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1.
A study on the microwave responses of YBCO and TBCCO thin films by coplanar resonator technique
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YBa2Cu3O7(YBCO) thin films have been prepared by
thermal coevaporation on LaAlO3(LAO) substrates, and
Tl2Ba2CaCu2O8(TBCCO) thin films are synthesized
by magnetron sputtering method on LAO substrates. The transition
temperature Tc is 90\,K for YBCO/LAO and 104\,K for
TBCCO/LAO. Microwave responses of the films are studied
systematically by coplanar resonator technique. Energy gaps of the
films obtained are {\it\Delta}0=1.04kBTc for YBCO
films and ${\it\Delta}_0=0.84kBTc for TBCCO films by
analysing the temperature dependence of resonant frequencies of
coplanar resonator. Penetration depth at 0\,K \lambda 0=198nm
for YBCO films and \lambda0 =200nm for TBCCO films could also
be obtained by using the weak coupling theory and two fluid theory.
Results of penetration depth and energy gap confirm the weak coupling
properties of the films. In addition, microwave surface resistances
Rs of YBCO/LAO and TBCCO/LAO are also investigated by
analysing the quality factor and insert loss of the coplanar
resonator. Surface resistance of TBCCO/LAO is less than that of
YBCO/LAO, so that TBCCO/LAO films may have more potential
applications. 相似文献
2.
A comparative study of YBa2Cu3O7-δ/YSZ bilayer films deposited on silicon-on-insulator substrates with and without HF pretreatment
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Highly epitaxial YBa2Cu3O7-δ (YBCO) and yttria-stabilized zirconia (YSZ) bilayer thin films have been deposited on silicon-on-insulator (SOI) substrates by using in situ pulsed laser deposition (PLD) technique. In the experiment, the native amorphous SiO2 layers on some of the SOI substrates are removed by dipping them in a 10% HF solution for 15 s. Comparing several qualities of films grown on substrates with or without HF pretreatment, such as thin film crystallinity, general surface roughness, temperature dependence of resistance, surface morphology, as well as average crack spacing and crack width, naturally leads to the conclusion that preserving the native SiO2 layer on the surface of the SOI substrate can not only simplify the experimental process but can also achieve fairly high quality YSZ and YBCO thin films. 相似文献
3.
The a-axis oriented YBa2Cu3Ox(YBCO) thin films could be grown on (100) SrTiO3(STO) substrates with STO buffer layers by dc and rf magnetron sputtering either by low-ering the deposition temperature, or by using a self-template technique. For the latter, the resistivity of the thin film at 290K along the substrate [001] direction is about four times larger than that in the [010] direction. The zero resistance temperatures Tc0 are 89 K in both directions. So high quality a-axis oriented YBCO thin films can be prepared by the self-template technique. Also the Tc0 increase monotonously with the reduction of the thickness of the YBCO seed layer. 相似文献
4.
Microwave Response of MgB2/A12O3 Superconducting Thin Films by Microstrip Resonator Technique
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Double-sided superconducting MgB2 thin films are deposited onto c-A120a substrates by the hybrid physical chemical vapour deposition method. The microwave response of MgB2/A12O3 is investigated by microstrip resonator technique. A grain-size model is introduced to the theory of microstrip resonators to analyse microwave properties of the films. We obtain effective penetration depth of the films at OK (λe0 = 463nm) and surface resistance (R8 = 1.52 mΩ at 11 K and 8. 73 GHz) by analysing the resonant frequency and unload quality factor of the microstrip resonator, which suggests that the impurities and disorders of grain boundaries of MgB2/A12 Oa result in increasing penetration depth and surface resistance of the films. 相似文献
5.
