电子通道技术在YBa2Cu3O7外延超导薄膜研究中的应用

本研究采用电子通道技术（ＥＣＰ）对单晶和双晶外延生长的ＹＢａ＿２Ｃｕ＿３Ｏ＿７（ＹＢＣＯ）超导薄膜的结构、取向和表面完好性作检测，并证实对衬底的预处理可改善外延超导薄膜的质量；还对ＹＢＣＯ／ＣｅＯ＿２／ＭｇＯ／ＳｒＴｉＯ３的双外延薄膜作研究。     

YBCO／Y－ZrO＿2／（1120）蓝宝石多层膜超导材料的分析电镜研究

我们在具有Ｙ稳定的ＺｒＯ＿２（ＹＳＺ）层的蓝宝石上获得高质量的ＹＢａ＿２Ｃｕ＿３Ｏ＿７（ＹＢＣＯ）高温超导薄膜。在零磁场下，７７ｋ时，其临界电流密度达到１．６×１０￣６Ａ／ｃｍ￣２。本文确定了多层膜超导材料的取向关系。ＹＢＣＯ膜的（００１）面平行于ＹＳＺ过渡层的（１００）表面。ＹＳＺ层厚为２０ｎｍ。并且，由于Ｂａ自ＹＢＣＯ层的外扩散，ＹＳＺ层含有Ｂａ。尽管蓝宝石与ＹＳＺ层间的晶格铅配很大，由于ＹＳＺ层具有［１００］择优取向，仍能获得准单晶的ＹＢＣＯ薄膜。在ＹＢＣＯ薄膜中，观察到均匀分布的、微小尺寸的Ｙ＿２ＢａＣｕＯ＿５（２１１相）沉淀粒子，它们也有利于提高临界电流密度。     

YBa2Cu3O7／PrBa2Cu3O7／SrTiO3超薄膜表面螺旋位错的研究

本文报道了用原子力显微镜（ＡＦＭ）研究的几种（ＹＢＣＯ）超薄膜的表面结构，这些膜分别生长在ＳｒＴｉＯ３（１００）基底，和具有厚度为４０ｎｍ的ＰｒＢａ２Ｃｕ３Ｏ７缓冲导的ＳｒＴｉＯ３基底上，ＹＢＣＯ超薄膜厚度范围为２．５ｎｍ－２５ｎｍ。在２．５ｎｍ厚的单层膜表面观察到了岛状结构，并在７．５ｎｍ厚的超薄膜表面首次观察到了台阶高度度不同的三种螺旋位错。同时还讨论了ＹＢＣＯ超薄膜的生长机理。     

激光诱导Y1Ba2Cu3Ox超导靶等离子体发射光谱的研究

利用ＯＳＭＡ光谱测量方法对Ｎｄ：ＹＡＧ激光烧蚀沉积Ｙ－Ｂａ－Ｃｕ－Ｏ超导薄膜过程中等离子体发射光谱的研究表明，靶表面喷出的粒子中存在着Ｙ，Ｂａ，Ｃｕ原子和离子以及氧化物光谱，其中Ｃｕ离子的光谱很少。     

高温超导薄膜电子显微结构的研究

本文报导了超导实验室用Ｈ９０００ＮＡ分析型电镜观察高温超导薄膜的结果，表明：激光淀积的ＹＢＣＯ薄膜易于出现非超导的大颗粒，提高了薄膜的表面微波电阻。但工艺若掌握得好时可生成单晶薄膜，适用于无源微波器件。     

准分子激光扫描淀积PZT/YBCO结构铁电薄膜

利用脉冲准分子激光（工作气体ＸｅＣｌ，波长３０８ｎｍ，脉宽２８ｎｓ）在外延ＹＢＣＯ／ＬａＡｌＯ３（１００）单晶基片上淀积了Ｐｂ（Ｚｒ０．５５Ｔｉ０．４５）Ｏ３铁电薄膜，ＹＢＣＯ薄膜既为生长高取向ＰＺＴ薄膜提供了晶体匹配条件，同时也为ＰＺＴ铁电薄膜提供了下电极。讨论了工艺参数对晶相结构和表面形貌的影响。用Ｘ射线衍射表征了该多层膜的晶相结构，扫描电镜观察其表面形貌。ＰＺＴ铁电薄膜的剩余极化为２１μＣ／ｃｍ２，矫顽场为６５ｋＶ／ｃｍ。     

