Electric field effect on the artificial grain boundary of bicrystal YBa2Cu3O7−δ films

An ability of the artificial grain boundary of bicrystal YBa2Cu3O7−δ thin films is demonstrated as the field effect channel of high Tc field effect devices. The influence of field application on the channel resistance is examined with a metal-insulator-semiconductor-type structure, in which a channel is arranged across the grain boundary. The field-induced change in the resistance of the grain boundary is enhanced up to around 5% by lowering temperature below Tc of adjoining YBa2Cu3O7−δ grains. The enhancement is explained not only by an increase in the dielectric constant of the gate insulator (SrTiO3) but also by a reduction in the carrier density nearby the grain boundary. The latter is indeed a benefit to high Tc field effect devices.