Fabrication of single boundary electroceramic devices controlled by localized quantum structure at boundaries

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In most of electroceramic materials, double Schottky barriers formed at grain boundaries are often used to obtain unique electrical properties. For example, practical devices such as positive temperature coefficient of resistivity (PTCR) devices and varistic one use the electrical properties given by double Schottky barriers (DSB). In general, the electrical properties of DSB are formed by electrons trapped at interface states at grain boundaries. So, to understand and to develop high quality devices, it is necessary to clarify an origin of the interface state by systematic investigation using single boundary phenomena, for example, well-defiled samples such as bicrystals. This study aimed to reveal relationships between grain boundary atomic structure and its electrical properties, and further, to fabricate devices with single grain boundary. Nb-doped SrTiO3 and ZnO were used for materials. In a range of small tilt angles, all of the boundaries are consisting of grain boundary dislocations. In addition, non-linearity observed in current-voltage property at such grain boundaries was found to show a tilt angle dependency. Namely, a height of DSB is closely related to a density of grain boundary dislocations. By detail investigation, non-linearity becomes largest at about 10degress boundary. This may be because that boundary has a special array of grain boundary dislocations. Meanwhile, in ZnO bicrystals, large non-linearity could be obtained in Pr-doped ZnO bicrystals without any amorphous phases.