ELECTRICAL SWITCHING OF 2-PHASE ZNO-PRC0O3 THRESHOLD SWITCHING MATERIALS

Electrical switching of ZnOPr6O11Co3O4 ceramics was investigated. The roles of individual grains and interphase boundaries in the electrical switching behavior of bulk two-phase threshold switching material based on ZnOPr6O11Co3O4 were studied using microelectrodes deposited photolithographically on a thin section of the material. The materials consists of Co-doped ZnO and Zn-doped PrCoO3 phases. Pristine Co-doped ZnO grains showed high "off" state resistance and a high threshold switching voltage for the initial voltage sweep and were permanently conductive for subsequent sweeps. "Damage traces" were observed in these grains after initial switching. Zn-doped PrCoO3 grains exhibited stable and reproducible threshold switching behavior. Through the study of the electrical characteristics of single-phase polycrystalline undoped and Co-doped ZnO materials and undoped and Zn-doped PrCoO3 materials, the microelectrode observations of the switching behavior of the two-phase material were confirmed. Undoped ZnO showed n-type semiconductivity with a resistivity of around 1 Ω-cm. Doping ZnO with Co increased this resistivity. Evidence was obtained that the resistivity increase in ZnO accompanying doping with Co was not due to blocking contacts. Undoped and Zn-doped PrCoO3 showed p-type semiconductivity with a resistivity of around 100 Ω-cm. Doping PrCoO3 with Zn decreased the resistivity. A blocking contact was observed between PrCoO3 and electrode metals having low work function. A microstructural model of the switching behavior of two-phase ZnOPrCoO3 material is proposed on the basis of this study. © 1991.