由时间飞行光谱技术测量激光制膜过程中出射粒子的飞行速度

激光烧蚀沉积法是近几年迅速发展起来的新型高温超导薄膜以及超导微电子器件制备的一项重要工艺。实验研究表明,采用这种沉积方法能够实现超导薄膜的原位低温外延生长,进而易于获得性能优良的超导膜,其原因除了在制膜过程中靶面上各种元素具有     

准分子激光溅射法制备高温超导薄膜

利用准分子激光光束照射钇钡铜氧超导体,取得了零电阻温度为85K 的钇钡铜氧超导薄膜;研究了淀积条件与退火过程对薄膜成份及超导性能的影响。     

氧化物超导材料的进展

从超导合成粉、超导线材、超导熔融体、超导厚膜材料、弱磁场屏蔽体及超导薄膜材料等方面介绍了氧化物超导材料及其应用的进展。     

{011}〈UVW〉取向银基带的织构研究

由于Ag不与超导氧化物发生反应，在Ag基带上可以直接沉积YBa2Cu3O7-δ超导薄膜而不需过渡层，但基带的织构状态对超导膜的电性能有很大影响。研究表明{011}〈uvw〉取向的Ag基带有利于外延生长具有c取向及面内取向的YBa2Cu3O7-δ超导薄膜，进而使超导膜具有高的临界电流值。     

射频磁控溅射原位制备高Tc钇钡铜氧超导薄膜

用粉末靶射频磁控溅射的方法在650℃的(110)SrTiO_3衬底上成功地原位制备出起始转变温度96K,零电阻温度88.2K,用约0.4mm宽的桥在77K零磁场下临界电流密度达6×10~5A/cm~2,高度定向的钇钡铜氧超导薄膜,膜的厚度为0.22μm。发现控制溅射工艺参数并在溅射后进行原位热处理是获得高T_c超导薄膜的关键。     

激光复合扫描剥离法制备大面积薄膜

提出了一种新的制备大面积超导薄膜的方法.他人的方法是:基片运动或靶体倾斜运动或激光束运动.该方法是:基片不动, 采用光学变换系统,让脉冲激光按设定的象行星运动一样的轨迹旋转, 复合扫描剥离耙材, 淀积成薄膜.且提出了淀积厚度分布的理论模型, 模型中的参量均与实验参数联系起来, 从模型可以较容易地分析出膜厚分布的特点.这对改善实验条件, 获取厚度均匀的大面积超导薄膜具有直接的指导意义.理论计算和实际结果均表明该方法制得的薄膜面积较大, 厚度更均匀.得到的薄膜厚度均匀性大于0.95,面积可达几平方厘米,满足工业上微波超导器件等对薄膜的要求.(PE21)     

Ti-O化合物制备TiO2薄膜热处理及透射率研究

采用离子束辅助蒸发,以TiO2,Ti3O5,Ti2O3为膜料,制备了具有良好光学透射性的TiO2薄膜.结果分析表明,所制备出的TiO2薄膜均为非晶态结构,退火后薄膜发生晶化均具有明显的(101)择优取向;晶化的程度和退火温度的高低有关;退火处理之后以TiO2,Ti3O5为膜料制备的薄膜透射率下降,而以Ti2O3为膜料的上升;膜料不同对氧的需求量不同:以TiO2,Ti3O5为膜料制备薄膜所需氧量,远小于以Ti2O3为膜料所需氧量,氧流量过多降低了薄膜的透射性能,且随氧流量的不同,薄膜的透射率曲线均发生偏移,膜料不同偏移度也不同.     

ZnO薄膜的成分与电阻率的关系

为了弄清ZnO薄膜的导电机理及电阻率与工艺参数的关系,对薄膜的成分进行了精确测定。结果表明,电阻率主要受膜中Zn/O比的影响。对电导机理提出的模型认为,主要由导带电子传导和缺陷间跳跃电导决定膜的电导性能。膜中施主为氧空位,陷阱由填隙氧原子提供。当膜中Zn多于氧时,主要为导带电导,而氧多于Zn时,则以跳跃电导为主。     

中国超导应用获重大突破

令现代人惶恐的手机辐射遇到一个新的克星——超导薄膜。北京有色金属研究总院日前宣布，该院超导专家研制成功的“大面积双面高温超导薄膜”可使现有手机地面机站接收距离增长 一倍，如果北京的所有机站都用上“超导膜”，手机功率降低一半也可正常使用，相应的手机辐射也就大大降低。据该院超导研究中心主任林晨光介绍，超导材料除了“电阻为零”这种奇效外，还有另一种重要特性，就是具有普通材料所没有的微波效果，将超导薄膜应用在微波器件中，机站的接收灵敏性将大幅提高。广泛使用超导膜微波器件可降低机站密度，或是促使手机厂家降…     

用激光干涉法诊断准分子激光在YBa_2Cu_3O_(7-δ)靶表面激励的等离子体电子密度

目前氧化物高温超导薄膜的制备已有多种方法,其中准分子激光溅射法是最有前途的方法之一。准分子激光溅射法制备高温超导膜的最大特点就是其保成份性和高效率。由于其保成份性使得制备厚位超导膜成为现     

高温超导YBa2Cu3O7薄膜的颗粒,杂相生长机制研究

ＹＢａ２Ｃｕ３Ｏ７（ＹＢＣＯ）高温超导薄膜是重要的超导电子器件应用的材料，它们的质量对器件的运行性能至关重要。薄膜表面的颗粒使表面微波性能变坏，但有些生长在ＹＢＣＯ薄膜基体内部的小颗粒，会使薄膜的临界电流密度升高。     

Carbon‐Nanotube‐Templated,Sputter‐Deposited,Flexible Superconducting NbN Nanowire Yarns

Flexible superconducting yarns consisting of sputter‐deposited NbN nanowires on highly aligned carbon nanotube (CNT) array sheets are reported. In the microscopic view, the NbN nanowires are formed on top of individual CNT fibrils, and the superconductivity property of the twist‐spun NbN–CNT yarn system is comparable to that of a typical NbN thin film on a normal solid substrate. Because of its intrinsic porosity, the system exhibits superior mechanical flexibility with a small bending radius. It also remains a superconducting state even when subjected to severe mechanical deformations, primarily due to the proximity superconductivity through carbon nanotube bundles. The results demonstrate the possibility of fabricating flexible superconducting yarns in a conventional thin‐film deposition process, using ultraflexible free‐standing CNT sheets as a template. In addition, preliminary tests on reducing the normal‐state resistance toward superconducting cable applications are presented.     

