高Tc超导材料微结构的透射电镜研究

报导了高Ｔｃ材料的透射电镜研究。结合材料的物理性能，对ＹＢａ２Ｃｕ３Ｏｘ中氧的含量及有序、ＹＢａ２Ｃｕ３Ｏｘ融熔织构材料和Ｂｉ２Ｓｒ２ＣａＣｕ２Ｏｘ／ＭｇＯ复合材料中的晶界，以及高Ｔｃ薄膜和多层膜的结构进行了分析。     

Bi4Ti3O12铁电薄膜的I—V特性测量及导电机理

Ｂｉ４Ｔｉ３Ｏ１２薄膜是一种具有广泛应用前景的典型的铁电薄膜。本文报道了用ＭＯＣＶＤ方法制备的Ｂｉ４Ｔｉ３Ｏ１２薄膜的Ｉ－Ｖ特性测量及其导电机理。结果表明，在低场下，Ｂｉ４Ｔｉ３Ｏ１２薄的Ｉ－Ｖ特性表现为欧姆性质，在中强场下，薄膜的导电机理遵从ＳＣＬＣ理论。     

镍基合金上离子束辅助沉积双轴取向的YSZ膜—YBCO超导膜缓冲层

用双离子束辅助沉积（ＩｏｎＢｅａｍＡｓｉｓｔｅｄＤｅｐｏｓｉｔｉｏｎ，ＩＢＡＤ）方法在Ｎｉ－Ｃｒ合金上合成了具有（００ｌ）择优取向，平面双轴排列的ＹＳＺ膜（Ｙ２Ｏ３－ＺｒＯ２）作为ＹＢＣＯ超导膜缓冲层。辅助轰击离子束方向与衬底法线的夹角５４０左右时可获得最佳的（００ｌ）择优效果。８０００Ｃ高温退火后其结构有较大的改善。在其上用ＭＯＣＶＤ方法生长的ＹＢＣＯ膜的Ｔｃ＝８８Ｋ，Ｊｃ＝１０×１０４Ａ／ｃｍ２（０Ｔ，７７Ｋ），并且从Φ扫描的结果说明了ＹＳＺ缓冲层上ＹＢＣＯ膜的生长机制。     

常压MOCVD制备MgO薄膜的研究

本文首次报道用常压金属有机化学气相沉积（ＡＰ－ＭＯＣＶＤ）在Ｓｉ（１００），ＳｉＯ２／Ｓｉ（１００）和Ｐｔ／Ｓｉ（１００）衬底上外延高质量的ＭｇＯ薄膜。研究了衬底温度与薄膜的取向性关系和ＭｇＯ薄膜的潮解特性。高纯ｍａｇｎｅｓｉｕｍａｃｅｔｙｌａｃｅｔｏｎａｔｅ［ｂｉｓ（２，４－ｐｅｎｔａｎｅｔａｎｅ－ｄｉｏｎｏ）ｍａｇｎｅｓｉｕｍ］［Ｍｇ（ＣＨ２ＣＯＣＨ２ＣＯＣＨ３）２］作为金属有机源，扫描电镜（ＳＥＭ），透射电镜（ＴＥＭ）和Ｘ－ＲＡＹ衍射实验显示，在较低的衬底温度（～４８０℃）下一次淀积成单晶膜。薄膜均匀，致密，结晶性和取向性很好，衬底温度（Ｔｓ）在４００℃到６８０℃之间，在Ｓｉ（１００）衬底上生长的ＭｇＯ薄膜都具有［１００］取向，在Ｓｉ（１００）、ＳｉＯ２／Ｓｉ（１００）和Ｐｔ／Ｓｉ（１００）衬底上生长的ＭｇＯ薄膜也都具有［１００］取向。     

Bi_4Ti_3O_（12）铁电薄膜的I－V特性测量及导电机理

Ｂｉ＿４Ｔｉ＿３Ｏ＿（１２）薄膜是一种具有广泛应用前景的典型的铁电薄膜。本文报道了用ＭＯＣＶＤ方法制备的Ｂｉ＿４Ｔｉ＿３Ｏ＿（１２）薄膜的Ｉ－Ｖ特性测量及其导电机理。结果表明，在低场下，Ｂｉ＿４Ｔｉ＿３Ｏ＿（１２）薄膜的Ｉ－Ｖ特性表现为欧姆性质，在中强场下，薄膜的导电机理遵从ＳＣＬＣ理论。     

