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1.
SURFACE PHASE DECOMPOSITION IN Bi2Sr2CaCu2O7-y SINGLE CRYSTALS UNDER NITROGEN IONS IRRADIATION 下载免费PDF全文
The influence of irradiation by 30 keV nitrogen ions with a fluence 1×1018N+·cm-2 on the crystal structure of single crystal Bi2Sr2CaCu2O7-y was investigated by means of X-ray photoelectron spectroscopy and X-ray diffraction. The irradiation caused a transformation from Bi2Sr2CaCu2O7-y (2212 phase) to Bi2Sr2CuO5-x (2201 phase). It was observed that. a small amount of metallic bismuth with an average thickness of about 6.3nm appeared after the irradiation. The possible reaction mechanism under nitrogen-ion irradiation was discussed. 相似文献
2.
使用牛津震动样品磁强计(VSM)研究了Bi2Sr2CaCu2O8单晶的磁滞回线.在20到40K温度之间发现了反常的尖锋效应,随样品O含量的增加,发生尖锋效应的外场也相应提高.可以认为在尖峰效应处发生了由涡漩物质的有序固态到无序固态的相变,在有少量点缺陷存在的BSCCO单晶相图上,Bsp线终止于20K温度处,在20K以下温区没有发生准格子到涡漩玻璃的相变,涡漩固相始终以准格子形式存在;可以认为尖峰效
关键词:
2Sr2CaCu2O8单晶')" href="#">Bi2Sr2CaCu2O8单晶
磁滞回线
尖锋效应
相变 相似文献
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本文研究了Bi-Sr-Ca-Cu-O体系中理想成份为Bi2Sr2CaCu2O8化合物的超导性能和晶体结构。名义成份为BiSrCaCu2O5.5零电阻超导转变温度Tc(0)=81.5K。用X射线粉末衍射方法测定了Bi2Sr2CaCu2O8的晶体结构,其基本结构属体心四方晶系,空间群为D4h17-l4/mmm,点阵常数a=3.825?,c=30.82?。每单胞化合式单位为2.2Ca占据2(a)等效点系,4Sr,4Bi和4Cu占据三组4(e)位置,其原子参数z分别为0.110,0.302和0.445,16O分别占据8(g),z=0.445和二组4(e),z=0.210和0.380。Bi2Sr2CaCu2O8晶体结构可认为是阳离子沿z轴的(00z)和((1/2)(1/2)z)交错排列,由Aurivillius相导生出来的。讨论了在Bi-Sr-Ca-Cu-O体系中可能存在的其它沿z轴不同堆垛层数的超导相。
关键词: 相似文献
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对高品质单相多晶Bi2Sr2CaCu2O8+δ样品作真空或H2气氛中不同温度下的热处理。由X射线结构分析,其正常态和超导态性质(特别是载流子浓度)的系统测量结果表明:Bi2Sr2CaCu208+δ样品在H2气氛中热处理,其氧的释放可分为两个阶段:一是Bi-O层之间的过量氧原子的逸出,降低系统的载流子浓度,从而调节Tc;二是CuO2面内氧原子的迁移,产生氧空位,使CuO2面内Cu2+的短程二维反铁磁(2D-AFM)有序背景遭到破坏。可以认为:以往文献中报道的Bi2Sr2CaCu2O8+δ超导体的吸氢效应导致Tc的变化,很可能主要的并不是氢原子的电子掺杂行为,而是与吸氢过程中氧含量的变化相联系。
关键词: 相似文献
11.
X.F. Hu 《Surface science》2006,600(11):2252-2257
Temperature dependent infrared study of water adsorption on the bc-plane of a Bi2Sr2CaCu2O8 (Bi2212) single crystal reveals that water is molecularly physisorbed, and forms hydrogen-bonded clusters in the temperature range of 85-150 K. Although dissociative adsorption is expected on surfaces terminated with Ca-O and Cu-O groups, no dissociated species is detected. The main absorption bands occur between 3200 and 3500 cm−1 and are assigned to the O-H stretching and the overtone of O-H bending. For exposures higher than 1.0 L, the sticking coefficients are similar for different temperatures. The features in the O-H stretch region for water clusters red-shift as a function of temperature between 85 and 140 K. Water clusters have an amorphous structure between 85 and 140 K, and form a crystalline structure at 150 K. 相似文献
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A. Balzarotti M. Fanfoni F. Patella R. Sperduti F. Licci 《Physica C: Superconductivity and its Applications》1995,250(3-4):382-388
We have applied the phenomenological model of diffused interfaces, developed originally to describe the Fe growth on Bi2Sr2CaCu2O8, to interpret quantitatively the core photoemission spectra of two reactive interfaces, namely Cr and Ge on Bi2Sr2CaCu2O8. At room temperature the interfaces with Fe and Cr have the same kinetics of growth suggesting similar adatom condensation, while the semiconductor-superconductor interface grows layer-by-layer according to the Franck-van der Merwe kinetics. Differences in the parameters of the model resulting from the simultaneous fit of the core-level decays are related to differences in the microscopic processes occurring during the growth. 相似文献
14.
