共查询到20条相似文献,搜索用时 15 毫秒
1.
J. Zhao Y. Q. Li C. S. Chern W. Huang P. Norris B. Gallois B. Kear P. Lu F. Cosandey 《Journal of Electronic Materials》1991,20(4):341-343
YBa2Cu3O7-x
(YBCO) superconducting thin films with a critical current density exceeding 1 x 106 A/cm2 at 77.7 K were prepared by a plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) process. The thin films (130
nm thick) were formed in-situ on LaAlO3 substrates at a temperature of 670‡ C in 2 Torr partial pressure of activated N2O. Resistivity and magnetic susceptibility measurements of the as-deposited films show a sharp superconducting transition
temperature of 89.8 K. Critical current densities were measured by the dc transport method with a patterned bridge of 120
× 40 Μm. Both x-ray diffraction and high resolution electron microscopy measurements indicate that films grew epitaxially
with the c-axis perpendicular to the surface of the substrate. 相似文献
2.
CNx:B thin films were prepared on titanium coated ceramic substrate by pulsed laser deposition technique (PLD). The microstructure of the film was examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The analyses indicate that the deposited samples are amorphous CNx:B thin films. Field electron emission characteristics of amorphous CNx:B thin films were measured in a vacuum chamber with a base pressure of about 3.2×10−5 Pa. The turn-on field of the film was 3.5 V/μm. The current density was 60 μA/cm2 at an electric field of 9 V/μm. The experimental results indicate that this film could be a promising material applicable to cold cathodes. 相似文献
3.
A. C. Westerheim P. C. Mcintyre S. N. Basu D. Bhatt L. S. Yu-Jahnes Alfredo C. Anderson M. J. Cima 《Journal of Electronic Materials》1993,22(8):1113-1120
The surface morphology and microstructure of in situ and ex situ derived YBa2Cu3O7−x (YBCO) thin films have been investigated. In situ films were deposited by single-target off-axis sputtering and three-target
co-sputtering. Ex situ films were derived by metalorganic deposition (MOD) of trifluoroacetate precursors. Surface defects
resulting from mixed a-axis and c-axis orientation as well as secondary phases have been identified in these films. Despite
these defects, films with excellent electrical properties have been formed. However, defects interfere with film patterning
and the fabrication of multi-layered structures. Several secondary phase precipitates have been identified, including CuO,
Y2O3, Cu-Ba-O, and Y2Cu2O5. Secondary phases resulting from a lack of stoichiometry can be eliminated by direct composition control in the MOD and three-target
sputtering techniques, and by composition control through the application of an externally applied magnetic field in single-target
off-axis sputtering. Secondary phases caused by contamination were also identified: Cr-Ba-O in off-axis sputtering, resulting
from contamination by the oxidized heater block; and BaSO4 in MOD, resulting from gas phase impurities. These results suggest that cation composition control is not sufficient to prevent
the formation of secondary phases and that small levels of contamination may prevent phasepure material from being formed. 相似文献
4.
M. Silinskas M. Lisker B. Kalkofen E.P. Burte 《Materials Science in Semiconductor Processing》2006,9(6):1102
Strontium tantalate (STO) films were grown by liquid-delivery (LD) metalorganic chemical vapor deposition (MOCVD) using Sr[Ta(OEt)5(OC2H4OMe)]2 as precursor. The deposition of the films was investigated in dependence on process conditions, such as substrate temperature, pressure, and concentration of the precursor. The growth rate varied from 4 to 300 nm/h and the highest rates were observed at the higher process temperature, pressure, and concentration of the precursor. The films were annealed at temperatures ranging from 600 to 1000 °C. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and ellipsometry indicated that the as-deposited and the annealed films were uniform and amorphous and a thin (>2 nm) SiO2 interlayer was found. Crystallization took place at temperatures of about 1000 °C. Annealing at moderate temperatures was found to improve the electrical characteristics despite different film thickness (effective dielectric constant up to 40, the leakage current up to 6×10−8 A/cm2, and lowest midgap density value of 8×1010 eV−1 cm−2) and did not change the uniformity of the STO films, while annealing at higher temperatures (1000 °C) created voids in the film and enhanced the SiO2 interlayer thickness, which made the electrical properties worse. Thus, annealing temperatures of about 800 °C resulted in an optimum of the electrical properties of the STO films for gate dielectric applications. 相似文献
5.
