Electric Field Effect in Sm1-xCaxBa2Cu3Oy Bicrystal Junctions

A three terminal device was fabricated by depositing a thin film of Ca-doped SmBa2Cu3Oy on a bicrystal SrTiO3 substrate and then structuring a gate over the resulting junction. The channel shows RSJ-like Josephson junction behavior. By applying a voltage to the gate, a large electric field effect was observed. The largest field effect was observed in films where 30% of the Sm was replaced by Ca. The critical current of the junction was modulated 23% by the application of an electric field of 5x105 V/cm. This electric field is about 100 times smaller than the electric field necessary for the field effects observed in homogeneous films. The sign of the field effect is consistent with that expected for a carrier-depleted grain boundary region.