YBCO／STO超导外延膜的X－射线双晶衍射研究

HIGH-Tc SUPERCONDUCTING EPITAXIAL YBa_2Cu_3O_(7-x) FILMS STUDIED BY X-RAY DOUBLE-CRYSTAL DIFFRACTION

应用Ｘ－射线双晶衍射对磁控溅射法制备的ＹＢａ_２Ｃｕ_３Ｏ_（７－ｘ）／ＳｒＴｉＯ_３超导外延膜和衬底之间的位向关系以及晶体完整性的研究，表明衬底和外延在相应的衍射面之间存在与两者点阵常数差无关的位向差。这种位向差与测量方向（φ角）有关，在孪晶界方向出现极值。外延摇摆曲线的半峰宽值显示外延完整性较差，其值与测量方向有关，而不同方向上的点阵常数变化却不大。这可能分别与孪晶存在和孪晶有择优取向以及外延镶嵌块间夹角变化有关。

The misorientation between epitaxial high-Tc superconducting film of Yba2 CuaO(7-x)(YBCO)and the substrate of SrTiO3(STO)and the crystalline perfection of the film have been studied by X-ray double-crystal diffraction. The misorientation between the film and substrate along the c-axis is not due to the lattice mismatch. It changes with φ,the angle of rotation around the normal to the film surface, and has a maximum on one of <110> directions of the substrate. The FWHMs (full widths at half maximum)of the diffracted peaks in the rocking curves of the film,indicate that the epitaxial film is not so perfect and the FWHMs change with the rotation angleφand has maximum or minimum along < 110 >.The above facts are probably due to the preferred orientation of twin boundaries and the misorientation between mosaics.