Surface potential at surface-interface junctions in SrTiO3 bicrystals

An analytical approach to the quantification of electrostatic force microsc opy and scanning surface potential microscopy images of systems with electr ic potential inhomogeneity has been developed in order to determine the int erface potential in a donor-doped Sigma5 SrTiO3 grain boundary. The voltage dependencies of the electrostatic force gradient and surface potential ver ify the solutions. The distance dependencies of force gradient and surface potential were used to quantify the potential at the grain boundary-surface junction and the depletion width. Both measurements yield the same propert ies despite the difference in imaging mechanisms. The interface potential i s shown to result from local charge rather than from a local variation in d ielectric constant. The amount of charge implied by an interface potential of 30 mV would render detection of associated defects impossible, but these results represent a lower limit in intrinsic bulk grain boundary potential .