Fabrication of YBCO/YSZ and YBCO/MgO thick films using electrophoretic deposition with top-seeded melt growth process
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Superconducting thick films were grown on single crystals MgO and YSZ by electrophoretic deposition with Y_2BaCuO_5(Y211) addition. YBCO thick films were then accomplished by sintering the precursor films above the peritectic temperature. Single crystals of MgO (3×3×0.5 mm^3) were used as top-seed to control crystal structure of the thick films. As shown by scanning electron microscopy, the morphologies of YBCO/YSZ and YBCO/MgO thick films are spherulitic texture and platelet type. The critical temperature is ~89 K for the YBCO/YSZ thick film; the onset transition temperature is 86.4 K and the transition width is ~3 K for YBCO/MgO thick film. The critical current densities (as determined by Bean model) are, in A/cm^2, 3870 (77 K) for YBCO/YSZ thick films and 2399 (77 K) for YBCO/MgO thick films, which are comparable to the best J_c reported of the thick films prepared by the same method. 相似文献
6.
Spectroscopic ellipsometric measurements in infrared region (2.5 - 12.5 μm) are carried out to characterize the structure and quality of diamond films grown by microwave plasma chemical vapor deposition (MPCVD) and hot filament chemical vapor deposition (HFCVD), respectively. It is found that the establishment of appropriate models has the strongest influence on the fit of ellipsometric spectra. The best fit is achieved for MPCVD film with a 77.5-nm middle layer of SiO2, and for HFCVD film with an 879-nm rough surface layer included by Bruggeman effective medium approtimation (EMA). Finally the refractive index and the extinction coefficient are calculated for both films, the results show that the film grown by MPCVD is optically much better than that grown by HFCVD at infrared wavelengths. 相似文献
7.
Effects of high temperature rapid thermal annealing on Ge films grown on Si(001) substrate
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Tensile strain,crystal quality,and surface morphology of 500 nm thick Ge films were improved after rapid thermal annealing at 900 C for a short period(20 s).The films were grown on Si(001)substrates by ultra-high vacuum chemical vapor deposition.These improvements are attributed to relaxation and defect annihilation in the Ge films.However,after prolonged(20 s)rapid thermal annealing,tensile strain and crystal quality degenerated.This phenomenon results from intensive Si–Ge mixing at high temperature. 相似文献
8.
In this study, Tungsten Oxide (WO3) thin films were prepared by Chemical Spray Pyrolysis (CSP) and Spin Coating (SC) techniques and it was investigated effects of technique and parameter on the films. WO3 thin films were deposited on ITO (Indium Tin Oxide) coated glasses. The structural, optical and electrochromic properties of the WO3 thin films were characterized by XRD, SEM, UV, and CV measurements. The sharpest (200) peak was observed in the XRD spectra and optical band gaps were calculated around 2.6~3.1 eV via UV-Vis spectra for all of the samples. Micro fibrous reticulated surface (filamentous like) morphology for the films deposited by CSP technique and smooth surface morphology with high optical transmittance for the film deposited by SC Technique were obtained from SEM images. In addition to these results, it was revealed that all the samples exhibit good electrochromic performance. 相似文献
9.
Hydrogenated microcrystalline silicon (\mu c-Si:H) films are
fabricated by very high frequency plasma enhanced chemical vapour deposition
(VHF-PECVD) at a silane concentration of 7% and a varying total gas flow
rate (Hk2+SiHk4). Relations between the total gas flow rate and the
electrical and structural properties as well as deposition rate of the films
are studied. The results indicate that with the total gas flow rate
increasing the photosensitivity and deposition
rate increase, but the crystalline
volume fraction (Xkc) and dark conductivity decrease.
And the intensity of (220) peak first increases then
decreases with the increase of the total gas flow rate. The cause for the
changes in the structure and deposition rate of the films with the total gas
flow rate is investigated using optical emission spectroscopy (OES). 相似文献
10.