Practical superconducting thick films and tapes, manufactured in an industrial process, have microscopic inhomogeneities.
Quantitative magneto-optical imaging (MOI) is one of the most desirable techniques and provides both local and global information
on defects, flux pinning, critical current density J
c, and current distribution. We present, herein, a comparative magneto-optical imaging study of the flux profile in YBa2Cu3O7−δ (YBCO) thick films prepared in two different processes, the laboratory versus the industrial scalable process. The remarkably
different flux propagation patterns are the manifestation of their different defect landscapes within these films. A method
of determining J
c near zero applied field is also given for locally nonuniform superconducting films, using the quantitative MOI technique. 相似文献
6.
《Applied Superconductivity》1999,6(10-12):795-798
It is possible to produce HTSC thin films of polymer metal precursors by the simple spincoating technique. This method can be used to manufacture of Y–Ba–Cu–O- and Bi–Sr–Ca–Cu–O–HTSC thin films. The microbridges are generated into the precursor film by photolithography. The etching process step is cancelled. After that the superconducting phases are formed at 950°C respectively 865°C during the tempering process. The HTSC structures serve as a previous stage for SNS contact. The critical temperatures (Tc) measured on the 20 and 200 μm wide microbridges are 82 K for Y–Ba–Cu–O and 108 K for Bi–Sr–Ca–Cu–O. The critical current density (jc) obtained is 105 A/cm2 for 65 K. 相似文献
7.
《Applied Superconductivity》1994,2(6):391-400
This study demonstrates the preparation of screen printed Bi-(Pb)-Sr-Ca-Cu-oxide superconducting films starting from a paste, based on spray dried nitrate solutions. The spray dried precursor powder was studied using TGA-DTA and XRD. It is shown that decomposition to oxides occurs at temperatures more than 200°C lower than those in the respective oxide/carbonate mixture.The thick film properties were studied using XRD, SEM-EDAX and electrical resisitivity measurements. The films, coated on alumina substrates, showed clear superconducting transition below 60K, but did not reach zero resistivity. Films coated on alumina with a ZrO2 buffer layer and sintered at 835°C showed Tc, 0 up to 77 K. 相似文献
8.
P. Tiwari X. D. Wu S. R. Foltyn R. E. Muenchausen P. N. Arendt I. H. Campbell Q. X. Jia D. E. Peterson T. E. Mitchell 《Journal of Electronic Materials》1996,25(1):131-135
Pulsed laser deposition was used to deposit high-quality YBa2Cu3O7-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
(Tco) 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 Tc 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. 相似文献
9.
10.
S.H. Wee A. Goyal J. Li Y. Zhang L. Heatherly 《Journal of Electronic Materials》2007,36(10):1230-1233
NdBa2Cu3O7−δ (NdBCO) films were grown on rolling-assisted biaxially textured substrates (RABiTS) via pulsed laser deposition. c-Axis-oriented epitaxial NdBCO films with high performance were obtained under optimal deposition conditions. Transmission
electron microscopy analysis shows that the NdBCO film grown on RABiTS has a clear interface with a CeO2 cap layer and a nearly perfect lattice structure. The NdBCO film exhibits higher T
c of 93.7 K and better in-field J
c in magnetic fields and at all field orientations, compared to pure YBCO films. 相似文献
11.
