Electronic characterization of single grain boundary in ZnO : Pr varistors

Isothermal capacitance transient spectroscopy (ICTS) has been applied to st udy single grain boundaries of ZnO:Pr varistors using micro-electrodes prep ared on the surface of the ZnO ceramic. A similar ICTS peak was observed as in the case of bulk measurement. This peak has directly proved the existen ce of the electronic interface states and formation of double Schottky barr ier (DSB) at the grain boundary. The quantitative analysis of ICTS peak hei ght revealed that the higher density of the interface states gave the highe r nonlinearity of a I-V relation. Photo-ICTS spectra were also examined for the single grain boundary. The peaks shifted to shorter time compared with the dark-ICTS spectrum when the irradiated light brought about an increase of the junction capacitance. This result gave detailed information about d eep electronic interface states of DSB. (C) 2000 Elsevier Science Ltd and T echna S.r.l. All rights reserved.