Deposition And Characterizations Of Ferroelectric/Superconducting Thin Film Heterostructures

Recently, perovskite oxides have attracted considerable attention in many fields due to their fruitful chemical and physical properties, such as ferroelectricity, ferromagnetism, piezoelectricity and superconductivity, etc. These various properties have provided a broad space for fundamental physics research. Besides that, perovskite oxide heterostructures have provided additional degrees of freedom for performance characterizations.This work optimized the preparation of the YBa2Cu3O7-δ (YBCO), Pb(ZrxTi1-x)O3 (PZT), Lao.7Sro.3Mn03 (LSMO) film by pulsed laser deposition. High quality YBCO/PZT/LSMO heterostructure was obtained on SrTiO3 (STO) substrate. Characterization the structure and properties of the heterostructure and studying the ferroelectric control on high temperature superconductivity transport properties. Meanwhile we explored the preparation of ferroelectric thin film (Ca,Sr)3Ti2O7. Major achievements are summarized below.(1) Pb(Zr0.52Ti0.48)O3/LSMO, YBCO thin films with smooth surface were deposited on SrTiO3 subsrates. X-ray diffraction indicates that the Pb(Zro.52Tio.48)03 and YBCO thin film have well crystallinity. Piezoresponse force microscopy measurements show that PZT can be written into two domains with 180 degrees phase contrast and clear domain boundaries can be observed. The low temperature R-T crave of YBCO show the emergence of superconductivity, with 84 K transition temperture and 12 K transiton temperature range. PZT thin film is a single domain, the polarization direction perpendicular to the film surface. By controlling the parameters of deposition, we obtained the opposite direction of spontaneous polarization in different ingredient PZT films. The spontaneous polarization direction of Pb (Zr0.52Ti0.48)03 is turn to the surface of thin film. The spontaneous polarization direction of Pb(Zr0.1Ti0.9)03 is turn to substrate.(2) Comparison the transport properties of YBCO on two heterostructures structure of YBCO/Pb(Zr0.52Tio.48)03/LSMO and YBCO/Pb(Zr0.iTi0.9)03/LSMO, it is observed that the effect of different initial spontaneous polarization on YBCO superconducting transiton properties which were acheieved nearly 9 K change. Furthermore, by the micromachining of YBa2Cu3O7-δ/Pb(Zr0.52Ti0.48)O3/ Lao.7Sro.3Mn03/SrTi03 heterostructures, we obtained the FET structure with 500 μm wide YBCO strip. Applying an external electric field to polarize PZT, it is observed that that PZT polarization reversal will change superconducting transition temperature of YBCO which were acheieved nearly 10 K change. This shows that the polarization of PZT have characterizations on YBCO superconducting transport properties.(3) The fabrication of (Ca,Sr)3Ti2O7 ferroelectric thin films, we prepared target of (Ca,Sr)3Ti2O7 by solid phase sintering. A series of (Ca,Sr)3Ti2Oy ferroelectric thin films were fabrication on the SrTiO3 and LaAl03 subsrates. The films show smoth surface. X-ray diffraction indicates that thin film have well crystallinity.