Nanoscale variation in electric potential at oxide bicrystal and polycrystal interfaces

Scanning surface potential microscopy (SSPM), has been used to measure spat ial variations in grain boundary properties in SrTiO3 and ZnO. Experimental measurements of a Fe-doped SrTiO3 Sigma 3 bicrystal are compared to finite element calculations to quantify the effects of tip geometry and sample-ti p separation. Experimental and numerical treatments include realistic tip i nteractions and lateral inhomogeneity in sample properties. A procedure for extracting actual interface potentials from separation dependence is propo sed. Both the sign and magnitude of the grain boundary potential barrier me asured with SSPM agree with macroscopic measurements. For experimentally av ailable tips, the effect of tip geometry was found not to contribute to unc ertainty. In application to polycrystalline materials, the voltage dependen ce of individual interface properties has been determined in micropatterned , ZnO-based, polycrystalline varistor devices. (C) 2000 Elsevier Science B. V. All rights reserved.