The three-terminal devices Ag/Pb(ZrxTi1−x)O3/YBa2Cu3O7−δ(Ag/PZT/YBCO) have been fabricated onto (100) SrTiO3 by pulsed laser deposition technique and photolithography. For the purpose of application, we specially selected the PZT layer with morphotropic phase boundary composition as the gate to lower the coercive fields and decrease the operating voltage. We tried to minimize the electrode area to 6×10−6 cm2 for deeply investigating the leakage problem and getting sufficient polarization of the PZT gate, also for the high integration in future application. From the process, we obtained the following results at 64 K: the saturation polarization and the remanent polarization reach 60 and 41 μC/cm2, respectively. The coercive field is lower than 37 kV/cm, and the breakdown field is ⩾3×105 V/cm. The electric field effect measurement shows that the maximum modulation channel resistance ΔRDS/RDS is 3% under the gate voltage of ±9 V at 64 K (lower than the zero resistance temperature TC0, 70 K), at which the superconducting and normal state transition is driven by channel current IDS(IDS>Ic, Ic=15 mA).

Ultrathin (12-200 A) YBa2Cu3O7 films and [YBa7Cu3O7(l2-24A)/PrBa2Cu3O7(12-96A)} multilayers have been prepared on (100)SrTiO3 substrates with PrBa2Cu3O7 buffer layer by magnetron sputtering for dimensionality investigation of superconductivity. For developing fundamental research and application of perovskite high-T. superconductor and ferroelectric the heterostructure Pb(Zr,Ti)03/ YBa2Cu3O7 and Pb(Zr,Ti)03/Si02/Si thin films also have been prepared and investigated.Since the discovery of high-Ta perovskite superconductor, a large amount of work has been done on the mechanism of high-T. superconductivity. Ultrathin and multilayers have been considered as the ideal materials for investigation since the large anisotropic feature of high-Ta superconductors. Further, the heterostructures based. on high-Ta superconductor, ferroelectric, colossal magnetoresistance (CMR) materials, and silicon have been developed, the significance of heterostructures on developing application of high-Ta superconductor, ferroelectric, and CMR materials becomes increasingly apparent3. In this report we present the growth of ultrathin '{Ba2Cu3O7 (YBCO) films, YBa2Cu3O7IPrBa2Cu3O7(YBCOIPBCO) multilayers and heterostructures based on YBa2Cu3O7, ferroelectric Pb(ZrTi1)O3 and silicon. The investigations carried out on dimensionality of superconductivity, field effect and interface effect are also presented and discussed.1. ULTRATHIN YBa2Cu3O7 FILM AND YBa2Cu3O7/PrBa2Cu3O7 MULTILAYERS For developing YBa2Cu3O7/PrBa2Cu3O7(YBCOIPBCO) multilayers and YBCO based heterostructures the growth and investigation ofultrathin YBCO films is the key. We have developed the ultrathin YBCO films with thickness range from 24 A to 200 A. The YBCO ultrathin films were prepared by using the dc-magnetron sputtering method. The films were designed to grow on bare (100) SrTiO3 substrate (3xlOxO.5 mm) or with a 400 A-thick PrBa2Cu3O7 (PBCO) buffer layer which was deposited by the rf-magnetron sputtering method. The PBCO buffer layer may be utilized to prevent diffusion between YBCO film and SrTiO3 substrate, also a good quality PBCO layer might be beneficial for the epitaxial growth of the YBCO film. The deposition conditions were selected as follows: the sputtering gas was a mixture of Ar and 02 with a ratio of 2.5:1, the total pressure was 60 Pa; the deposition temperature was 800-820 °C. In the thickness region of 10 unit cells, with the decrease of the thickness, the film deposition temperature must be raised and have a relation of T/t -2°C /4 unit cells (t = thickness). With these conditions, the films could be synthesized reproducibly. The deposition rate was -25 A/mm for YBCO layer and -30 A/mm for PBCO layer ( We also used a gas mixture ofAr and 02 with a ratio of 3:1 and total pressure of 80 Pa, the deposition rate was almost the same for both YBCO and PBCO layers, -40 A/mm). These deposition rates were determined by dividing the thickness of the film (measured by Dektek-IIA profile meter) with deposition time. Then these deposition rates were examined by meas...