Electrical characterization of ZnO multilayer varistors on the nanometre scale with conductive atomic force microscopy

The conductivity of ZnO–varistor ceramics has been analyzed with conductive atomic force microscopy (C-AFM) under atmospheric conditions by measuring the current at different voltages and positions in zinc oxide-based multilayer varistors (MLVs). It is possible to detect individual ZnO grains on the polished sample surface in the AFM topography mode as well as in the two-dimensional current images. Additionally local current–voltage (IV) curves revealed details of the electrical behaviour of the material. To correlate the laterally resolved current image with grain orientations, electron backscattering diffraction (EBSD) has been performed. Beside the well-known varistor behaviour specific influence of the local microstructure has been found.