MEASUREMENT OF SPACE-CHARGE ADJACENT TO OXIDE GRAIN-BOUNDARIES BY TUNNELING SPECTROSCOPY

The electrical properties of grain boundaries in polycrystalline oxides are characterized by STM imaging and tunneling spectroscopy. The use of tunneling spectroscopy to distinguish grain boundaries from other surface features is discussed. In the case of SrTiO3, spatial variations in electronic structure indicate the presence of space-charge regions adjacent to the grain boundaries. The sign of the interface charge and the local charge carrier concentration variations can be deduced from the tunneling spectra.