ASYMMETRIC FERROELECTRICITY AND ANOMALOUS CURRENT CONDUCTION IN HETEROEPITAXIAL BATIO3 THIN-FILMS

Asymmetric ferroelectricity and conduction of anomalous leakage curren t were observed in heteroepitaxial BaTiO3 thin films grown by rf magne tron sputtering at 600 degrees C on three different electrode/substrat e combinations: SrRuO3/SrTiO3, Pt/MgO and Nb doped SrTiO3. The voltage shift of hysteresis loops of the capacitance was a linear function of the thickness of the BaTiO3 films and became as large as 10 V in the him with a thickness of 410 nm. The asymmetry did not disappear even a fter a heat treatment carried out at 800 degrees C in air. On the othe r hand, a steep increase in the leakage current was observed in the he teroepitaxial films when a positive voltage was applied. The origin of both the asymmetric hysteresis and the anomalous conduction is discus sed in terms of asymmetric crystal structure caused by misfit dislocat ions introduced in heteroepitaxial growth.