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1.
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
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The microstructure of the laser-ablated YBa2Cu3O7 (YBCO) thin film deposited on heated (100) SrTiO3 substrate was examined by transmission electron microscope. The par-ticles on the film mainly consist of CuO and few CuYO2. Most of these non-superconducting particles nucleate on or near the surface of the film and protrude about 100-400 nm in height, A large amount of a-axis YBCO grains also exist in the film, which nucleate at the substrate surface and grow perpendicularly above the c-axis YBCO film. The YBCO thin film deposited under low oxygen pressure has very different microstructure compared with YBCO thin film deposited under high oxygen pressure. 相似文献
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The photoconductivity spectra of semimagnetic semiconductor Cd0.7Mn0.3Se have been measured at 50-300 K and in the wavelength range of 5500? to 8000?. It is found that the energy gap of Cd0.7Mn0.3Se changes with the temperature linearly, and the temperature coefficient (dEg/dT) is about -7×10-4 eV/K. A photoconductivity peak which is related to Mn2+ is also found. This peak is located around 1.85 eV, nearly unshifted with variation of the temperature. The possible transition mechanisms in Cd1-xMnxSe have been discussed in the light of group theory and crystal field theory, and the results are in good agreement with experiments. 相似文献
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High quality epitaxial YBa2Cu3O7-x thin films have been succcessfully prepared by dc magnetron sputtering deposition, on (100) and (110) aligned SrTiO3, LaAlO3 and yttria-stabilized zirconia (YSZ) substrates. The films showed zero resistance around 90 K and had a Jc (at 77 K, H=0) over 106A/cm2. It was found that superconducting properties and structures of the films were strongly dependent on oxygen pressure and substrate temperature. The epitaxial structure of the films have been studied by X-ray diffraction. Rutherford backscattering and channeling spectroscopy, X-ray double-crystal diffraction and transmission election microscopy. The experimental results demonstrated that the epitaxial YBa2Cu3O7-x films had excellent superconducting properties and quite perfect structure. 相似文献
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M. Ohkubo T. Kachi T. Noritake 《Physica C: Superconductivity and its Applications》1989,160(5-6):480-488
Rutherford backscattering/channeling has been applied to study structures of as-deposited epitaxial YBa2Cu3Ox thin films prepared on {100}SrTiO3 by laser deposition. The epitaxial growth has been proved by a planar channeling experiment and transmission electron microscopy. An axial angular yield profile for barium along the c-axis has ideal characters of compensating shoulders and of a flat region at the bottom of the channeling dip. The thermal vibration amplitude, which has been determined from a half-angle of the axial angular yield profile by using Gemmell's channeling model for polyatomic crystals, is compared to those from diffraction experiments. 相似文献
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A method for determination of the oxygen content (y) in YBa2Cu3O7-y films has been established, in which the lattice conetant difference (b-a) of the films was measured and used to fit the function of (b-a) vs y for the experimental data of bulk YBaaCuaO?-y given in the literature. It is suggested that the function of (b-a) vs y can indeed be used in the case of film. In this process the twin structure of the YBa2Cu3O7-y films was used. 相似文献
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应用X射线三晶衍射对LaAlO3衬底上生长的YBa2Cu3Oy薄膜中的应力水平、存在的主要缺陷,以及薄膜与衬底的失配和取向关系等进行了研究。结果表明,薄膜在衬底上几乎完全松弛,应力很小,薄膜存在较严重的晶格取向差缺陷,这是影响薄膜晶体结构完整性的主要因素。此外,衬底与薄膜在垂直于表面和平行于表面方向都存在取向差。
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9.
A. Morimoto T. Matsuki T. Minamikawa T. Shimizu 《Physica C: Superconductivity and its Applications》1994,220(3-4):332-340
High-quality YBa2Cu3Ox superconducting thin films have been prepared on (100)MgO substrates by the laser ablation technique, and characterized by non-resonant microwave absorption (NRMA) with a field modulation, magnetization and four-probe measurements. The pinning properties derived from the NRMA spectra for various YBa2Cu3Ox films are correlated with the critical current densities Tc. A relatively high-Jc film prepared from YBa2Cu3Ox composition target using a Nd:YAG laser shows a derivative spectrum and a large hysteresis in the NRMA spectra. The highest-Jc film prepared from an YBa2Cu4Ox composition (YBa2Cu3Ox+CuO) target using an ArF excimer laser does not show a derivative NRMA spectrum, suggesting a strong pinning property. 相似文献
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R. Menegotto Costa L. Mendon?a Ferreira V. N. Vieira P. Pureur J. Schaf 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):107-113
We have studied experimentally the electrical magneto-conductivity near the
superconducting transition of YBa2Cu3O7-δ, YBa2
(Cu2.95Zn0.05)O7-δ and Y(Ba1.75Sr0.25)Cu3O7-δ polycrystalline samples. The measurements were performed in magnetic fields ranging from 0 to 400 Oe applied parallel to
the current orientation. The results show that the resistive transition of these systems proceeds in two stages. The pairing
transition occurs at the bulk critical temperature Tc, where superconductivity is stabilized within small and homogeneous regions of the
sample generically called grains. The regime of approach to the zero resistance state reveals the occurrence of a coherence
transition at a lower temperature Tc0. This transition is related to the connective nature of the granular samples and is controlled by fluctuations of the
order-parameter phase of individual grains. Our experiments show that the Zn-doping, besides depressing the pairing critical
temperature, strongly enlarges the temperature range dominated by effects related to the coherence transition. The substitution
of Ba by Sr causes only a small reduction of Tc, but also enhances significantly the effects related to the grain
coupling phenomenology. In general, our results indicate that these impurity substitutions in YBa2Cu3O7-δ produce or magnify the granularity at a microscopic level, enhancing the effects of phase fluctuations in the conductivity
near the transition. 相似文献