脉冲激光淀积高电流密度的YBCO超导带材

采用脉冲激光加辅助离子源的方法在长为６．０ｃｍ的ＮｉＣｒ合金基带上制备０．１３μｍ厚的Ｙ－ＺｒＯ２（ＹＳＺ）隔离层，再用脉冲激光在ＹＳＺ／ＮｉＣｒ带上制备１．５μｍ厚的ＹＢａ２Ｃｕ３Ｏ７－ｘ超导厚膜形成ＹＢＣＯ／ＹＳＺ／ＮｉＣｒ超导带材。实验测得在７７Ｋ，０Ｔｅｓｌａ下其临界电流密度为８．７５×１０４Ａ／ｃｍ２，超导转变温度为８８．６Ｋ。     

高T_cPTC陶瓷材料的配方研究

选用国产原材料，在（Ｂａ０．３Ｐｂ０．７）ＴｉＯ３＋４％ＡＳＴ＋０．０８％Ｍｎ（ＮＯ３）２材料中，添加（０．２～０．４）％（Ｎｂ２Ｏ５＋Ｙ２Ｏ３）＋０．２％ＢＮ＋（３～５）％ＣａＴｉＯ３（全为摩尔比）。采用传统陶瓷工艺，经１１５０℃适当烧结，可获得ρ２５ｃ≤１０４Ω·ｃｍ，Ｔｃ≥３８０℃，ρｍａｘ／ρｍｉｎ≥１０３，Ｖｂ≥６５０Ｖ的实用高ＴｃＰＴＣ陶瓷材料。     

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。     

用光学光谱分析仪测量准分子激光等离子体的空间角分布

本文用光学光谱分析仪（ＯＳＡ，ＷＰ－４）首次测量了ＸｅＣｌ准分子激光在ＹＢａ２Ｃｕ３Ｏ７－ｘ超导靶面激励等离子体发射谱的轴向、径向分布。综合空间分辩率＜３００μｍ。结果表明在入射激光功率密度为２．２４×１０８Ｗ／ｃｍ２，背景氧压为２×１０－１Ｔｏｒｒ时，等离子体激发态粒子具有ＣＯＳ（ｎ）θ的空间角分布。其中，ｎ的值为２．９到４．８之间。     

实现多层混合刻蚀薄膜大面积均匀的方法浅探

采用多层光刻工艺结合氩离子铣的混合刻蚀方法，刻蚀高Ｔｃ超导ＹＢａＣｕＯ／ＺｒＯ２（１００）薄膜图形，取得了较好的结果。在进行氩离子镜的工艺步骤中，使用普通氩离子铣设备（离子束斑极不均匀），但采取了一定的措施─－使被刻样品在刻蚀台座上可移动，模糊地实现了薄膜的相对＂大面积＂（直径φ≥２０ｍｍ）均匀刻蚀─－可同时刻蚀２～３片６ｍｍ×１０ｍｍ薄膜，并且被刻蚀部分表面起伏约在１０ｎｍ左右。图形样品的最小线条达２μｍ，其Ｔｃ、Ｊｃ人与刻蚀前薄膜的Ｔｃ、Ｊｃ相当，即：ＴＣ为８５～９０Ｋ，Ｊｃ～１０６Ａ／ｃｍ２（在７７Ｋ下）。     

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。     

SBT铁电薄膜及其脉冲准分子激光制备

采用脉冲准分子激光沉积法在Ｐｔ／Ｔｉ／ＳｉＯ２／Ｓｉ衬底上成功地制备了ＳＢＴ铁电薄膜，发现存在一个最佳沉积衬底温度约为４５０℃。在该温度下沉积的ＳＢＴ薄膜具有较饱和的方形电滞回线，其剩余极化Ｐｒ和矫顽电场Ｅｃ分别为８．４μＣ／ｃｍ２和５７ｋＶ／ｃｍ。     

高速集成电路中高温超导连线技术研究

本文研究了ＹＢＣＯ高温超导薄膜中原位溅射法生长优质膜的成膜技术，ＹＢＣＯ薄膜的Ｔｃｏ为９０Ｋ，Ｊｃｏ（７７Ｋ）为１０＾６Ａ／ｃｍ＾２；并建立了直流磁控溅射淀积速率的模型，还研究了微细加工形成超导薄膜导线的薄膜成形技术，在ＥＤＴＡ腐蚀法中，Ｔｃｏ仅下降１Ｋ，对超导特性影响下，本文着重研究了超导导线与高速集成电路的连续工艺，研制成功用高温超导连线的ＨＣＭＯＳ集成电路。     

