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1.
YBa_2Cu_3O_(7-δ)(YBCO) films were deposited on(100)-oriented LaAlO_3(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 superconducting 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 t... 相似文献
2.
Cukauskas E.J. Pond J.M. Dobisz E.A. DeSisto W.J. 《Applied Superconductivity, IEEE Transactions on》2000,10(3):1649-1656
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 (Tc). The temperature dependence of the critical current near Tc was quadratic-like and strongly dependent on the value of Tc used in the analysis. For the two orientations, there was nearly a 6 K difference in Tc 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 相似文献
3.
Chen J. Yamashita T. Sasahara H. Suzuki H. Kurosawa H. Hirotsu Y. 《Applied Superconductivity, IEEE Transactions on》1991,1(2):102-107
The DC and AC Josephson effects were observed in YBa2Cu 3O7-a (YBCO) bridges with metal-organic chemical vapor deposited (MOCVD) thin films on (100)MgO substrates. In TEM observations and X-ray analysis, the angle grain boundaries (AGBs) in these films were observed. Josephson junction resulting from the AGBs showed the semiconducting barrier junction property dominantly, and the AGBs consisted of YBCO with oxygen deficiency. Based on these results, the authors propose a three-terminal device with the Josephson junction. The Josephson junction can be prepared by depositing an epitaxial YBCO thin film with one AGB on a bicrystal (100)SrTiO3 or (100)Si substrate, and the insulated gate for the application of electric field to the AGB is formed over the junction. The supercurrent in the Josephson junction is controlled by the electric field effect of the semiconducting AGB in the junction 相似文献
4.
Misra M. Kataria N.D. Pinto R. Tonouchi M. Srivastava P. 《Applied Superconductivity, IEEE Transactions on》2001,11(4):4128-4135
The microwave surface resistance, Rs measurement of YBa 2Cu307 -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 Rs -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 相似文献
5.
Fisher M.A. Cukauskas E.J. Allen L.H. 《Applied Superconductivity, IEEE Transactions on》1997,7(1):1-6
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 相似文献
6.
Orsal G. Romain N. Artaud M.-C. Duchemin S. 《Electron Devices, IEEE Transactions on》1999,46(10):2098-2102
CuGaSe2 thin films have been grown by metalorganic chemical vapor deposition (MOCVD), from three organometallic precursors. Samples of about 1-2 μm thick are codeposited onto Pyrex and Mo-coated soda lime glass. A large range of compositions was investigated and characterized. Stoichiometric CuGaSe2 thin films are single-phased and their optical bandgap is about 1.68 eV. The features of the films are presented in relation with their composition. XRD spectra always exhibit a preferential orientation along the (112) plane. Secondary phases have been observed: Cu2Se for Cu-rich films, CuGa3Se5 for Ca-rich films. Observation of the morphology reveals larger polyhedral grains for Cu-rich films becoming platelet-shaped and tilted for Ga-rich compounds. The optical properties are also sensitive to the compositional changes and related to the eventual presence of binary phases. The gap increases with the Ga-content. The CuGa3Se5, phase exhibit a gap of about 1.85 eV. All the samples have a p-type conductivity 相似文献
7.
Huey-Daw Wu Zhihang Zhang Barnes F. Jackson C.M. Kain A. Cuchiaro J.D. 《Applied Superconductivity, IEEE Transactions on》1994,4(3):156-160
In this paper we report the construction of both slot capacitors on bulk substrate and thin film interdigital capacitors using YBa2 Cu3O7-δ (YBCO) and BaxSr 1-xTiO3. Slot capacitors made on bulk Bax Sr1-xTiO3 (BST) yielded variations in capacitance of more than 6 to 1 at 86 K with a peak electric field strength of 25 kV/cm. With a metal organic deposition (MOD) grown BaxSr1-xTiO3 300-nm overcoat on a YBCO thin film, an interdigital capacitor on LaAlO3 substrate yielded an approximate tuning range of 10% for peak field of 66 kV/cm over temperatures ranging from 50 K to 120 K 相似文献
8.
