Phase Transformation and Optimized Growth of TFA-MOD REBa_2Cu_3O_(7-x) Films for Coated Conductors

Several types of REBa2Cu3O7-x (REBCO, RE=Y, Ho etc.) films are prepared on single crystal substrate LaAlO3 by TFA-MOD method. The phase transformation and optimized growth conditions in the crystallization are studied. Compared with SmBCO and GdBCO, high quality YBCO and HoBCO films are relatively easy to produce. It is revealed that the YBCO grains can form at low temperatures such as 730 °C during the initial heating ramp. With a high heating rate of 20 K/min and a low oxygen pressure of 100 ppm, the opti...     

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.     

Dielectric Characteristics of Ba0.65Sr0.35TiO3 Thin Films by Sol-Gel Method

Ferroelectric Ba0.65Sr0.35TiO3 (BST) thin films on the Pt/Ti/SiO2/Si substrate have been successfully prepared by sol-gel. Such films have approximately 300 nm thicknesses with a remnant polarization of about 2.95 C/cm2 and a coercive field of about 21.5 kV/cm. The investigations of X-ray diffraction and atomic force microscopy show that the BST films annealed at 650 ℃ exhibit a tetragonal structure and that the films dominantly consist of large column or grains of about 89 nm in diameter. The curves of the temperature dependence of dielectric coefficient in different frequencies display the curie transition at the temperature around 23 ℃. The dielectric loss tangent of BST thin films at 100 kHz is less than 0.04. As a result, the BST thin films are more applicable for fabrication of infrared detector compared with the BST thin films reported previously.     

Effect of substrate temperature on the properties of deep ultraviolet transparent conductive ITO/Ga2O3 films

正ITO/Ga_2O_3 bi-layer films were deposited on quartz glass substrates by magnetron sputtering.The effect of substrate temperature on the structure,surface morphology,optical and electrical properties of ITO/Ga_2O_3 films was investigated by an X-ray diffractometer,a scanning electron microscope,a double beam spectrophotometer and the Hall system,respectively.The structural characteristics showed a dependence on substrate temperature. The resistivity of the films varied from 6.71×10~(-3) to 1.91×10~3Ω·cm as the substrate temperature increased from 100 to 350℃.ITO(22 nm)/Ga_2O_3(50 nm) films deposited at 300℃exhibited a low sheet resistance of 373.3Ω/□and high deep ultraviolet transmittance of 78.97%at the wavelength of 300 nm.     

Effects of Heat Treatment on Thermoelectric and Infrared Properties of Bi2Te3 Films

In this work, Bi2Te3 films (250 nm) are fabricated on SiO2/Si substrates by radio frequency (RF) magnetron sputtering at room temperature, and the prepared films are annealed over the temperature range of 200 ℃ to 400 ℃. Crystallinity and electrical properties of the films can be tuned correspondingly. The power factors of Bi2Te3 films of 0.85 W/K2cm to 11.43 W/K2cm were achieved after annealing. The infrared reflectance measurements from 2.5 m to 5.0 m demonstrate that there is also a slight red-shift of the plasma oscillation frequency in the Bi2Te3 films. By means of plasmonic calculations, we attribute the red-shift of absorption peaks to the reduction of carrier concentration and the change of effective mass of Bi2Te3 films with the increased annealing temperature.     

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     

Liquid phase epitaxy for the production of YBa2Cu3O7-δ coated conductor

The liquid phase epitaxy (LPE), which is performed under ambient pressure with simple growth apparatus, allows us to fabricate high-Jc YBa₂Cu₃O_7-δ (YBCO) crystalline thick films at high growth rate. We propose that the LPE growth of YBCO films on single crystalline oxide fibers is another way to produce YBCO-coated conductors for power application. In the conventional case of using BaO–CuO melt as a solvent, by which the YBCO crystals grow at about 1000°C, YBCO coating on yttria-stabilized zirconia (YSZ) or SrTiO₃ (STO) single crystalline fibers has not been successfully achieved because of their reaction with the solvent. Recently we have discovered that BaF₂ added as a solution decreases the crystallization temperature of YBCO down to 900°C and suppress the reactivity with no degradation of superconductivity of the YBCO crystal. The YBCO-coated fibers are successfully prepared using this solution. The behavior of critical current under magnetic fields shows that these YBCO-coated fibers have the potential to be used under a high magnetic field at the temperature of liquid nitrogen.     