单片六声道DAC PCM1600Y在多声道解码系统中的应用

１ＰＣＭ１６００Ｙ的主要特性ＰＣＭ１６００Ｙ是美国Ｂｕｒｒ－Ｂｒｏｗｎ公司于１９９９年１０月正式宣布推出的高性能单片六声道音频ＤＡＣ,广泛用于Ａ级ＤＯＬＢＹ－ＤＩＧＩＴＡＬ解码器、ＤＴＳ解码器、数字ＡＶ功放、带ＡＣ－３,ＤＴＳ,ＭＰＥＧ多声道音频解码的ＤＶＤ、ＤＶＢ等领域。ＰＣＭ１６００Ｙ的主要特性包括：２４ｂｉｔ分辨率可接受１６／１８／２０／２４ｂｉｔ字长的输入音频数据动态性能优异（Ｖ_ｃｃ＝５Ｖ时）动态范围ＤＲ：１０５ｄＢ（典型值）信噪比ＳＮＲ：１０５ｄＢ（典型值）ＴＨＤ＋Ｎ：０．００１５％…     

高导电性BaRuO_3薄膜及其脉冲激光沉积

钌酸盐是典型的ＡＢＯ３型过渡金属氧化物，具有金属导电性，其薄膜可作为电极材料用于集成铁电等器件中。分析了ＢａＲｕＯ３的钙钛矿晶体结构和导电机制，并利用ＡｒＦ准分子脉冲激光沉积（ＰＬＤ）技术，结合后续退火处理，在Ｓｉ（１００）衬底上生长出具有（１１０）取向、室温电阻率约１０－２～１０－３Ω·ｃｍ的ＢａＲｕＯ３高导电性薄膜，俄歇能谱（ＡＥＳ）和Ｒｕｔｈｅｒｆｏｒｄ背散射谱（ＲＢＳ）分析表明：薄膜ＢａＲｕＯ３的纯度高、成分均匀性好，ＢａＲｕＯ３／Ｓｉ界面存在扩散过渡层。     

Fabrication of YBCO Coated Conductors on Biaxial Textured Metal Substrate by All-Sputtering

CeO2/YSZ/CeO2 buffer layers were prepared on biaxial textured Ni-5at.%W substrate by direct-current magnetron reactive sputtering with the optimum process. YBCO thin films were deposited on CeO2/YSZ/CeO2 buffered Ni-5at.%W substrate at temperature ranging from 500℃ to 700℃ by diode de sputtering. By optimizing substrate temperature, pure c-axis oriented YBCO films were obtained. The mierostruetures of CeO2/YSZ/CeO2 buffer layers were characterized by X-ray diffraction. A smooth, dense and crack-free surface morphology was observed with scanning electron microscopy. The critical current density Jc about 0.75 MA/cm2 at 77 K was obtained.     

Sensitivity of Rs-measurement of HTS thin films by threeprime resonant techniques: cavity resonator, dielectric resonator, andmicrostrip resonator

The microwave surface resistance, R_s measurement of YBa ₂Cu₃0_{7 -δ} (YBCO) thin film deposited on 10 mm × 10 mm LaAlO₃ substrate using three prime resonating techniques, namely, cavity end plate substitution technique (20 GHz), dielectric resonator technique (18 GHz), and microstrip resonator technique (5 GHz), is reported. In addition, theoretical analysis for each technique has been performed to calculate the relative percentage error in the measured R_s -value of the YBCO thin film as a function of temperature. It has been found that the shielded dielectric resonator provides far better sensitivity for R.-measurement of the YBCO thin film with minimum relative percentage error (<4%) in the temperature range from 20 K to transition temperature of YBCO thin film compared to the other two techniques     

Critical current characteristics of YBa2Cu3O7 thin films on (110) SrTiO3

The material and electrical characteristics of YBa₂Cu ₃O₇ (YBCO) thin films deposited by inverted cylindrical magnetron sputtering on (110) SrTiO₃ (STO) were investigated. X-ray diffractometry shows the grain orientations to be predominantly the YBCO (110) and (103) with no evidence of c-axis grains, Electron micrographs show the film surface to consist of coupled elongated grains parallel to the (110) STO edge. The films were patterned into small 2.5 mm squares parallel to the substrate edges for electrical characterization. Transport currents parallel and perpendicular to the (110) substrate edge showed a 945:1 anisotropy in film resistance and a factor of two in critical current density for temperatures below 60% of the transition temperature (T_c). The temperature dependence of the critical current near T_c was quadratic-like and strongly dependent on the value of T_c used in the analysis. For the two orientations, there was nearly a 6 K difference in T_c as determined by the point at which the critical current became zero. The response of the critical current to small magnetic fields was greater for transport current along the c-axis direction and was observable over a temperature interval nearly four times greater than for current along the basal plain. These YBCO thin films have good response to small magnetic fields and are suitable for vortex flow device development     