Full-wave characterization of high-Tcsuperconducting transmission lines

A full-wave numerical analysis is applied to accurately characterize superconducting transmission lines embedded in a layered dielectric medium. A volume integral equation formulation is developed by using a spectral domain dyadic Green's function for stratified media. Galerkin's method with rooftop basis functions for the electric field distribution inside the superconductor is then employed to solve the complex propagation constant. The thickness of the superconducting film is arbitrary in this analysis, and the formulation rigorously accounts for the anisotropy of the superconducting film. The propagation characteristics of a superconducting microstrip transmission line with a thin dielectric buffer layer are investigated. A superconducting stripline configuration with an air gap is also studied     

On the application of complex resistive boundary conditions tomodel transmission lines consisting of very thin superconductors

A resistive boundary condition for the case where the resistivity is assumed to be a complex quantity is shown to be an accurate model for a superconducting film which is thin compared to the super-conducting penetration depth. The imaginary part of the conductivity is the dominant terms and is a measure of the inductive energy stored in the superconductor. Numerical solutions of superconducting microstrip are obtained and compared to experimental results and to analytic solutions for superconducting parallel-plate waveguides. Excellent agreement is found between experimental, analytical, and numerical results     

The effect of superconducting ground plane on microwavecharacteristics of unpatterned superconducting films in the mixed state

We microwave characteristics of a multilayer structure made of a type-II superconducting thin film and a dielectric substrate together with a superconducting ground plane is studied theoretically by using the model of the self-consistent treatment of vortex dynamics. The dependence of reflection coefficient on the temperature and static magnetic field is reduced owing to the existence of the superconducting ground plane, especially at temperatures near T_c and at higher fields. Comparison of the interesting oscillation phenomenon in the associated effective surface resistance between the Meissner state (b=0) and mixed state (b≠0) is made. We find that the superconducting ground plane not only strongly narrows down the resonant peak shape but also enhances the peak height. Finally, a similar layered structure made of a superconducting thin film on a dielectric substrate shielded by a buffer layer is also considered. We specifically demonstrate that the buffer layer has essentially no substantial influence on microwave reflectance, transmittance, and complex surface impedance. The role played by the buffer layer is in great contrast to that in a planar transmission line     

Properties of an electromagnetically coupled small antenna with asuperconducting thin-film radiator

This paper describes the structure and properties of a 900-MHz-band small antenna with a superconducting thin-film radiator operated by electromagnetic coupling. The radiation efficiency of the antenna with a λ/38 radiator reached 74% at 79 K. The loss in this antenna comprised mismatching loss and radiator loss caused by the surface resistance of the superconducting thin film. A simulation model with a meander-line radiator and a parallel line is also proposed. This model makes it possible to design a superconducting thin-film radiator which can be fabricated on a dielectric substrate by using the moment method without taking account of the dielectric substrate     

高温超导膜微波滤波器

我们用氧化锆单晶衬底GBCO高温超膜研制了超导膜悬微波低通滤波器。在77K测试获得:通带插损在0—2GHz,0—4GHz和0—6GHz通带内,分别为0.326dB,0.507dB和1.393dB。文中阐明悬置微带电路用于研制高介电常数衬底的高温超导微波无源器件是适宜的。     

直流磁控溅射法制备YBCO超导薄膜研究

文中采用直流磁控溅射法制备了YBCO超导薄膜,研究了镀膜过程中不同的气体总压、氧氩比、薄膜厚度以及退火温度对薄膜性质的影响,通过XRD分析,当总气压为40Pa、氧氩比为1：2、厚度为1μm、退火温度为800℃时,是薄膜生长的最佳条件。总气压过低,镀膜过程不能进行,气压过高,分子间自由程增加,溅射速率降低;氧氩比较低时,...     

Correction factor for determining the London penetration depth fromstrip resonators

The strip resonator technique is a popular way to measure the temperature (T)-dependent London penetration depth λ_L(T) in superconducting thin films. The temperature dependence can provide fundamental information about the superconducting energy gap and hence insight into the pairing mechanism. Since λ _L(T) characterizes the film's response to a magnetic field near the surface, it qualifies the suitability of the superconducting film for microwave device applications. There has been much controversy regarding the actual form of the temperature dependency, with some researchers reporting a weak-coupled Bardeen-Cooper-Schriefer (BCS)-like behavior and others favoring a Gorter-Casimir type fit. This paper shows that the disagreement can be at least partially attributed to a temperature sensitive term traceable to stray susceptance coupled into the resonator. The effect is inherent to the technique, but a simple procedure to compensate for it can be used and is presented here as a correction factor (1+ξ)     

高温超导带通滤波器

本文报道用LaAlO_3衬底GdBa_2Cu_3O_1高温超导薄膜研制的四极平行耦合带通滤波器。在77K测试,结果为:中心频率为8.96GHz,带内插入损耗为0.54dB,带宽为500MHz。文中还讨论了设计制作高性能微带滤波器应注意的问题。