溶胶—凝胶技术制备Bi4Ti3O12铁电薄膜的研究

采用溶胶－凝胶技术在Ｓｉ单晶基片上制备了具有层状钙钛矿型结构的Ｂｉ４Ｔｉ３Ｏ１２ｘ铁电薄膜，讨论了回火温度与时间对薄膜结构的影响，Ｘ射线衍射分析表明，经７００℃和７００℃以上温度回火的薄膜为具有层状钙矿型结构的Ｂｉ４Ｔｉ３Ｏ１２多晶薄膜，该薄膜的电滞回线测试呈出剩余极化强度Ｐｒ＝５μＣ／ｃｍ＾２，矫顽场Ｅｃ＝１３０ｋＶ／ｃｍ。     

铁基巨磁阻抗薄膜的研究

溅射方法制备的非晶Ｆｅ６８Ｃｕ０．５Ｃｒ４Ｖ５Ｓｉ１３．５Ｂ９薄膜,通过适宜的退火处理得到具有纳米ａ－Ｆｅ（Ｓｉ）和非晶母相的混合结构和最佳的软磁性能,相应的巨磁阻抗值最高可达７２％。本着重研究了热处理条件、薄膜组织结构、较磁性能以及驱动电流频率对Ｆｅ６８Ｃｕ０．５Ｃｒ４Ｓｉ１３．５Ｂ９薄膜磁致阻抗的影响。     

（BiAl）YIG薄膜的生长感生磁各向异性

从理论和实验上分析了Ｆｅ＾３＋和Ｆｅ＾２＋对（ＢｉＡ）ＹＩＧ薄膜的生长感各向异性的贡献，掺Ｂｉ导致的生长磁感生各向异性，来源于Ｅｉ＾３＋改变了Ｆｅ＾３＋的零场劈裂，其大小取决于Ｂｉ＾３＋含量及在十二面体位的择优分布，高价离子和氧空位形成的Ｆｅ＾２＋在八面体位的择优分布，对生长感生磁各向异性也有贡献。     

乙烯对CVD法制备硅薄膜性能的影响

以硅烷和乙烯的混合气体的原料气,通过常压化学气相沉积方法在玻璃衬底上生长出了硅薄膜。结合光电子能谱、高分辨电镜以及薄膜抗腐蚀性研究,证实乙烯的引入使硅薄膜中形成一定数量的ＳｉＣ微晶粒。ＳｉＣ较高的化学稳定性使薄膜具有较强的耐碱性,而其较小的折射率使薄膜的镜面反射率较高低。含有ＳｉＣ的硅薄膜经碱液适当腐蚀后能降低镜面反射,进而有可能减少光污染现象。     

液相外延生长磁性石榴石薄膜中铋的分凝系数与生长率的关系

在Ｂｉ２Ｏ３－ＰｂＯ－Ｂ２Ｏ３复合助熔剂中，采用等温浸渍液相外延技术在ＧＧＧ基片的（１１１）面上生长了（Ｂｉ，Ａｌ）：ＹＩＧ薄膜。通过调整过冷度和基片转速来改变薄膜的生长速率。测量了外延膜中铋的含量。给出了铋的分凝系数的表达式，并计算了铋的分凝系 。     

Current and Temperature Dependent Matching Fields in Nb Film of Rectangular Array of Holes

Nanoengineered periodic array of holes on superconducting thin films have a great interest due to their excellence for the studies of the vortex pinning mechanisms in the type-II superconductors. Rectangular array of holes has been fabricated over a microbridge of Nb superconducting thin film by e-beam lithography. Rectangular array of holes have two type of scenario, at low magnetic fields matching effects are sharp and narrow while at high fields wide and shallower. In this work, we study the matching pinning effect by the artificial hole array in superconducting Nb thin films. We observed that as the inter distance between holes is decreased; the sharp matching effects become dominant and vice versa.     

激光沉积高温氧化物超导薄膜

本文简要介绍激光沉积技术的原理、特点及国外科研机构采用这种方法制作陶瓷氧化物高温超导薄膜的技术参数等。本文还探讨了激光沉积超导薄膜的形貌及激光束与靶材的交互作用情况,并展望了这种技术的应用前景。     

Thickness-Dependent Current Density and Flux Distribution in Thin Current-Carrying Superconducting Films Exposed to a Magnetic Field

With the rapid development of high-temperature superconductors, it is of great significance to get the precise current density and flux distribution within thin high-temperature superconducting films subjected to a transport current and an applied magnetic field. The transport current distribution and flux density in thin high-temperature superconducting films are calculated by a numerical method based on the Kim model and exponential model in this paper. The influences of transport current, applied magnetic field, width, and thickness of a superconducting film on the current distribution are discussed. The results reveal that the thickness has a significant effect on the critical current density of superconducting films.     