Wolf E. L. 《Superlattices and Microstructures》1996,19(4):305-312
It is clear that many of the cuprate superconductors are truly superlattices, composed of sheets whose individual superconducting critical temperatures may approach bulk values. Such a cuprate is Bi2Sr2CaCu2O8, often referred to as BSCCO-2212. Scanning tunneling spectroscopy (vacuum tunneling) applied toa-bBiO cleavage planes ofTc≈90 K BSCCO single crystals under liquid helium simultaneously provides topography and local dI/dVspectra (superconducting density of states: DOS). The spectra, which are similar to those obtained from angle-resolved photoemission spectroscopy, confirm a large gap parameter Δ(x,y) on the uppermost layer. The dI/dVspectra do not unequivocally select order parameter symmetry, but are probably consistent with d-wave or anisotropic s-wave states. Spatial variations of Δ on a 100 Å scale are attributed to variation in BiO metallicity, originating in oxygen stoichiometry variations. A model is presented to explain the different dI/dVspectra which are seen, and associated with different local oxygen concentrations. This model, based on the superconducting proximity effect, assumes that in some regions the BiO uppermost layer is insulating and in other regions it is metallic, in the latter case induced superconductivity by proximity to the CuO2planes. Our STM measurements appear to sample only the uppermost half cell of the crystal, and contain no obvious superlattice features. Recent measurements have confirmed Josephson radiation from voltage biasedc-axis pillars of BSCCO. From the point of view of the present work, the superconducting systems which weakly couple along thec-direction to create Josephson junctions are probably half-cell slabs of height 15.4 Å, each containing two CuO2and two BiO layers, which act as single composite electrodes for the Josephson junctions. 相似文献
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August Yurgens Dag Winkler Nicolay Zavaritsky Tord Claeson 《Czechoslovak Journal of Physics》1996,46(Z3):1293-1294
We report on thec-axis superconducting energy gap parameter Δ
c
(T) of intrinsic Josephson tunnel junctions inBi
2
Sr
2
CaCu
2
O
8+δ (Bi2212) single crystals. Δ
c
(4.2K)≈10−13 meV, which is approximately a factor of two smaller than reported in the majority of tunneling experiments. Δ
c
(T) deviates strongly from the BCS temperature dependence. These observations may be explained by a multilayer model of Bi2212
which assumes that theBi−O layers are superconducting due to the proximity effects. The Josephson tunneling then takes place between adjacentBi−O layers while there is a strong proximity coupling betweenBi−O andCu−O layers.
The work is supported by Swedish Supercon-ductivity Consortium and NUTEK, and, in part, by Russian Foundation for Basic Research,
grant #95-02-04307 相似文献
16.
实验研究了Bi2Sr2CaCu2-xSnxO8+δ 的X射线衍射(XRD)和光电子能谱(XPS).实验发现随着掺杂(Sn)量的增加,晶格参数a 和c都有所变化,O1s和Cu2p芯能级谱也发生了变化.实验结果表明: 在低掺杂量时,Sn主要 呈二价态;而在高掺杂浓度时呈四价态;掺Sn对超导电性的影响与其他元素的掺杂不同.这 些实验结果支持化学环境在高温超导样品的电子结构中起着重要作用的结论.
关键词:
Bi系超导体
掺杂
X射线衍射
光电子能谱 相似文献
17.
On melt processed samples of the 86 K superconductor Bi2Sr2CaCu2O8 we have performed resistive measurements in the low field limit B0.13 T and 40 KT77 K. The voltage drop is found to rise exponentially with current E ∝exp j/j0, which is interpreted in terms of thermal activation of pinned flux lines. An activation energy U0(T)90 meV is derived from the transition width j0(T) and is related to a plausible core pinning interaction of flux lines with normal conducting precipitates. This reproduces the measured jc(B, T) values in the whole regime investigated. We conclude that pinning centers must have a minimum size in order to control flux creep. Finally we demonstrate that conventional summation of the single site pinning forces cannot account for the observed macroscopic depinning current density. 相似文献
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We report measurements of anamolously large dissipative conductivities, σ1, in Bi2Sr2CaCu2O8+δ at low temperatures. We have measured the complex conductivity of Bi2Sr2CaCu2O8+δ thin films at 100–600 GHz as a function of doping from the underdoped to the overdoped state. At low temperatures there exists a residual σ1 which scales with the T=0 superfluid density as the doping is varied. This residual σ1 is larger than the possible contribution to σ1 from a thermal population of quasiparticles (QP) at the d-wave gap nodes. 相似文献
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J. Baak S.I. Mukhin H.B. Brom M.J.V. Menken A.A. Menovsky 《Physica C: Superconductivity and its Applications》1993,210(3-4):391-400
Specific heat data below 1 K of Bi2Sr2CaCu2O8 and YBa2Cu3O7 are analyzed. For YBa2Cu3O7 the nuclear specific heat, CN, amounts to 38T−2 μJ/mol K. CN for Bi2Sr2CaCu2O8 exceeds that of YBa2Cu3O7 by a factor of 15. The nuclear quadrupolar specific heat contribution alone is insufficient to explain the data for YBa2Cu3O7, while lack of NQR data does not allow such a comparison in Bi2Sr2CaCu2O8 to be made. The contribution to CN from nuclear spins coupled via the contact hyperfine interaction with correlated magnetic spins (in the CuO2 plane) is derived as a function of the correlation length. This contribution can be treated independently from the quadrupolar term. We show that the excess specific heat in YBa2Cu3O7 likely originates in a few percentage of an impurity (oxygen deficient) phase with a strong hyperfine field on the Cu nuclei. 相似文献
20.
H. Enriquez N. Bontemps P. Fournier A. Kapitulnik A. Maignan A. Ruyter 《Czechoslovak Journal of Physics》1996,46(Z3):1593-1594
We observe the lock-in transition in Bi2Sr2CaCu2O8+δ single crystals, by measuring the 10 GHz dissipation for various orientations of the magnetic field; various vortex lattice
structures are revealed by different dissipation regimes. 相似文献