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     

Thin film Y-Ba-Cu-O/Ag composites for fluxonic devices

We have investigated thin film composites of YBa₂Cu₃O₇ (YBCO) with Ag for fluxonic device applications. YBCO/Ag composite films are produced by first depositing a layer of Ag onto a substrate and then heating the film to the YBCO deposition temperature of 680°C or higher. YBCO is deposited by off-axis sputtering onto the Ag-coated substrate. The resulting YBCO/Ag film is a composite of YBCO with well-defined Ag regions several microns in size. Scanning electron micrograph images of the films' surfaces show a background of smooth YBCO grains dotted with Ag clusters. For a wide range of increasing Ag composition, the transition temperatures of the composite films on SrTiO₃ remain high, while the critical current densities have been reduced as much as 65 times. On MgO substrates, critical current density has been reduced by more than four orders of magnitude. Also on MgO, significant voltage response is seen in external magnetic fields of less than 1 mT. These measurements suggest that the films may be arrays of superconductor-normal-superconductor (SNS) junctions formed by weakly coupled YBCO grains with Ag in the grain boundaries. The field responsivity and low critical current densities of these composites make them potentially useful for fabrication of fluxonic devices     

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.     

Critical current density of Na doped YBCO thin films

Superconducting Y-Ba-Cu-O (YBCO) and Y-Ba-Na-Cu-O thin films were deposited on MgO substrate using a resistive evaporation technique. BaF₂ and NaF powder were used as source materials for Ba and Na elements, respectively, and pure small grains for the Y and Cu elements. In situ heat treatment has been carried out at low oxygen partial pressure. The critical current density of Na doped YBCO film was measured to be significantly higher than that of pure YBCO film.     

Synthesis and characterization of Pb(Zr0.54Ti0.46)O3 thin films on (100)Si using textured YBa2Cu3O7−δ and yttria-stabilized zirconia buffer layers by laser physical vapor deposition technique

We have fabricated high-quality <001> textured Pb(Zr_0.54Ti_0.46)O₃ (PZT) thin films on (00l)Si with interposing <001> textured YBa₂Cu₃O_7−δ (YBCO) and yttria-stabilized zirconia (YSZ) buffer layers using pulsed laser deposition (KrF excimer laser, λ, = 248 nm, τ = 20 nanosecs). The YBCO layer provides a seed for PZT growth and can also act as an electrode for the PZT films, whereas YSZ provides a diffusion barrier as well as a seed for the growth of YBCO films on (001)Si. These heterostructures were characterized using x-ray diffraction, high-resolution transmission electron microscopy, and Rutherford backscattering techniques. The YSZ films were deposited in oxygen ambient (∼9 × 10⁻⁴ Torr) at 775°C on (001)Si substrate having <001>YSZ // <001>Si texture. The YBCO thin films were deposited in-situ in oxygen ambient (200 mTorr) at 650°C. The temperature and oxygen ambient for the PZT deposition were optimized to be 530°C and 0.4-0.6 Torr, respectively. The laser fluence to deposit this multilayer structure was 2.5-5.0 J/cm². The <001> textured perovskite PZT films showed a dielectric constant of 800-1000, a saturation polarization of 37.81 μC/cm², remnant polarization of 24.38 μC/cm² and a coercive field of 125 kV/cm. The effects of processing parameters on microstructure and ferroelectric properties of PZT films and device implications of these structures are discussed.     

Buffer layers for high-quality epitaxial YBCO films on Si

Efforts aimed at producing device-quality YBa₂Cu₃ O_7-δ (YBCO) films on Si, which have resulted in films with properties comparable to what can be achieved with conventional oxide substrates such as SrTiO₃, are described. It is reported how epitaxial YBCO films were grown on Si(100) using an intermediate buffer layer of yttria-stabilized zirconia (YSZ). Both layers are grown with an entirely in situ process by pulsed laser deposition (PLD). Ion channeling revealed a high degree of crystalline perfection with a channeling minimum yield for Ba as low as 12%. The normal state resistivity was 250-300 μΩ-cm at 300 K; the critical temperature, Tc (R=0), was 86-88 K, with a transition width of 1 K. Critical current densities of 2×10⁷ at 4.2 K and 2.2×10⁶ at 77 K have been achieved. Noise measurements indicate that these films are suitable for use in highly sensitive far-infrared bolometers. Applications of this technology to produce in situ reaction patterned microstrip lines are discussed