硅上溅射BSCCO薄膜的微结构分析

重点研究了利用偏轴射频溅射的方法在Ｓｉ衬底上生长ＹＳＺ（Ｙ稳定的ＺｒＯ２）缓冲层及Ｂｉ－Ｓｒ－Ｃａ－Ｃｕ－Ｏ超导薄膜的工艺，获得了８２Ｋ的超导转变温度（Ｔｏｎ）。利用扫描原子显微镜和原子力显微镜对不同条件下生长的ＹＳＺ和ＢＳＣＣＯ薄膜进行了观察，提出了ＹＳＺ晶粒填补Ｓｉ衬底上针孔的新功能，并验证了ＢＳＣＣＯ薄膜的螺旋柱状生长机理。     

纳米YBCO颗粒的团聚的TEM研究

纳米超导颗粒ＹＢａ2 Ｃｕ3 Ｏ7 ｘ是制备第二代高温超导带材非常有用的原料。我们研究的纳米超导颗粒ＹＢａ2 Ｃｕ3 Ｏ7 ｘ是采用柠檬酸盐热解法制备的[1] 。这种方法不同于传统制备大块样品的粉末冶金法 ,可以制备非常细小的颗粒。超导颗粒的颗粒度对纳米带材涂层的质量 ,以及颗粒结晶度的情况对Ｔｃ和Ｊｃ具有重要影响。自ＹＢａ2 Ｃｕ3 Ｏ7 ｘ 的高分辨结构像被ＨｉｒａｇａＫ[2 ] 得到以来 ,对超导材料的ＴＥＭ研究集中在大块材料和薄膜材料[3 ] ,只有非常少的工作报道了纳米ＹＢＣＯ颗粒的ＴＥＭ研究[4] 。本文将对氧气氛退火的纳米Ｙ…     

微透镜和高Tc超导红外探测器组件

本文首次报道了利用微透镜阵列来提高ＹＢＣＯ高Ｔｃ超导薄膜红外探测器的光响应特性，介绍了利用光刻／离子束刻蚀的方法制作单片线列石英微透阵列的工艺以及制备线列ＹＢＣＯ高Ｔｃ超导薄膜红外探测器的方法，并将所制的石英微透镜阵列应用于ＹＢＣＯ超导器件。     

YBCO薄膜的PHREM研究

ＹＢＣＯ薄膜截面样品的高分辨电子显微镜（ＸＨＲＥＭ）研究已有报导［１，２］。它能给出薄膜与衬底之间的界面结构，薄膜的取向和缺陷等结构特征，为制备高质量的薄膜提供依据。与之相比，ＹＢＣＯ平面样品的高分辨电子显微镜（ＰＨＲＥＭ）研究则能给出较大区域的薄膜...     

Fabrication of MOD-derived YBCO films on [001]LaAlO/sub 3/ and their application to /spl lambda//4 CPW SIR BPFs

Chemically derived epitaxial thin films of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) are fabricated on [001]LaAlO/sub 3/ substrates by the metalorganic-deposition (MOD) process, which has advantages of high quality, nonvacuum, low-cost, and large-scale production of high-T/sub c/ superconducting films. The MOD-derived YBCO films have a sharp transition at the critical temperature (90.4 K) and a high-quality film with a surface resistance of 0.13 m/spl Omega/ (30 K, 9.98 GHz) is obtained. As a microwave application, simple and compact bandpass filters (BPFs) using /spl lambda//4 coplanar-waveguide. stepped-impedance resonators are demonstrated on the YBCO films. A two-stage Chebyshev BPF of center frequency of 5.731 GHz, bandwidth of 135 MHz, and insertion loss of 0.29 dB with little input power dependency in a power range less than 10 dBm is realized on the film.     

Excimer laser patterning of high-Tcsuperconducting thin films of YBCO

The patterning by excimer laser ablative etching of thin superconducting films of YBCO on MgO and fused silica substrates which were fabricated by laser sputtering is discussed. The etch rate as a function of laser fluence, wavelength, and number of pulses has been investigated. Although etched film surfaces were found to be considerably smoother than annealed films, the laser etching itself was found not to be a totally thermal process     

Preparation and characterization of YBaCuO high Tcsuperconducting thin films

For thin film metalorganic chemical vapor deposition (MOCVD), a stoichiometric gas phase can be obtained from a mixture of the precursors in the desired mole ratios, in spite of differences in the volatilities of the individual compounds. Proper film composition is obtained by controlling the velocity of a carriage containing the precursors through the heating zone of a vaporizer. YBaCuO (YBCO) superconducting films were prepared on yttrium stabilized zirconia (YSZ) (001) crystal substrates by single source MOCVD using a mixture of powders of Y(thd)₃, Ba(thd)₂ and Cu(thd)₂ as sources. Nondestructive measurements of resistivity, critical current, composition, and surface morphology were performed on these films. A single crystal film with T_co=89 K was made under optimum conditions. Its homogeneity was investigated by resistivity and T_co measurements and by atomic force microscopy (AFM) at several points of the surface along a diameter of this film. The roughness of the film is higher at the edge than at the center, and this appears to be correlated with the normal state resistivity. The c-axis and a-axis YBCO phases compete with each other at substrate temperatures ranging from 750 to 820°C. The c-axis YBCO phase shows spiral growth structure and the spiral step height is about 12     