High-Temperature Superconducting YBa2Cu3O7-δ Josephson Junction Fabricated with a Focused Helium Ion Beam
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As a newly developed method for fabricating Josephson junctions, a focused helium ion beam has the advantage of producing reliable and reproducible junctions. We fabricated Josephson junctions with a focused helium ion beam on our 50 nm YBa2Cu3O7-δ(YBCO) thin films. We focused on the junction with irradiation doses ranging from 100 to 300 ions/nm and demonstrated that the junction barrier can be modulated by the ion dose and that within this dose range, the junct... 相似文献
11.
Preparation of hydrogenated microcrystalline silicon films with hot-wire-assisted MWECR-CVD system
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Intrinsic hydrogenated microcrystalline silicon (\muc-Si:H) films have
been prepared by hot-wire-assisted microwave electron-cyclotron-resonance
chemical vapour deposition (HW-MWECR-CVD) under different deposition
conditions. Fourier-transform infrared spectra and Raman spectra were
measured. Optical band gap was determined by Tauc plots, and experiments of
photo-induced degradation were performed. It was observed that hydrogen
dilution plays a more essential role than substrate temperature in
microcrystalline transformation at low temperatures. Crystalline volume
fraction and mean grain size in the films increase with the dilution
ratio (R=H2/(H2+SiH4)).
With the rise of crystallinity in the films, the optical band gap tends to
become narrower while the hydrogen content and photo-induced degradation
decrease dramatically. The samples, were identified as \mu c-Si:H films, by
calculating the optical band gap. It is considered that hydrogen dilution
has an effect on reducing the crystallization activation energy of the
material, which promotes the heterogeneous solid-state phase transition
characterized by the Johnson--Mehl--Avrami (JMA) equation. The films with the
needed structure can be prepared by balancing deposition and crystallization
through controlling process parameters. 相似文献
12.
Preparation of few-layer graphene-capped boron nanowires and their field emission properties
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Large-area boron nanowire(BNW) films were fabricated on the Si(111) substrate by chemical vapor deposition(CVD). The average diameter of the BNWs is about 20 nm, with lengths of 5–10 μm. Then, graphene-capped boron nanowires(GC-BNWs) were obtained by microwave plasma chemical vapor deposition(MPCVD). Characterization by scanning electron microscopy indicates that few-layer graphene covers the surface of the boron nanowires. Field emission measurements of the BNWs and GC-BNW films show that the GC-BNW films have a lower turn-on electric field than the BNW films. 相似文献
13.
Electrically Tunable Wafer-Sized Three-Dimensional Topological Insulator Thin Films Grown by Magnetron Sputtering
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Three-dimensional(3 D) topological insulators(TIs) are candidate materials for various electronic and spintronic devices due to their strong spin-orbit coupling and unique surface electronic structure.Rapid,low-cost preparation of large-area TI thin films compatible with conventional semiconductor technology is the key to the practical applications of TIs.Here we show that wafer-sized Bi2 Te3 family TI and magnetic TI films with decent quality and well-controlled compositio... 相似文献
14.
OES study of the gas phase during diamond films deposition in high power DC arc plasma jet CVD system
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This paper used optical emission spectroscopy (OES) to study the gas
phase in high
power DC arc plasma jet chemical vapour deposition (CVD) during diamond films growth processes. The
results show that all the deposition parameters (methane concentration,
substrate temperature, gas flow rate and ratio of H2/Ar) could strongly
influence the gas phase. C2 is found to be the most sensitive radical
to deposition parameters among the radicals in gas phase. Spatially resolved
OES implies that a relative high concentration of atomic H exists near the
substrate surface, which is beneficial for diamond film growth. The
relatively high concentrations of C2 and CH are correlated with high
deposition rate of diamond. In our high deposition rate system, C2 is
presumed to be the main growth radical, and CH is also believed to
contribute the diamond deposition. 相似文献
15.
Titanium oxides (TiO2) and TiO2 films have recently attracted more attention on the application of microelectronic devices and microwave communication systems for processing temperature and environmentally stable dielectric properties characterized by high relative dielectric constant and low dielectric loss. Many deposition methods have been used to prepare TiO2 films including pulsed laser deposition, filered arc deposition, sol-gel method and reactive sputtering methods. Previous reports on TiO2 films prepared by MDO have primarily focused on surface mechanical and biologic properties, in contrast. 相似文献
16.