B. Lee A. Hande R.M. Wallace Y. Senzaki H. Li J. Suydam 《Microelectronic Engineering》2009,86(3):272-276
ZrO2 thin films were deposited by the atomic layer deposition process on Si substrates using tetrakis(N,N′-dimethylacetamidinate) zirconium (Zr-AMD) as a Zr precursor and H2O as an oxidizing agent. Tetrakis (ethylmethylamino) zirconium (TEMA-Zr) was also evaluated for a comparative study. Physical properties of ALD-derived ZrO2 thin films were studied using ellipsometry, grazing incidence XRD (GI-XRD), high resolution TEM (HRTEM), and atomic force microscopy (AFM). The ZrO2 deposited using Zr-AMD showed a better thermal stability at high substrate temperature (>300 °C) compared to that using TEMA-Zr. GI-XRD analysis reveals that after 700 °C anneal both ZrO2 films enter tetragonal phase. The electrical properties of N2-annealed ZrO2 film using Zr-AMD exhibit an EOT of 1.2 nm with leakage current density as low as 2 × 10−3 A/cm2 (@Vfb−1 V). The new Zr amidinate is a promising ALD precursor for high-k dielectric applications. 相似文献
12.
S. K. Chen A. Serquis G. Serrano K. A. Yates M. G. Blamire D. Guthrie J. Cooper H. Wang S. Margadonna J. L. MacManus‐Driscoll 《Advanced functional materials》2008,18(1):113-120
By applying a combination of characterisation tools, changes in structural and superconducting properties with nominal Mg non‐stoichiometry in MgxB2 are found. The non‐stoichiometry produces enhanced in‐field critical current densities (Jc's) and upper critical field / irreversibility field (Hc2/Hirr(T)) values. Upper critical fields of ~ 21 T (4.2 K) were obtained in nominal Mg‐deficient samples compared to ~ 17 T (4.2 K) for near‐stoichiometric samples. 相似文献
13.
E Atanassova D SpassovA Paskaleva J KoprinarovaM Georgieva 《Microelectronics Journal》2002,33(11):907-920
The effect of the oxidation temperature (673-873 K) on the microstructural and electrical properties of thermal Ta2O5 thin films on Si has been studied. Auger electron spectroscopy and X-ray photoelectron spectroscopy results revealed that the films are non-stoichiometric in the depth; an interfacial transition layer between tantalum oxide and Si substrate, containing presumably SiO2 was detected. It has been found by X-ray diffraction that the amorphous state of Ta2O5 depends on both the oxidation temperature and the thickness of the films—the combination of high oxidation temperature (>823 K) and thickness smaller than 50 nm is critical for the appearance of a crystal phase. The Ta2O5 layers crystallize to the monoclinic phase and the temperature of the phase transition is between 773 and 823 K for the thinner layers (<50 nm) and very close to 873 K for the thicker ones. The electrical characterization (current/voltage; capacitance/voltage) reveals that the optimal oxidation temperature for achieving the highest dielectric constant (∼32) and the lowest leakage current (10−8 A/cm2 at 1 MV/cm applied field) is 873 K. The results imply that the poor oxidation related defects are rather the dominant factor in the leakage current than the crystallization effects. 相似文献
14.
D. Kumar R. D. Vispute O. Aboelfotoh S. Oktyabrsky K. Jagannadham J. Narayan P. R. Apte R. Pinto 《Journal of Electronic Materials》1996,25(11):1760-1766
Metallization of high-Tc superconductors using low resistivity metal oxides and Cu-Ge alloys has been investigated on high quality pulsed laser deposited
epitaxial YBa2Cu3O7-x (YBCO) films. Epitaxial LaNiO3 (LNO) thin films have been grown on YBCO films at 700°C using pulsed laser deposition. The specific resistivity of LNO was
measured to be 50 μΩ-cm at 300K which decreases to 19 μΩ-cm at 100K indicating good metallicity of the LNO films. The contact
resistance of LNO-YBCO thin film interface was found to be reasonably low (of the order of 10-4Ω-cm2 at 77K) which suggests that the interface formed between the two films is quite clean and LNO can emerge as a promising metal
electrode-material to YBCO films. A preliminary investigation related to the compatibility of Cu3Ge alloy as a contact metallization material to YBCO films is discussed. The usage of other oxide based low resistivity materials
such as SrRuO3 (SRO) and SrVO3 (SVO) for metallization of high-Tc YBCO superconductor films is also discussed. 相似文献
15.