PbO和Bi_2O_3-Li_2CO_3助烧剂对Pb(Zr_(0.9)Ti_(0.1))O_3厚膜热释电性能的影响

采用丝网印刷工艺制备了Pb(Zr0.9T0.1)O3(PZT)厚膜,研究了过量PbO和Bi2O3-Li2CO3共同助烧对PZT厚膜低温烧结特性、微观结构、相构成以及介电和热释电性能的影响。结果表明:随着过量PbO及Bi2O3-Li2CO3添加量的增加,PZT厚膜的烧结温度和晶粒尺寸均逐渐降低。当PbO过量6.4%(质量分数)、Bi2O3-Li2CO3添加量为5.4%(质量分数)时,PZT厚膜可在900℃低温下致密成瓷,且其热释电系数和探测率优值均得到大幅提高;所得样品在30℃时的热释电系数为10.6×10–8C.cm–2.K–1,探测率优值为8.2×10–5Pa–1/2。     

Coaxial line configuration for microwave power transmission studyof YBa2Cu3O7-δ thin films

Microwave transmission measurements through YBa₂Cu₃O_7-δ (YBCO) high-transition-temperature superconducting thin films on lanthanum aluminate (LaAlO₃) have been performed in a coaxial line at 10 GHz. LaAlO₃ substrates were ultrasonically machined into washer-shaped discs, polished, and coated with laser-ablated YBCO. These samples were mounted in a 50-Ω coaxial air line to form a short circuit. The power transmitted through the films as a function of temperature was used to calculate the normal state conductivity and the magnetic penetration depth for the films     

Zn0.8Na0.1Co0.1O薄膜的制备及衬底温度对其影响

采用脉冲激光沉积(PLD)技术.在温度为400、500和600℃的SiO2衬底上成功制备出Zn0.8Nao.1Co0.1O薄膜.用x射线衍射(XRD)、原子力显微镜(AFM)、荧光光谱仪、四探针电阻率测试台等对薄膜的结构、表面形貌和光电性质进行了表征,讨论了不同衬底温度对薄膜结构、光学和电学性质的影响.结果表明:掺杂没...     

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     

The coplanar resonator technique for determining the surfaceimpedance of YBa2Cu3O7-δ thinfilms

We describe how coplanar microwave resonators fabricated from patterned thin films of YBa₂Cu₃O₇(-δ) (YBCO) can he used to measure the ab-plane microwave surface impedance Z_s=R_s+jX_s of the films, in particular the absolute value and temperature dependence of the magnetic penetration depth λ. The current distribution of the resonator is calculated by modelling the resonator as a network of coupled transmission lines of rectangular cross-sections; this is then used to estimate the ab-plane λ(T) from the measurements of resonators of different geometries patterned onto the same film. We obtain values of λ(0) in the range 150-220 nm. The unloaded quality factors of the linear resonators at 7.95 GHz are around 45000 at 15 K and around 6500 at 77 K. We estimate the corresponding values of the intrinsic R_s at 7.95 GHz to be 23 μΩ and 110 μΩ at 15 K and 77 K, respectively. These values are comparable with those of other high quality unpatterned YBCO films reported in the literature. Z_s for the best optimised films appears to be insensitive to the effects of patterning     

脉冲激光外延生长YBa2Cu3O7–δ涂层导体LaMnO3缓冲层

采用脉冲激光沉积技术在双轴织构的Ni95W5(Ni-5W)合金基底上外延生长了LaMnO3(LMO)薄膜作为涂层导体缓冲层,研究了沉积温度对LMO薄膜生长织构和表面形貌的影响。研究结果表明：沉积温度对LMO薄膜的表面形貌有一定的影响;在沉积温度为650 ℃时,LMO薄膜具有良好的(00l)取向,薄膜表面平整均匀,光滑致密,其均方根粗糙度在2 nm以下;而且,在此LMO缓冲层上外延生长的YBa2Cu3O7–δ超导层具有良好的双轴织构,超导转变温度Tc为92 K,转变宽度小于1 K,临界电流密度Jc为5.3×105 A/cm2(77 K,自场)。     

