金属有机溶剂法Y1Ba2Cu3O7-δ超导薄膜的Ce掺杂效应

通过三氟乙酸盐-金属有机物沉积方法（TFA-MOD）研究了Ce掺杂对钇钡铜氧（YBCO）超导薄膜性能的影响.观察到10 mol%Ce掺杂使YBCO超导薄膜的c轴取相降低,出现明显的a轴晶粒,薄膜表面变得粗糙.尽管超导临界温度稍有减小,其超导临界电流密度（Jc）在高磁场下性能获得了有效提高,当外磁场强度达到2T时,超导薄...     

湿度对YBCO薄膜微观结构和超导性能的影响

文中采用无氟高分子辅助金属有机物沉积法( PA - MOD)在不同湿度条件下在LaAlO3单晶基底上制备了一系列YBCO超导薄膜.X射线衍射、扫描电镜和物性测量的结果表明,在成相热处理过程中气氛湿度对YBCO薄膜的结构和超导性能的有明显影响.干燥气氛成相的YBCO薄膜织构较好,表面较平整、致密,超导性能也较高,其临界超...     

超导薄膜螺旋生长结构对临界电流密度的影响

本文用扫描隧道电子显微镜和原子力显微镜观察了不同实验条件一利用激光沉积技术制备的ＹＢｑａ２Ｃｕ３Ｏ７－ｘ超导薄膜的微观结构，并分析了薄膜细胞与超导电性的关系。螺旋生长结构能减少薄膜中的弱连结和在薄膜中形成磁通钉扎中心，因此使超导薄膜的临界电流密度比同类超导体材大得多。     

厚度诱导的YBa2Cu3O7-δ超导薄膜剩余应力及临界电流变化

本文通过脉冲激光沉积法制备了不同厚度(80nm、320nm、1000nm和2000nm)的YBa2Cu3O7-δ(YBCO)超导薄膜,对它们的剩余应力和临界电流特性进行了对比研究.通过系列的激光显微Raman光谱和磁化曲线测量分别获得了薄膜剩余应力和磁化临界电流密度(Jc)对薄膜厚度的依赖关系.结果显示超导薄膜内剩余应力越小,Jc越高.对于中等厚度的薄膜样品(320nm和1000nm),其膜内剩余应力较小,同时由其特征的磁通匹配场大小推知在该厚度范围内的样品具有较高的线性缺陷密度,从而显示出较高的Jc值.     

短时高温热处理工艺对YBCO超导薄膜结构和性能的影响

通过无氟高分子辅助金属有机物沉积法(PA-MOD)制备了YBCO超导薄膜,研究了785～845℃的不同短时高温热处理对YBCO薄膜双轴织构、表面形貌及超导性能的影响.X射线衍射(XRD)和扫描电镜(SEM)的结果表明,经800℃短时高温处理的YBCO薄膜具有良好的双轴织构和平整致密的表面形貌.物性测量(Quantum-DesignSQUID)的结果表明,该薄膜超导转变温度达到90K,77K自场下的临界电流密度(Jc)为2MA/cm2.     

石墨掺杂MgB2线材制备及其超导性能研究

利用原位粉末套管法制备出石墨掺杂的MgB2-xCx/Fe (x= 0.00, 0.05, 0.10)超导线材,采用两种工艺制度对线材进行了最终热处理.结果显示,石墨掺杂可以有效地提高MgB2线材的临界电流密度(Jc)和磁通钉扎力(Fp).常规热处理线材的Jc(B)和Fp(B)性能均优于快速热处理的,其主要原因是不同热处理制度导致的显微结构差异.     

钛酸锶衬底表面改性对YBCO高温超导薄膜性能的影响北大核心CSCD

YBa_2Cu_3O_(7-x)(YBCO)高温超导材料在高温高场中具有比较高的临界电流密度,因此具有较好的应用前景.通过研究YBCO高温超导薄膜,以提高它的载流能力和超导性能是市场应用的迫切需要.文中所研究的钛酸锶(SrTiO_3)衬底,作为一种钙钛矿结构,不仅具有良好的化学和热稳定性,而且与YBCO高温超导薄膜具有较小的晶格失配度.通过酸腐蚀法和无酸腐蚀处理钛酸锶SrTiO_3(100)(STO)衬底,运用原子力显微镜观察了两种衬底处理方法对钛酸锶衬底表面结构的影响.并在其上用三氟乙酸盐金属有机沉积法(TFA-MOD)制备出临界密度达到约2.50~3.00 MA/cm^2的YBCO高温超导薄膜.通过四引线法表征YBCO高温超导薄膜的Tc达到了均约93K.通过扫描电子显微镜(SEM)分析了衬底处理技术的不同对其表层生长的YBCO高温超导薄膜形貌的影响.通过X射线衍射仪(XRD)固定方位角法表征了不同的衬底处理技术对薄膜内的残余应力的影响.     

