Fabrication, characterization, and properties of neodymium(2-x) cesium(x) copper oxygen(4-y) superconducting thin films and heterostructures

Fabrication, characterization, and physical properties of electron-doped {dollar}rm Ndsb{lcub}2-x{rcub}Cesb{lcub}x{rcub}CuOsb{lcub}4-y{rcub}{dollar} superconducting films and heterostructures are systematically explored in this work. {dollar}rm Ndsb{lcub}2-x{rcub}Cesb{lcub}x{rcub}CuOsb{lcub}4-y{rcub}{dollar} (NCCO) thin films, with a T{dollar}sb{lcub}rm c{rcub}{dollar} of 22.4K and a {dollar}rm Deltasb{lcub}c{rcub}{dollar} of 0.2K were fabricated by pulsed-laser deposition using N{dollar}sb2{dollar}O reactive gas. The films are c-axis oriented, epitaxially grown with a small mosaic spread of 0.2{dollar}spcirc{dollar} and an RBS channeling yield of {dollar}sim{dollar}10%. Cross-sectional TEM images reveal that the films do not contain any polytypoidic faulting and the interface between NCCO and substrates is sharp. Fluorite-type YSZ has been found to be the most-suited substrate for the growth of NCCO films among the substrates studied. The results also suggest a strong correlation between the strain and T{dollar}sb{lcub}rm c{rcub}{dollar} in NCCO thin films. Properties of NCCO as a function of oxygen and/or Ce doping were studied by the proper post-treatment of NCCO films in vacuum and/or oxygen atmosphere. The in-plane transport properties indicate that both holes and electrons contribute to the charge transport in the superconducting phase of NCCO. The temperature dependence of the in-plane penetration depth {dollar}lambda{dollar}(T) and surface resistance R{dollar}sb5{dollar}(T) can be described well within the s-wave BCS framework over the entire temperature range below T{dollar}sb{lcub}rm c{rcub}{dollar} and this behavior is found to be insensitive to the disorder in the film.; Bilayer heterostructures of c-axis {dollar}rm YBasb2Cusb3Osb7{dollar} (YBCO)/NCCO in which both layers were superconducting, with transition temperatures(T{dollar}sb{lcub}rm co{rcub}){dollar} of 88.5 K for YBCO and 18.5 K for NCCO were fabricated for the first time by in-situ pulsed laser deposition. The conflicting material processing requirements, oxygenation for YBCO and reduction for NCCO in the same sample were solved by using N{dollar}sb2{dollar}O reactive gas with a specific cooling procedure in an oxygen ambient. Josephson supercurrent was observed across the interface of the YBCO and NCCO superconducting layers, confirmed by flux quantization experiment in a YBCO/NCCO loop, indicating phase coherence between YBCO and NCCO. The systematic studies on different device structures imply that the observed supercurrent between YBCO and NCCO cuprates is along c direction, which is not consistent with the idea of pure s-wave pairing in NCCO and pure d-wave pairing in YBCO.