of these mechanisms to cond uction in order to identify their roles. We conclude that a tunnelling current shows the correct trends in the current-temperature curve. Al so, capacitance measurements as a function of time and temperature are presented to discuss the influence of interface and deep bulk traps. (C) 1997 Elsevier Science Limited.