先驱硼薄膜的质量对MgB2超导薄膜的影响

以高纯乙硼烷(B2H6)为B源,采用化学气相沉积(CVD)方法在多晶Al2O3衬底上沉积B薄膜,然后在Mg蒸气中异位退火来制备MgB2超导薄膜.通过X射线衍射和MgB2超导薄膜的电阻-温度曲线,研究了先驱硼薄膜的质量对MgB2超导薄膜的影响.     

FeSe超导薄膜的研究进展

FeSe及其相关化合物的高温超导性引起了凝聚态物理研究人员的广泛关注。在所有铁基超导体中,FeSe的成分和晶体结构最为简单,只存在铁基超导体最基本的结构单元FeSe层。FeSe超导体具有特殊的电子结构和物理特性,是铁基高温超导机制研究的理想平台。2012年,薛其坤组在SrTiO_3(STO)衬底表面采用分子束外延(MBE)法生长了单层FeSe薄膜,发现该体系的超导转变温度(TC)有接近80K的迹象,引起人们的广泛关注。先简要地介绍了FeSe晶体,FeSe/石墨烯薄膜的超导特性,再详细介绍了FeSe/SrTiO_3高温超导薄膜的输运性质、超导特性、电子结构以及可能影响单层FeSe/SrTiO_3薄膜高温超导的几个因素。     

Electrical conductivity and transition temperature of NbN thin films

Niobium nitride thin films are grown using reactive RF sputtering technique for four different partial nitrogen pressures in argon atmosphere. The superconducting transition temperature of the films has been measured. The films exhibit a negative temperature coefficient of resistivity. The electrical characterization of the films has been carried out and the conductivity measured between room temperature and liquid nitrogen temperature. This is fitted usingT ^P law.     

Cathodoluminescence microscopy of high T c superconducting YBCO and BSCCO materials

Spectroscopic and imaging cathodoluminescence (CL) microscopy has been used to study high T _c YBCO and BSCCO superconducting thin films and pellets in the scanning electron microscope. The effects of beam parameters, such as voltage, current, and diameter, have been investigated with a view to optimizing the CL signal intensity whilst preventing sample damage. Limiting the CL signal generation volume to within the thin film is important in eliminating any substrate contribution. Areas of strong luminescence have been observed in YBCO and BSCCO pellets as well as BSCCO thin films. At low beam energies, there is some correlation between the CL and secondary electron images. The CL spectra of the strongly luminescent spots differed from those of the poorly luminescencing superconducting phases. CL was able to identify a copper-rich impurity phase in the BSCCO material, and a barium cuprate phase in the YBCO material. It is proposed that the quality of a thin film, with respect to impurities, can be monitored using CL.     

Temperature and Current Dependent Matching Fields in?Superconducting NbN Film

Patterned superconducting thin films having a periodic array of submicrometric pinning centers have been of great interest due to their excellence for the studies of the vortex pinning mechanisms in the type-II superconductors. Square hole array has been fabricated over a micro-bridge 60 mm??60 mm of NbN thin film by electron beam lithography. Previous works have been carried out in Nb, Pb and Al thin films where the vortex pinning effect is assumed to be small. In this work, we study the matching pinning effect by the artificial hole array in superconducting NbN thin films. We observed the interplay between the vortex quantization and the artificial hole array. Magneto-resistance minima at integer matching fields up to five times of H ₁ (the first matching field corresponding to one vortex inside each hole) and fractional matching fields at 1/2H ₁, 3/2H ₁ and 5/2H ₁ have been observed.     

Characterization of Superconducting Thin Films Using a Generic Property of Resonators

A complete characterization of high-temperature superconducting films, as a function of microwave power, must track changes of the surface resistance and the penetration depth. A key problem has always been tracking power-dependent nonlinearities associated with a change in penetration depth. In this paper, we report a technique which exploits the generic response of resonators to a microwave impulse. We show that a transient response is observed which has a frequency equal to the difference between the driving frequency and the resonant frequency of the resonator. Moreover, we demonstrate how this transient response can be used to determine the nonlinear properties of superconducting thin films.     

Characterization of Superconducting Thin Films Using a Generic Property of Resonators

A complete characterization of high temperature superconducting films, as a function of microwave power, must track changes of the surface resistance and the penetration depth. A key problem has always been tracking power-dependent nonlinearities associated with a change in penetration depth. In this paper we report a technique that exploits the generic response of resonators to a microwave impulse. We show that a transient response is observed which has a frequency equal to the difference between the driving frequency and the resonant frequency of the resonator. Moreover, we demonstrate how this transient response can be used to determine the nonlinear properties of superconducting thin films.