Scanning tunneling microscopy is an innovative new method of surface atomic and electronic structural analysis with subatomic spatial resolution. Structural imaging and current image spectroscopy with STM will be used to investigate the effects of dopants on the electronic structure of ZnO varistor materials. The electronic structure in the depletion lasers near the grain boundaries will be compared with that in the center of the grains. The structure of the grain boundary will be probed to determine if grain boundary trapping states are due to segregated impurities or lattice strain defects. These results will be compared to existing models of varistor behavior. The impact of this work will be seen in two fields. As the first demonstration of scanning tunneling microscopy in ceramics it will illustrate an expanded potential of the techniques and be the basis of further work in this area. The characterization of ZnO electronic structure will be useful in refining models of varistor behavior and guiding future composition modifications.
