High Ferroelectricities and High Curie Temperature of BiInO_3PbTiO_3 Thin Films Deposited by RF Magnetron Sputtering Method

Properties of ferroelectric xBiInO_3-(1-x)PbTiO_3 (xBI-(1-x)PT) thin films deposited on (101) SrRuO_3/(200) Pt/(200) MgO substrates by rf magnetron sputtering method and effects of deposition conditions are investigated. The structures of the xBI-(1-x)PT films are characterized by x-ray diffraction and scanning electron microscopy. The results indicate that the thin films are grown with mainly (001) orientation. The chemical compositions of the films are analyzed by scanning electron probe and the results indicate that the loss phenomena of Pb and Bi elements depend on the pressure and temperature during the sputtering process. The sputtering parameters including target composition, substrate temperature, and gas pressure are adjusted to obtain optimum sputtering conditions. To decrease leakage currents, 2 mol% La_2O_3 is doped in the targets. The P–E hysteresis loops show that the optimized xBI-(1-x)PT (x=0.24) film has high ferroelectricities with remnant polarization 2P_\rm r=80 \muC/cm^2 and coercive electric field 2E_\rm c=300 kV/cm. The Curie temperature is about 640^\circ\!C. The results show that the films have optimum performance and will have wide applications.