Preparation of zinc oxide metal oxide multilayered thin films for low-voltage varistors

Zinc oxide/metal oxide multilayered composite thin film varistors have been fabricated by the radio-frequency (RF, 13.56 MHz) sputtering method and th e electrical properties of the films were investigated. After the Au electr ode was formed on a quartz substrate by vacuum evaporation, zinc oxide (ZnO ) layer was deposited by the RF sputtering with ZnO target at room temperat ure, Ar partial pressure of 2.5 Pa, O-2 partial pressure of 2.5 Pa and RF p ower of 50 W. Praseodymium oxide (Pr6O11) layer was formed on the ZnO layer by the RF sputtering with Pr6O11 target at room temperature, Ar pressure o f 5 Pa and RF power of 80 W. The upper Au electrode was formed on the Pr6O1 1 layer by vacuum evaporation. The conduction mechanism of the ZnO/Pr6O11 d ouble-layered thin film varistor was discussed on the basis of the measurem ents of voltage-current (V-I) and capacitance-voltage (C-V) characteristics and thermally stimulated current (TSC). From the results of V-I and C-V me asurements, if was found that a depletion region was formed in the ZnO laye r close to the interface between ZnO and Pr6O11 layers. (C) 1998 Elsevier S cience Ltd. AII rights reserved.