Characterization of doped hydrogenated nanocrystalline silicon films prepared by plasma enhanced chemical vapour deposition
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The B- and P-doped hydrogenated nanocrystalline silicon films
(nc-Si\jz{0.2ex}{:}H) are prepared by plasma-enhanced chemical
vapour deposition (PECVD). The microstructures of doped
nc-Si\jz{0.2ex}{:}H films are carefully and systematically
characterized by using high resolution electron microscopy
(HREM), Raman scattering, x-ray diffraction (XRD), Auger
electron spectroscopy (AES), and resonant nucleus reaction
(RNR). The results show that as the doping concentration of
PH3 increases, the average grain size (d) tends to
decrease and the crystalline volume percentage (Xc)
increases simultaneously. For the B-doped samples, as the doping
concentration of B2H\xj{6} increases, no obvious change in
the value of d is observed, but the value of Xc is
found to decrease. This is especially apparent in the case of
heavy B2H2 doped samples, where the films change from
nanocrystalline to amorphous. 相似文献
17.
Monolithic epitaxy and optoelectronic properties of single-crystalline γ-In2Se3 thin films on mica
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The growth of γ-In2Se3 thin films on mica by molecular beam epitaxy is studied. Single-crystalline γ-In2Se3 is achieved at a relatively low growth temperature. An ultrathin β-In2Se3 buffer layer is observed to nucleate and grow through a process of self-organization at initial deposition, which facilitates subsequent monolithic epitaxy of single-crystallineγ-In2Se3 at low temperature. Strong room-temperature photoluminescence and moderate optoelectronic response are observed in the achieved γ-In2Se3 thin films. 相似文献
18.
For ZnO/diamond structured surface acoustic wave (SAW) filters, performance is sensitively dependent on the quality of the ZnO films. In this paper, we prepare highly-oriented and fine grained polycrystalline ZnO thin films with excellent surface smoothness on the smooth nucleation surfaces of freestanding CVD diamond films by metal organic chemical vapour deposition (MOCVD). The properties of the ZnO films are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectrum. The influences of the deposition conditions on the quality of ZnO films are discussed briefly. ZnO/freestanding thick-diamond-film layered SAW devices with high response frequencies are expected to be developed. 相似文献
19.
LI Yanrong YANG Chun XUE Weidong LI Jinshan & LIU Yonghua .Institute of Microelectronics Solid State Electronics University of Electronic Science Technol- ogy of China Chengdu China .Institute of Mathematics Software Science Sichuan Normal University Chengdu China .Institute of Chemical Materials China Academy of Engineering Physics Mianyang China 《中国科学G辑(英文版)》2004,47(6)
Sapphire (α-Al2O3) and silicon (Si) are widely applied as the substrates of the highquality ZnO thin films prepared by pulse laser deposition (PLD) and molecule beamepitaxy (MBE) technology. The adhesion, diffusivity, and bonding of the particles on thesubstrates play a significant role in the forming and initial growing of nucleation for filmgrowth, and directly influence the quality of the entire thin films[1]. No sufficient studiesand experiments are available on the surface atomic str… 相似文献
20.
The boron nitride (BN) films containing cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN) were prepared by radio frequency a ssisted thermal filament chemical vapor deposition. The stress and strain in BN films were investigated by X-ray diffraction analysis using the sin2 ψ method. The results showed that both c-BN and h-BN in the same film have similar values of elastic strain, however, the compressive stress in c-BN is much greater than that in h-BN for the same film. Both stress and strain gradually decre ased with the increase of substrate temperature (Ts). The effective stress in the films calculated by the effective stress model increased with the increase of Ts. Furthermore, the dependence of effective stress in the films on Ts was also investigated. 相似文献