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1.
Previously, we have reported a superheating phenomenon of a YBa2Cu3Ox (YBCO) film and studied its mechanism. In this work, we investigated the influence of microstructure on the superheating of a YBCO thin film. Different melting behaviors were observed in situ from YBCO thin films with varied microstructures by using high-temperature optical microscopy (HTOM). These films with different degrees of crystallinity were also characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). It was found that the crystalline structure features of the seed film have a great influence on the degree of superheating and the melting behavior. A high-quality film with a low fraction of interface defects is believed to be responsible for the high superheating. On the basis of the experimental results from HTOM, AFM, and XRD, the melting and superheating behaviors associated with the film defect structure are well interpreted in terms of the semi-coherent interface-energy theory. PACS 68.35.Md; 68.47.Gh; 68.55.Ac  相似文献   

2.
3 films on single-crystal MgO(100) substrates. Meanwhile, surface morphologies of as-polished and post-annealed MgO(100) substrates are investigated as well. Effects of the miscut (or misorientation) of the substrate surface on morphologies and growth mechanisms are discussed. For comparison, a typical surface morphology and growth mechanism of the spiral island structure in sputtered PrBa2Cu3O7-δ films on MgO(100) substrates are presented. Received: 27 March 1998  相似文献   

3.
蔡衍卿  姚忻  李刚 《物理学报》2006,55(2):844-848
在用YBa2Cu3Oz(YBCO)种膜液相外延生长Nd1+xBa2-xCuOz(NdBCO)厚膜的过程中,YBCO晶体在高于熔点的温度下保持不熔化并且起到了外延种子的作用.采用高温金相显微镜,我们实时观察YBCO薄膜的熔化过程,发现了超导氧化物薄膜的过热现象,并且结合XRD极图的分析和Ba-Cu-O熔体的不润湿性现象合理解释了YBCO形成过热的机制.另外,通过对具有不同微观结构的YBCO薄膜熔化行为的横向比较,研究YBCO薄膜品质对于其过热度的影响,并用半共格界面能理论很好地解释了AFM和XRD分析及实时观察熔化过程的实验结果. 关键词: 过热 YBCO薄膜 熔化形核  相似文献   

4.
3 films were produced by KrF excimer-laser ablation. Films deposited on fused silica substrates were polycrystalline without preferential orientation and had cubic rather than tetragonal structure. BaTiO3/Au/Ti/fused silica films showed a large dielectric constant, which increased with the thickness of the film, but poor ferroelectric properties. This behavior seems to be related to the small size of grains. On (100)MgO substrates oriented films were obtained. BaTiO3/YBa2Cu3O7-δ/(100)MgO films showed a large dielectric constant also and improved ferroelectric properties. Although this indicates a larger degree of tetragonality, the tetragonal structure of single crystal BaTiO3 has not yet developed. Localized reduction and metallization of BaTiO3/(100)MgO films by means of Ar+-laser radiation was demonstrated. This technique allows to produce conducting patterns in a single-s tep process. Received: 6 January 1997/Accepted: 21 April 1997  相似文献   

5.
The a-axis oriented YBa2Cu3Ox(YBCO) thin films could be grown on (100) SrTiO3(STO) substrates with STO buffer layers by dc and rf magnetron sputtering either by low-ering the deposition temperature, or by using a self-template technique. For the latter, the resistivity of the thin film at 290K along the substrate [001] direction is about four times larger than that in the [010] direction. The zero resistance temperatures Tc0 are 89 K in both directions. So high quality a-axis oriented YBCO thin films can be prepared by the self-template technique. Also the Tc0 increase monotonously with the reduction of the thickness of the YBCO seed layer.  相似文献   

6.
Tl-Ca-Ba-Cu-O epitaxial films have been successfully grown on (001) MgO substrate by liquid phase epitaxial (LPE) process. The as-grown films showed an onset of superconductivity at about 140 K and zero resistance at 111 K. X-ray diffraction analysis suggests the films to be highly preferentially oriented with the c-axis perpendicular to the film surface. Observation from transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) revealed the presence of both Tl-Ca2Ba2Cu3Oy and TlCa2Ba3Cu4Oy phases.  相似文献   

7.
We report here injection of spin-polarized carriers from a half-metallic La0.3Ca0.7MnO3 (LCMO) colossal magnetoresistive (CMR) thin film into a high-temperature superconducting YBa2Cu3O7-δ (YBCO) thin film studied using a micro-bridge. The LCMO and YBCO films were grown on 〈100〉 LaAlO3 (LAO) substrate sequentially using pulsed laser deposition (PLD). I-V measurements carried out at 77 K show that while normal critical current, I c n , of the micro-bridge is 80 mA, the critical current, I c p , through the micro-bridge when injected from the CMR layer is 38 mA. This clearly shows that spin-polarized quasiparticles injected from the the CMR layer into the YBCO layer suppress the critical current of the superconductor via the pair-breaking phenomena.  相似文献   

8.
The growth, crystal structure, and electrophysical properties of YBa2Cu3Ox (YBCO) epitaxial films grown with and without a CeO2 epitaxial sublayer on NdGaO3 (NGO) substrates with the normal to the surface deviating from the [110] axis by 5° to 26.6° around the [001] axis are investigated. It is shown that the orientation of YBCO epitaxial films grown on such substrates is determined by the existence of symmetry-equivalent directions in the substrate and in the CeO2 layer, as well as by the rate of film deposition. For a high deposition rate, YBCO films grow on the CeO2 sublayer in the [001] orientation irrespective of the orientation of the substrate and the sublayer. It was found that when the angle of deviation of the substrate plane is from the (110) NGO plane, twinning of one or both twinning complexes in YBCO may be suppressed.  相似文献   

9.
The generation of harmonics in a laser ablated YBCO film deposited on a 〈100〉 MgO substrate is reported. Higher odd harmonics appeared when the film was subjected to an ac field. The presence of a dc field induces only the second harmonic with a small value of slope ofV 2H dc curve (δV 2/δH dc) compared to bulk YBCO. The variation of the amplitude of third harmonic (V 3) withH ac and temperature was studied. These results are explained in terms of a critical state model. The observation of only a small amplitude of second harmonic (V 2) with a smallδV 2/δH dc is explained in terms of a special kind of clean grain boundary present in YBCO laser ablated films on 〈100〉 MgO.  相似文献   

10.
2 Cu3O7-δ films have been patterned by means of an arrangement employed in scanning near-field optical microscopy (SNOM). Standard SNOM probes were modified to achieve high transmission for direct writing by oxygen depletion in N2 atmosphere. The written lines are about 1.5 μm wide and show a semiconductor-like resistivity behavior (δ≥0.5). The morphology of illuminated regions is about the same as that of the YBCO films. Received: 3 July 1998/Accepted: 6 July 1998  相似文献   

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