石墨掺杂MgB2线材制备及其超导性能研究

利用原位粉末套管法制备出石墨掺杂的MgB2-xCx／Fe（x=0．00，0．05，0．10）超导线材，采用两种工艺制度对线材进行了最终热处理．结果显示，石墨掺杂可以有效地提高MgB2线材的临界电流密度（Jc）和磁通钉扎力（Fp）．常规热处理线材的Jc（B）和Fp（B）性能均优于快速热处理的，其主要原因是不同热处理制度导致的显微结构差异．     

添加Sm211对MTG—Y123临界电流密度的影响

适量Ｓｍ２ＢａＣｕＯ５（Ｓｍ２１１）的掺入改善了熔融织构ＹＢａ２Ｃｕ３Ｏｙ（ＭＴＧ－Ｙ１２３）的临界电流密度特性，并且在磁化曲线中出现第二峰现象（鱼尾现象）。在９５０℃进行高温处理后，第二峰消失，并且临界电流密度也降低了，其后的吸氧处理不能完全恢复后处理的临界电流密度特性。这可能是因为形成了（Ｙ，Ｓｍ）１２３，且局域富Ｓｍ的（Ｙ，Ｓｍ）１２３中Ｓｍ代替Ｂａ形成低Ｔｃ相造成的。我们还对比了加及不加Ｓ     

Texture analysis of RF-sputtered CeO2 buffer layers and superconducting MOD-YBCO films

CeO₂ buffer layers were deposited on YSZ single-crystal substrates using an RF-sputtering method. The development of crystalline textures of sputtered CeO₂ films at different sputtering pressure and their effects on YBCO films, deposited by Metal Organic Deposition (MOD), were investigated. Both CeO₂ and subsequent YBCO films grew well epitaxially. The relative XRD peak intensities of CeO₂ (2 0 0) to substrate YSZ (2 0 0) increased with deposition pressure in the range of 3–5 mTorr and were inversely proportional to the θ–2θ scan FWHM values of CeO₂ (2 0 0). Also, the reaction layers of BaCeO₃ were thicker in the samples with lower CeO₂ (2 0 0) intensities and poor out-of-plane alignment when CeO₂ were deposited at the lower pressure of 3.3 mTorr. It is noted, however, that the superconducting layer grew well epitaxially on these BaCeO₃ layers, possibly due to the epitaxial relation between CeO₂ and YBCO. The superconducting critical currents of MOD-YBCO films showed an increasing tendency as both the Δ2θ (CeO₂) and BaCeO₃ peak intensities decreased.     

计算晶体CdCl2:Ni2+的电子顺磁共振谱的完全对角化和高阶微扰方法

采用半自洽场自由Ni²⁺的d轨道波函数和点电荷-偶极子模型,建立局部结构、光谱与电子顺磁共振(EPR)谱(零场分裂D和顺磁g因子)之间的定量关系.利用完全对角化方法(CDP)和高阶微扰方法,统一解释CdCl₂:Ni²⁺晶体的局部结构、光谱和电子顺磁共振谱(EPR),并比较两种计算方法得到的结果.     

Homoepitaxial growth of MOD-YBCO thick films on evaporated and MOD templates

We have prepared metal organic deposition (MOD)-YBCO thick films by repeating the coating-pyrolysis-crystallization procedure onto ～100-nm-thick evaporated and MOD templates. Surface morphology of the template was found to strongly affect the homoepitaxial growth of MOD-YBCO layers on the template; namely, the epitaxial growth of MOD-YBCO on the evaporated template was much easier than that on the MOD template. A 220-nm-thick epitaxial MOD-YBCO film was successfully prepared on the 100-nm-thick evaporated-YBCO template to obtain a 320-nm-thick YBCO film, which exhibited J_c = 2.44 MA/cm² and I_c = 78 A/cm. The I_c value has significantly increased from 37 A/cm for the evaporated-template.     

Effects of thickness on superconducting properties and structures of Y_2O_3/BZO-doped MOD-YBCO films

We report the thickness dependence of critical current density(J c) in YBa2Cu3O7-x(YBCO) films with BaZrO3(BZO) and Y2O3 additions grown on single crystal LaAlO3 substrates by metalorganic deposition using trifluoroacetates(TFA-MOD). Comparing with pure YBCO films, the J c of BZO/Y2O3-doped YBCO films was significantly enhanced. It was also found that with the increase of the thickness of YBCO film from 0.25 μm to 1.5 μm, the I c of BZO/Y2O3-doped YBCO film increased from 130 A/cm to 250 A/cm and yet J c of YBCO film decreased from 6.5 MA/cm2 to 2.5 M A/cm2.The thick BZO/Y2O3-doped MOD-YBCO film showed lower J c, which is mainly attributed to the formation of a-axis grains and pores.     