《Applied Superconductivity》1999,6(6):267-278
We present a grain microstructure for Bi(2212) consisting of only giant needle-shaped grains of around 1.5 mm length and 100 μm diameter. We study the structural and chemical changes suffered by a conventional ceramic Bi(2212) sample in the course of the thermal treatment used to obtain those giant needle-shaped grains. For that, different samples of the same batch were treated with incomplete thermal treatments, and the resulting samples were analysed by using scanning electron microscopy (SEM), optical microscopy, energy dispersed spectroscopy (EDS), inductively coupled plasma (ICP) and X-ray diffraction (XRD). To verify the superconducting nature of the needle-shaped grains, we have performed magnetization, resistivity, and critical current measurements on the original ceramic sample, and on that formed as giant needle-like grains. The critical temperature of these last grains is nearly the same as that of the ceramic sample (Tc∼90 K), which is a high value for the Bi(2212) compound. The critical current density (Jc) of the needle-shaped grains is around 2500 A/cm2 at 77 K and in absence of applied magnetic field, a value comparable with that presented for the best wires and thick films. Not only are the shape and the size of these grains very suitable for making superconducting wires, but also the superconducting properties, Tc and Jc, are both high enough to be confident about the possibility of improving the actual Bi(2212) superconducting wires for high current applications. 相似文献
16.
《Applied Superconductivity》1996,4(1-2):111-117
SmBa2SbO6 has been synthesized and sintered as a single phase material for its use as a subtrate for YBa2Cu3O7−δ superconducting thick films. Superconducting YBa2Cu3O7 −δ and YBa2Cu3O7−δ-Ag thick films were fabricated by dip coating on SmBa2SbO6 and a zero resistivity superconducting transition Tc(0) = 92 K was obtained for both thick films. The YBa2Cu3O7−δ and YBa2Cu3O7−δ-Ag thick films gave a critical current of 2 x 103 A/cm2 and 3 x 104 A/cm2, respectively, at 77 K. YBa2Cu3O7−δ-Ag film showed substantial (001) orientation on the substrate. The superconducting films were highly stable under atmospheric conditions. 相似文献
17.
P. A. Zawadzki G. S. Tompa P. E. Norris C. S. Chern R. Caracciolo B. H. Kear D. W. Noh B. Gallois 《Journal of Electronic Materials》1990,19(4):357-362
The discovery of YBCO superconductors has stimulated a great deal of scientific and technological research into thin films
of these materials. Because the MOCVD technique is known to produce high quality films in the III/V and II/VI material groups,
our approach has been to apply the method to superconducting thin films. Thin films were grown in a vertical high speed (0–2000
rpm) rotating disk reactor. The source materials were metalβ-diketonates kept at temperatures in excess of 100° in order to obtain growth rates of 0.3 to 0.5μm/hr. The precursors were transported to the chamber with a nitrogen carrier and injected separately in order to avoid any
gas phase reactions. The chamber pressure was maintained at 76 Torr with an oxygen partial pressure of 38 Torr. A resistance
heater was used to keep the substrate temperature at 500° YBa2Cu3O7-x
films were deposited simultaneously on a variety of substrates such as (100) MgO, (1-102) sapphire, (100) SrTiO3 and (100) YSZ. Full XPS spectra were collected for the binary oxides. The scans demonstrate the existence of Y2O3, BaO, and CuO with the correct valence state for the metallic species. Energy dispersive analysis of x-ray (EDAX) was used
to determine film compositions by comparing EDAX spectral intensity to a known superconducting standard. Appropriate changes
were made in the precursor flows to correct the stoichiometry. The as-grown films were dark brown and semi-transparent. Cross-sectional
SEM photomicrographs revealed an ordered columnar structure. After annealing at 950–980° however, the films on (100) SrTiO3 appeared dull black and opaque. The surface morphology exhibited smooth large plate-like grains. X-ray data clearly display
an orthorhombic phase, with c-axis perpendicular to the substrate surface. Four point resistance measurements for films on
(100) SrTiO3 show the onset of superconductivity at 90 K with a complete loss of resistance at 88 K. This sharp (≤2K) transition shows
the high quality of these MOCVD grown YBCO films and are the first reported results from a large area (2 × 50 mm substrates)
commercial reactor. 相似文献
18.