原子层沉积方法制备低温多层Al2O3/TiO2复合封装薄膜的研究

原子层沉积(ALD)方法可以制备出高质量薄膜,被认为是可应用于柔性有机电致发光器件(OLED)最有发展前景的薄膜封装技术之一。本文采用原子层沉积(ALD)技术,在低温(80℃)下,研究了Al₂O₃及TiO₂薄膜的生长规律,通过钙膜水汽透过率(WVTR)、薄膜接触角测试等手段,研究了不同堆叠结构的多层Al₂O₃/TiO₂复合封装薄膜的水汽阻隔特性,其中5 nm/5 nm×8 dyads(重复堆叠次数)的Al₂O₃/TiO₂叠层结构薄膜的WVTR达到2.1×10^-5 g/m²/day。采用优化后的Al₂O₃/TiO₂叠层结构薄膜对OLED器件进行封装,实验发现封装后的OLED器件在高温高湿条件下展现了较好的寿命特性。     

Anomalous microwave response ofYBa2Cu3O7-δ granular thin filmsunder magnetic fields

The microwave response of YBa₂Cu₃O_7-δ (YBCO) granular films has been studied at a microwave frequency of 30.5 GHz. In absence of a magnetic field, the dependencies of a normal microwave response on the bias current was observed at a temperature close to T_c. When a magnetic field ranging from 5.0 to 33.0 mT is applied, the responses broaden and shift toward a lower temperature. In the superconducting state, the responses were found to be highly dependent on the magnetic field. For a current of 5.0 mA and a magnetic field above 17.0 mT, the responses increased and did not vanish, even at a very low temperature, which is believed to be correlative with the anisotropic character of the structure     

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.     

二氧化锡覆盖层对ITO透明导电薄膜热稳定性的改良

采用射频磁控溅射法在ITO玻璃表面沉积了一层15 nm左右的SnO2薄膜。利用霍尔效应测试仪、四探针电阻测试仪、场发射电子显微镜及紫外–可见–近红外光谱仪分析了所制薄膜的电学性质、表面形貌和光学性质。结果表明,在300~600℃退火后镀有SnO2覆盖层的ITO(SnO2/ITO)薄膜具有相对好的热学稳定性。在600℃退火后,ITO薄膜的方阻和电阻率分别为88.3Ω/□和2.5×10–3.cm,而此时,SnO2/ITO薄膜的方阻和电阻率仅为43.8Ω/□和1.2×10–3Ω.cm。最后,阐述了SnO2覆盖层提高ITO薄膜热稳定性的机制。     

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。     

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     

Microwave properties of epitaxial large-area Ca-doped YBa2Cu3O7−δ thin films on r-plane sapphire

Ca doping of YBa₂Cu₃O_7−δ (YBCO) is well known to enhance the critical current density in large-angle grain boundaries for example of bicrystals. However, up to now no data are available on microwave properties of epitaxial Ca-doped YBa₂Cu₃O_7−δ thin films on r-plane sapphire with CeO₂ buffer layer.Therefore, first results are presented for large-area pulsed laser deposition (PLD) grown Ca_xY_1−xBa₂Cu₃O_7−δ films on 3-in. diameter sapphire wafers. The PLD process is optimised for undoped YBCO thin films and shows high reproducibility for YBCO. The microwave surface resistance R_s at 8.5 GHz of Ca-doped YBCO (x=0.1) thin films shows clear reduction (up to 20%) with respect to that of YBCO for temperatures from about 20–50 K. In addition, microwave surface resistance R_s of Ca-doped YBCO is lower than that of YBCO even for enhanced microwave surface magnetic field up to about 20 mT for temperatures 20 and 40 K.