Abstract
The local electronic properties of individual grain boundaries of SrTiO3 bicrystals and ZnO based varistor polycrystals have been determined via scanning surface potential microscopy (SSPM). This technique employs a conducting AFM tip as a Kelvin probe to map surface potentials, providing a direct measurement of the potential barrier of SrTiO3 bicrystals and therefore the sign of the interface charge. Two-dimensional finite element simulations are used to characterize the distance dependence of the tip-sample interaction, allowing potentials at the surface to be determined from measurements above the surface. By performing SSPM during in situ sample biasing through microfabricated contacts, the voltage dependence of the barrier height, interface charge, and ultimately the energy dependence of the interface density of states can also be locally obtained. Positional variations of each of these properties have been quantified along individual interfaces.