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1.
《Applied Superconductivity》1996,4(10-11):547-561
In recent years significant progress has been made in Jc enhancement in high Tc superconductors using melt texturing techniques. Among the many melt texturing methods and modifications, seeding and directional solidification techniques offer extensive control over the location of the growth front and the growth direction over long distances during melt texturing which makes these techniques most attractive from the standpoint of long conductor fabrication. These processes have the capability of producing Jcs of about 45 000 A cm−2 across single domains of YBCO. A novel variant of the conventional melt texturing process called the liquid phase removal method provides a means to improve the grain boundary coupling in melt textured bulk polycrystalline HTS. Grain boundaries in samples processed by this technique with misorientation angles as high as 54° have demonstrated Jcs as high as 18 000 A cm−2. Recent developments in texturing of RE-123 compounds (Nd and Yb) at high growth rates give promise for considerable reduction in processing times in directional solidification. Texturing has been observed even in samples processed at rates as high as 100 mm h−1. With these advances in melt texturing methods, utilization of bulk HTS in practical applications such as high capacity current leads etc., appears to be a distinct possibility of the near future. 相似文献
2.
《Applied Superconductivity》1996,4(10-11):487-493
Biaxially aligned yttria-stabilized zirconia (YSZ) films on Ni-based alloy substrates were realized with high deposition rate of 0.5 μm min−1 by the inclined substrate deposition (ISD) technique without ion beam assistance. The microstructure of YSZ was examined to study the growth mechanism of biaxial alignment by ISD. Columnar structures toward the plasma plume suggested a self-shadowing effect in the ISD process. To raise Ic values, YBCO thickness was increased up to 5 μm. Thick YBCO films with high Jc values were realized on the ISD-grown YSZ. Long YBCO tapes with biaxial alignment were successfully fabricated using continuous pulsed laser deposition and a high Ic value of 37.0 A (77.3 K, 0 T) at a 75 cm voltage tap spacing was achieved. 相似文献
3.
《Applied Superconductivity》1997,5(7-12):313-317
A technique for quantitative determination of the ultrathin films volume magnetization in the in-plane magnetizing field up to 104 A/m has been developed. This technique uses a scanning SQUID microscope with the YBCO thin film bicrystal dc SQUID and allows us also to reveal the orientation of the sample magnetization. A spatial resolution of about 100 μm and a field of view of 8×8 mm2 have been obtained. The resolution in terms of the magnetic moment of the studied film was close to 10−15 Am2/Hz1/2 at 1 Hz. 相似文献
4.
《Applied Superconductivity》1996,4(10-11):429-434
A coating system for the deposition of in-plane oriented yttria-stabilized zirconia (YSZ) template films on 1 cm wide flexible metal substrates is presented. In static mode, the system is capable of producing high quality template films on 20 cm substrate lengths. In a continuous coating mode, the system is capable of producing good quality template films on 1.1 m substrate lengths. Superconducting YBa2Cu3O7−δ (YBCO) films subsequently deposited onto these template films have demonstrated critical currents (Ic) of 200 A (1.5 cm length), 70 A (12 cm length) and 4 A (1 m length). 相似文献
5.
《Applied Superconductivity》1996,4(12):619-623
The off-diagonal Seebeck effect was investigated on a melt-textured YBa2Cu3O7−δ (YBCO) high-Tc superconductor. It was found that the transverse voltage Vx was proportional to the longitudinal temperature difference Δ Tz, measured directly with a pair of differential thermocouples, for textured samples with their c-axes tilted with respect to the surface’s normal. This supported the idea that the off-diagonal thermoelectric effect accounts for the anomalously high laser-induced transverse voltage on the oriented YBCO superconducting thin films. The variation of the Vx against the sample’s thickness d, at a given Δ Tz, deviated from the inversely proportional relationship when the sample was too thin. The deviation was discussed qualitatively in terms of deteriorated surface layers. The data of Vx(d) was fitted to obtain a reasonably reliable ∣ Sc−Sab∣ value of 12 μ V K−1. 相似文献
6.