采用水热法和电化学沉积法,成功制备了包覆有SnO2纳米颗粒的WO3纳米棒阵列薄膜,退火处理后形成WO3/SnO2异质结复合薄膜。通过改变SnO2的沉积时间得到了复合薄膜的最佳制备条件。采用XRD,FESEM对WO3/SnO2复合薄膜的物相和形貌进行了分析,通过电化学工作站对WO3/SnO2复合薄膜的光电性能进行了研究,结果表明,电沉积时间为120 s时,WO3/SnO2复合薄膜具有最小的阻抗,且在0.6 V的偏压下光电流密度为0.46 mA/cm2,相比于单一WO3纳米棒薄膜,表现出更好的光电化学性能。 相似文献
19.
W. M. Huber T. Veit P. G. Huggard W. Prettl 《Journal of Infrared, Millimeter and Terahertz Waves》1995,16(10):1757-1768
YBa2Cu3O7-δ thin films may be epitaxially grown, on suitably prepared substrates, with a non-zero tilt angle between the film's c-axis and its surface normal. These films are fast, room-temperature, thermoelectric detectors with a response extending from UV to FIR wavelengths. We have found that tilted c-axis films, when cooled below Tc, also exhibit a fast and sensitive Josphson photoresponse to 250 µm and 496 µm radiation, in contrast to the nil response of c-axis normal films. It is believed that the non-zero component of the radiation electric field along the c-axis of tilted films modulates relatively weak Josephson critical currents in this direction, generating a photoresponse from current biased samples. 相似文献
20.
《Applied Superconductivity》1996,4(10-11):435-446
For high-current applications, homogeneous well-textured high-temperature superconducting Y1Ba2Cu3O7−δ (Y-123) films on technical ceramic or metallic substrates are required. The ion-beam-assisted deposition (IBAD) of yttria-stabilized zirconia (YSZ) buffer layers, which serve as a template for Y-123, was extended to large-area substrates as well as differently shaped long substrates. TEM, as well as XRD investigations, was performed to observe the relevant growth mechanisms. The influence of nucleation, growth selection, and homoepitaxial growth on the development or the maintenance of a preferential orientation of the YSZ buffer is discussed. Y-123 films were prepared by a modified pulsed-laser-deposition (PLD) technique based on a quasi-equilibrium substrate heating and variable azimuth scanning of the target. The method allows a PLD coating of long pieces of tapes and tubular substrates because no direct mechanical contact of a substrate with the heater is required. Critical current densities, Jc, above 106 A cm−2 were achieved on polycrystalline Ni tapes as well as on polycrystalline YSZ sheets at 77 K and self fields. The dependence of Jc on magnetic field resembles that of Y-123 deposited on single-crystalline substrates and demonstrates the absence of weak links due to grain boundaries. The thickness dependence of Jc is interpreted in terms of a nucleation layer appearing in the early stage of film growth. A growth model is proposed which seems to be in agreement with the experimental observations. The measured strain tolerance of the films does not impede their application. 相似文献