L. Le Brizoual S. Guilet G. Lemprire A. Granier N. Coulon M. Lancin G. Turban 《Microelectronic Engineering》2000,50(1-4):509-513
Thin films of Ti–Si–N are deposited by r.f. magnetron sputtering in a Ar/N2 gas mixture. The magnetron discharge is operated at 10 mTorr with 5 and 10% N2 in the gas mixture and r.f. powers ranging from 100 to 200 W. The composition and electrical resistivity of the thin films were determined by energy dispersive X-ray spectroscopy and the four-point probe method, respectively. The structure of the films was determined by high-resolution transmission electron microscopy. The Ti–Si–N films were either amorphous or contained cubic TiN nanosized grains in an amorphous phase. The diffusion barrier properties of 10-nm thick film between Cu and Si were studied from 500 to 700°C. The highest failure temperature of 650°C was obtained for Ti37.5 Si27 N35.5 which. contains 4-nm TiN crystallites in an amorphous phase. 相似文献
9.
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. 相似文献
10.
Mo, Pt, Pt/Mo and Pt/Ti thin films have been deposited onto Si and SiO2 substrates by RF sputtering and annealed in the YBa2Cu3O7−δ (YBCO) growth conditions. The effect of annealing on the sheet resistance of unpatterned layers was measured. A Pt-based multilayered metallization for the PMOS devices was proposed and tested for a compatible monolithic integration of semiconducting devices and YBCO sensors on the same silicon substrate. The best results were obtained with a Pt/Ti/Mo-silicide structure showing 0.472 Ω□ interconnect sheet resistivity and 2×10−4 Ω cm2 specific contact resistivity after annealing for 60 min at 700 °C in 0.5 mbar O2 pressure. 相似文献
11.
Maeno M. Nakagawa Y. Miki N. Ohmi T. 《Semiconductor Manufacturing, IEEE Transactions on》1992,5(2):107-113
The optimum conditions for the fluorine passivation of 316L stainless steel are described. The direct fluoridation products formed at temperatures of 320°C or lower are composed solely of FeF2 , while those which were formed at the temperatures of 330°C or higher have a compound-phase composition of FeF2 and FeF 3. At a critical temperature (400°C for 316L stainless steel) of the thermal modification process, FeF3 is converted to FeF2 and disappears completely as the temperature rises. Meanwhile, CrF3 is formed at a certain temperature (440°C for 316L stainless steel). The two-phase composition gets further crystallized as the thermal modification temperature rises. As the crystal growth induces the cracks on the fluoridated film, it is very difficult to form a satisfactory passivation film from the two-phase composition by thermal modification. It is confirmed that excellent passivation film has been obtained from the single-phase composition by the optimum fluoridation following the optimum thermal modification 相似文献
12.
King T.-J. McVittie J.P. Saraswat K.C. Pfiester J.R. 《Electron Devices, IEEE Transactions on》1994,41(2):228-232
The electrical properties of polycrystalline silicon-germanium (poly-Si1-xGex) films with germanium mole fractions up to 0.56 doped by high-dose ion implantation are presented. The resistivity of heavily doped p-type (P+) poly-Si1-x Gex is much lower than that of comparably doped poly-Si, because higher levels of boron activation and higher hole mobilities are achieved in poly-Si1-xGex. The resistivity of heavily doped n-type (N+) poly-S1-xGex is similar to that of comparably doped poly-Si for x<0.45; however, it is considerably higher for larger Ge mole fractions due to significant reductions in phosphorus activation. Lower temperatures (~500°C), as well as lower implant doses, are sufficient to achieve low resistivities in boron-implanted poly-Si1-xGex films, compared to poly-Si films. The work function of P+ poly-Si1-xGex decreases significantly (by up to ~0.4 Volts), whereas the work function of N+ poly-Si1-xGex decreases only slightly, as Ge content is increased. Estimates of the energy bandgap of poly-Si1-xGex show a reduction (relative to the bandgap of poly-Si) similar to that observed for unstrained single-crystalline Si1-xGex for a 26% Ge film, and a reduction closer to that observed for strained single-crystalline Si 1-xGex for a 56% Ge film. The electrical properties of poly-Si1-xGex make it a potentially favorable alternative to poly-Si for P+ gate-material applications in metal-oxide-semiconductor technologies and also for p-channel thin-film transistor applications 相似文献
13.
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 Zs=Rs+jXs 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 Rs 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. Zs for the best optimised films appears to be insensitive to the effects of patterning 相似文献
14.