Ni~(2+):CsMgCl_3的光学吸收谱和EPR的研究

应用三角晶场中d2 (d8)电子组态包括静电相互作用和自旋 轨道耦合作用的强场能量矩阵 ,采用完全对角化方法 ,精确地计算了具有D3d 对称的Ni2 + :CsMgCl3 的光学吸收谱和EPR谱。理论结果与实验值符合得很好。     

Ni~(2+):LiNbO_3的光学吸收谱和EPR的研究

应用三角晶场中d2 (d8)电子组态的包括静电相互作用和自旋 轨道耦合相互作用的强场能量矩阵 ,采用完全对角化方法 ,精确地计算了具有C3V 对称的Ni2 +:LiNbO3 的光学吸收谱和EPR谱。理论结果与实验值符合得很好     

Er~(3+)和Yb~(3+)/Er~(3+)掺杂对石英光纤中倍频的影响

实验研究了掺Er~(3+)和Yb~(3+)/Er~(3+)石英光纤中的倍频过程.测量了不同Er~(3+)和Yb~(3+)/Er~(3+)掺杂量的光纤倍频转换效率和光纤倍频预处理前后Er~(3+)发射可见荧光的强度,探讨了Er~(3+)和Yb~(3+)掺杂对光纤中倍频过程的影响.     

Effects of nitrogen doping on optical properties of TiO2 thin films

The potential for extending the optical absorption range of TiO₂ by doping with nonmetallic elements was examined in nitrogen-containing TiO₂ thin films. Thin films of TiO_2-xN_x were synthesized on glass and silicon substrates by ion-beam-assisted deposition to obtain a wide range of nitrogen concentrations. The compositions of the films were determined by Rutherford backscattering spectrometry and X-ray photoelectron spectroscopy. The structures of the films were analyzed by X-ray diffraction, transmission electron microscopy, and atomic force microscopy. The optical properties of the films were measured by UV-Vis spectroscopy and ellipsometry. A characteristic decreasing trend in band-gap values of the films was observed within a certain range of increasing dopant concentrations. As the nitrogen concentration increased, the structure of the films evolved from a well-defined anatase to deformed anatase. The reduced band gaps are associated with the N 2p orbital in the TiO_2-xN_x films. PACS 78.66.-w; 78.20.Ci     

Effect of Co doping on CIS2 thin films

In recent years, substantial scientific attention has been focused on renewable energy resources, which utilize natural resources for the production of electrical energy. Chalcopyrite semiconductors are used as one of the alternatives, Cu(In,Ga)Se₂ (CIGS) and CuInS₂ (CIS) are used for the fabrication of solar cells. These materials possess various properties Viz. ideal band gap (1.5?eV), high optical absorption, low light degradation, high radiation resistance, etc., hence they are suitable in the fabrication of solar cells. In contrast to other chalcopyrates, CuInS₂ is nontoxic, low-cost and easy to prepare by simple deposition techniques. Several impurities were doped to CuInS₂ bulks, to control conduction and also to obtain low resistivity. In this context, the structural, morphological and optical properties are reported for cobalt-doped CuInS₂ (CIS₂) thin films prepared by electro-deposition technique at room temperature. In the present study, we have used different cobalt concentration in the range of 0–5?wt.%. Doping of cobalt does not lead to the formation of any secondary phase, either in the form of metallic clusters or impurity complexes. However, with increase in cobalt concentration a decrease in the optical band gap, from 2.10 to 1.53?eV, is observed. In addition, implantation of cobalt in the CIS₂ gave changes in structural and surface properties of the thin films obtained. These thin films are also subjected to elemental analysis using EDAX.     

Influence of varied doping structure on photoemissive property of photocathode

The built-in electric fields within a varied doping GaAs photocathode may promote the transport of electrons from the bulk to the surface,thus the quantum efficiency of the cathode can be enhanced remarkably. But this enhancement,which might be due to the increase in either the number or the energy of electrons reaching the surface,is not clear at present. In this paper,the energy distributions of electrons in a varied doping photocathode and uniform doping photocathode before and after escaping from the cathode surface are analysed,and the number of electrons escaping from the surface in different cases is calculated for the two kinds of photocathodes. The results indicate that the varied doping structure can not only increase the number of electrons reaching the surface but also cause an offset of the electron energy distribution to high energy. That is the root reason for the enhancement of the quantum efficiency of a varied doping GaAs photocathode.