Preparation And Properties Of BSCCO/YBCO Multilayer Films

High-temperature superconducting heterojunctions can be used in superconducting electronic devices,and have wide application prospect in superconducting electronic field.Bi2Sr2CaCu2O8+δ(Bi-2212)/YBa2Cu3O7-x(YBCO)high-temperature superconducting multilayer films can be prepared by Sol-Gel method.Some weak-link effect may occur at the interface of multilayer films,which can be used to superconducting micro-electronic devices.Unfortunately,there are some problems in preparation processes.Such as,property of multilayer films can be destroyed by repeatedly heat treatment.Additionally,turn superconducting heterojunctions to practical use on condition that they often need to be fine-patterned.As the limits in intrinsic characteristics of YBCO and Bi-2212,traditional fin e-pattern methods can destroy the film’s surface damage and property,and it is difficult to realize the large area preparation.Aiming at the above problems,this thesis focus on the following works:Heat treatment process of Bi-2212 films prepared by acetate based Sol-Gel method was investigated.And phase formation mechanism of Bi-2212 superconducting was discussed.Finally,Bi-2212 films grown on LaAlO3(LAO)monocrystalline substrates with c-axis epitaxial,high critical transition temperature(Tc)of 88K and critical current density(Jc)of 1.1×105A/cm2(50K,0T).Acrylic acid was used as a new photosensitive modifier to synthesis photosensitive Bi-2212 solution.The formation possibility and photosensitivity of the metal-complexes formed by metal ions and acrylic acid were researched.So,based on photosensitivity of Bi-2212 solution,fine-pattern process of Bi-2212 films was studied.Fine patterns of Bi-2212 gel films can be prepared by photosensitive Sol-Gel method,which have the smallest resolution of 3μm.Fine-pattern Bi-2212 superconducting films have c-axis growth orientation and good superconductivity.Bi-2212/YBCO and YBCO/Bi-2212 heteroepitaxial bilayer films with good extensionality have been successfully prepared on LAO substrates by Sol-Gel method.Combining the photosensitive Sol-Gel fine-pattern process,patterned structure of bilayer films was fabricated.Microstructure,superconductivity and interfacial effects of Bi-2212/YBCO bilayer films were studied.Each film in Bi-2212/YBCO and YBCO/Bi-2212 bilayer films has biaxially texture The superconducting transition steps of YBCO and Bi-2212 in the R-T curves of bilayer films were clearly observed.The first transition step has the superconducting critical transition range of 89～91K corresponding to the Tc values of YBCO film.The second transition step has the superconducting critical transition range of 80～84K corresponding to the Tc values of Bi-2212 film.Bi-2212/YBCO bilayer films have good superconductivity.Supercurrent with zero voltage occurred in I-V curves of bilayer films,the results indicated that the supercurrent mainly originated from proximity effect of SNS junctionsYBCO/Bi-2212/YBCO trilayer films with good extensionality have been prepared by Sol-Gel method.Combining the photosensitive Sol-Gel fine-pattern process,patterned structure of trilayer films was fabricated.Microstructure,superconductivity and interface effects of YBCO/Bi-2212/YBCO trilayer films were studied.Each film in YBCO/Bi-2212/YBCO trilayer films has biaxially texture.R-T curves of YBCO/Bi-2212/YBCO trilayer films showed two expected transition steps at 84～89K and 65～67K,which corresponding to the superconducting critical transition range of YBCO and Bi-2212 respectively.Supercurrent with zero voltage occurred in trylayer films.