Fork D.K. Fenner D.B. Barrera A. Phillips J.M. Geballe T.H. Connell G.A.N. Boyce J.B. 《Applied Superconductivity, IEEE Transactions on》1991,1(1):67-73
Efforts aimed at producing device-quality YBa2Cu3 O7-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, T c (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 相似文献
15.
A selected-area CVD method for deposition of sensing films onmonolithically integrated gas detectors
A novel method for deposition of thin transducing films on geometrically well-defined areas is reported. The films represent the front-end of monolithically integrated microelectronic gas detectors. These devices contain a 1 μm thick dielectric window equipped with four-point probe electrodes and a boron-diffused silicon heater underneath the window. The central region of the window can be instantaneously switched from room temperature to several hundred °C while maintaining excellent thermal uniformity within a 350×350 μm area. Thermally activated CVD of Pt is realized on the heated region by raising the temperature of the central region into the regime of thermal decomposition of Pt precursors such as Pt(PF3)4. The growth of thin Pt films is monitored in situ by measuring film resistance, and film growth is terminated once desired film resistance values are reached by cutting off the heater current. This allows to optimize film properties for gas sensing applications. The deposited films are characterized ex situ by optical microscopy and scanning electron microscopy to correlate film morphology with resistance. This method can be easily extended to deposition of other films of interest such as TiO2 相似文献
16.
High dose-rate plasma ion implantation (PII) has been utilized to produce low dielectric constant (k) SiO2 films for high quality interlayer dielectrics. The SiO2 films are fluorine-doped/carbon-doped by PII with CF4 plasma in an inductively-coupled plasma (ICP) reactor. It is found that the use of CF 4 doping results in exceptional dielectric properties which differ significantly from fluorinated SiO2. The dielectric constant of the SiO2 film is reduced from 4.1 to 3.5 after 5 minute PII, other electrical parameters such as bulk resistivity and dielectric breakdown strength are also improved 相似文献
17.
Hyo-Sang Choi Ok-Bae Hyun Hye-Rim Kim Kwon-Bae Park 《Applied Superconductivity, IEEE Transactions on》2002,12(3):1833-1838
Presents investigations of a hybrid type superconducting fault current limiter (SFCL), which consists of transformers and resistive superconducting switches. The secondary windings of the transformer were separated into several electrically isolated circuits and linked inductively with each other by mutual flux, each of which has a superconducting current limiting unit of YBa2Cu3O 7 (YBCO) stripes as a switch. Simple connection in series of the SFCL switches tends to produce ill-timed switching because of power dissipation imbalance between SFCL units. Both electrical isolation and mutual flux linkage of the switches provides a solution to power dissipation imbalance, inducing simultaneous switching by independent quenches and current redistribution of the YBCO films. This design enables increase of voltage ratings of SFCL with given YBCO stripes 相似文献
18.
Chorey C.M. Miranda F.A. Bhasin K.B. 《Applied Superconductivity, IEEE Transactions on》1991,1(4):178-180
Microwave transmission measurements through YBa2Cu3O7-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 相似文献
19.
A curved spiral antenna above a finite hollow conducting cylinder is analyzed using the method of moments. The effects of cylinder length 2H and cylinder radius rcy on the radiation characteristics of the spiral are evaluated. As 2H increases, the cross-polarization component of the radiation field in the broadside direction decreases to a constant value (approximately -18 dB). When 2H is greater than one wavelength (λ0), the input impedance of the spiral above a cylinder of radius rcy=0.25 λ0 is almost constant (250-j20 Ω) with a gain of approximately 7 dB. The spiral above a cylinder of (2H, rcy)=(2.7 λ0, 0.25 λ0) shows a 3-dB axial ratio bandwidth of approximately 23%, which is wider than a flat spiral antenna above a flat ground plane of infinite extent 相似文献
20.
Takashi Fukui 《Microelectronics Journal》1993,24(8):795-803
(AlAs)1/2(GaAs)1/2 fractional-layer superlattices (FLSs) are grown on a (001) vicinal substrate by metalorganic chemical vapor deposition (MOCVD). FLSs are new types of lateral superlattice with a period of 4–20 nm. The uniform superlattice period is observed over a large surface area by bright field transmission electron microscopy (TEM). The results suggest the ideal growth from a kink site occurs during MOCVD growth, and the distances between kink sites are equal.
Polarization-dependent photoluminescence and optical absorption spectra of FLSs are also observed. Electron wave interference devices with a lateral periodic potential have been fabricated. 相似文献