超导电子学初探

本文叙述了几种超导晶体管模型,并提出在无缓冲层的Si及GaAs衬底上淀积高温超导体YBCO薄膜是困难的,只有缓冲层材料才能改善超导薄膜的质量。     

Superconductivity of YBCO Thick Films Prepared by Spark Plasma Sintering

YBa₂Cu₃O _x (YBCO) superconducting thick films have been fabricated on Cu substrates, using a simple screen-printing method from Cu-free powders (Y₂O₃ and BaCO₃). However, such films have poor superconducting properties such as critical current density (J _c) due to the low film density. In this work, we investigate the effect of uniaxial c-axis pressure on the superconducting properties of these YBCO films using a spark plasma sintering (SPS) technique. The film screen-printed on Cu substrates was heat-treated at 850°C for 5 min in vacuum varying the pressure (15, 30, and 45 MPa). To form a superconducting YBCO phase, the film was reheat-treated at 930°C for 30 s in air followed by oxygen annealing at 450°C for 1 h. For heat-treatments performed under pressure, lower film porosity was obtained, and a higher crack density was also observed compared to films prepared without pressure. The densification of the YBCO thick films using the SPS technique was very effective in improving the superconducting properties of the films.     

Study of high-quality epitaxial YBCO thin films grown directly on Y-Cut LiNbO3

Pulsed laser deposition was used to deposit high-quality YBa₂Cu₃O_7-δ (YBCO) thin films directly on y-cut LiNbO₃ substrates. The as-deposited YBCO films had a high degree of in-plane orientation and showed superconducting transition temperature (T_co) at 91K with a transition width of less than IK. Transport critical current densities were found to be ∼10⁶ A/cm² at 77K and zero field. An ion beam minimum channeling yield of 16% was obtained for YBCO films, indicating high crystallinity. High-resolution transmission electron microscopy studies showed that the interface between the film and the substrate was quite smooth and free from interfacial interdiffusion. The defects in thin films are also identified. The work showed that high-quality high T_c thin films can be deposited directly on LiNbO₃. Novel devices based on the properties of both YBCO and LiNbO₃ could be realized based on these results.     

高温超导YBCO薄膜及其制备

概述了高温超导YBCO(Y1Ba2Cu3O7-x)薄膜的基本性质、应用及制备技术的发展。介绍了脉冲激光沉积(PLD)与磁控溅射(MS)等的基本原理、工艺特点和最新发展情况。YBCO薄膜应用于超导电子器件中表现出优良的性能,如超导量子干涉仪(SQUID)等。     

Growth orientation and superconducting properties of YBa2Cu3OT-8 films prepared by the low-fluorine sol-gel process

YBa2Cu3O7-δ(YBCO) films were deposited on (100)-oriented LaAlO3 (LAO) single crystal substrates by the dip-coating process using low-fluorine solution. Their microstructures were characterized with the aid of X-ray diffractometry, scanning electron microscopy and high-resolution transmission electron microscopy. Their supercon-ducting properties were measured by the standard four-probe method. The experiment results show that the film obtained under high enough humidity conditions exhibits better c-axis texture and superconducting properties than the film under a relatively low humidity conditions. Based on the classical nucleation and chemical reaction thermodynamics theory, the underlying crystalline and growth mechanisms of YBCO films under certain humidity conditions are explained in combination with our experimental results. It is suggested that the unreacted intermediate phases such as BaF2 and CuO aggregated in the YBCO grain boundary will cause lattice distortion in the YBCO matrix and further induce the formation of a-axis oriented YBCO grains as crystallization proceeds. Therefore, it is believed that the relative content of water vapor within the heat-treatment atmosphere plays quite an important role in the preparation of c-axis oriented YBCO film with good superconducting properties.     

Propagation characteristics of high-Tc superconductinginterconnect for VLSI packaging predicted by a generalized two-fluidmodel

A generalized two-fluid model is used to analyze the propagation characteristics of high-Tc superconducting interconnects for very large scale integration (VLSI) packaging. The comparisons for surface impedance of YBa₂Cu₃O_7-x (YBCO) single crystals and thin films show data are in good agreement with the generalized two-fluid model. Based on the generalized two-fluid model, the temperature- and frequency-dependences of the attenuation constant are calculated, the transient responses of a pulse transmitted on a high-Tc superconducting interconnect are simulated, and a simple semi-empirical expression for rise time is given. The results based on the generalized two-fluid model predict an optimum operation temperature range for YBCO interconnect near at liquid nitrogen temperature