The aim of this work was to develop high quality of CuIn1−xGaxSe2 thin absorbing films with x (Ga/In+Ga)<0.3 by sputtering without selenization process. CuIn0.8Ga0.2Se2 (CIGS) thin absorbing films were deposited on soda lime glass substrate by RF magnetron sputtering using single quaternary chalcogenide (CIGS) target. The effect of substrate temperature, sputtering power & working pressure on structural, morphological, optical and electrical properties of deposited films were studied. CIGS thin films were characterised by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Energy dispersive X-ray spectroscopy (EDAX), Atomic force microscopy (AFM), UV–vis–NIR spectroscopy and four probe methods. It was observed that microstructure, surface morphology, elemental composition, transmittance as well as conductivity of thin films were strongly dependent on deposition parameters. The optimum parameters for CIGS thin films were obtained at a power 100 W, pressure 5 mT and substrate temperature 500 °C. XRD revealed that thin film deposited at above said parameters was polycrystalline in nature with larger crystallite size (32 nm) and low dislocation density (0.97×1015 lines m−2). The deposited film also showed preferred orientation along (112) plane. The morphology of the film depicted by FE-SEM was compact and uniform without any micro cracks and pits. The deposited film exhibited good stoichiometry (Ga/In+Ga=0.19 and In/In+Ga=0.8) with desired Cu/In+Ga ratio (0.92), which is essential for high efficiency solar cells. Transmittance of deposited film was found to be very low (1.09%). The absorption coefficient of film was ~105 cm−1 for high energy photon. The band gap of CIGS thin film evaluated from transmission data was found to be 1.13 eV which is optimum for solar cell application. The electrical conductivity (7.87 Ω−1 cm−1) of deposited CIGS thin film at optimum parameters was also high enough for practical purpose. 相似文献
7.
《Materials Science in Semiconductor Processing》2012,15(5):555-558
Transparent conducting Al-doped ZnO (ZnO:Al, AZO) thin films were prepared at substrate temperature of 270 °C by pulsed direct current magnetron sputtering. NaOH solution (5 wt%) was employed to etch the AZO films at room temperature, and the surface textured AZO films were obtained successfully. The relationship between the surface textured structures and the etching process controlled by etching time was discussed. The textured morphology of the etched AZO films became clear as increasing the etching time, and the AZO film etched for 30 min exhibited uniformly and distinctly crater-like surface textured structure. Correspondingly, the haze and the resistivity increased with the increasing etching time. And the resistivity of the AZO film etched for 30 min was 3.2×10−3 Ω cm. 相似文献
8.
In the paper, SnOx thin films were deposited by reactive magnetron sputtering from a tin target in O2 containing working gas. The evolution from Sn-containing SnO to tetravalent SnO2 films was investigated. The films could be classified into three groups according to their optical band gaps, which are Eg<2.5 eV, Eg=3.0–3.3 eV and Eg>3.7 eV. The electric measurements show that high conductivity can be obtained much easier in SnO2 than in SnO films. A high electron mobility of 15.7 cm2 V−1 s−1, a carrier concentration of 1.43×1020 cm−3 and a resistivity of 2.8×10−3 Ω cm have been achieved in amorphous SnO2 films. Films with the optical band gap of 3.0–3.3 eV remain amorphous though the substrate temperature is as high as 300 °C, which implies that °btaining high mobility in p-type SnO is more challenging in contrast to n-type SnO2 films. 相似文献
9.
In this article X-ray radiation sensitivity of ZnS thin film prepared by a chemical bath deposition technique has been reported. The films were prepared under 0.10, 0.15 and 0.20 molarity (M). Characterization reports show that the 0.20 M film has the best quality than the other low molarity films. I-V characteristics of the films were studied under dark condition and observed that the film prepared at 0.20 M has an electrical conductivity of 2.06×10−6 (Ω cm)−1 which is about 10 times greater than the other lower molarity films. Further, the I-V characteristic of this film has studied under UV and X-ray radiations. The current under X-ray radiation is found to be significantly higher than that under the UV radiation. At a fix bias voltage of 1.0 V, the conductivity under UV radiation is found to be 3.26×10−6 (Ω cm)−1 whereas that under the X-ray is 4.13×10−5 (Ω cm)−1. The sensitivity under X-ray radiation is significantly greater than that under the UV radiation. This analysis suggests that the ZnS thin film which is used as a UV radiation sensor can also be used as a potential X-ray radiation sensor. 相似文献
10.
《Organic Electronics》2014,15(8):1799-1804
Copper phthalocyanine (CuPc)-based thin film transistors were fabricated using CuPc films grown under different deposition pressure (Pdep) (ranging from 1.8 × 10−4 Pa to 1.0 × 10−1 Pa). The transistor performance highly depended on Pdep. A field-effect mobility of 2.1 × 10−2 cm2/(V s) was achieved under 1.0 × 10−1 Pa. Detailed investigations revealed that Pdep modulates the molecular packing and orientation of the organic films grown on a SiO2/Si substrate and influences the charge transport. Furthermore, from a device physics point of view, contact resistance of the fabricated transistors decreased when Pdep increased, which was beneficial in reducing energy consumption. 相似文献
11.
《Applied Superconductivity》1996,4(12):603-618
Magnetic measurements and structural investigation have been performed on melt-textured YBCO and AgYBCO HTS. The “sun” technique produces very dense YBCO (ρ=5.86 g cm−3) and AgYBCO [ρ=6.36 g cm−3; 10% b/w (by weight) silver. This technique renders samples with a large volume fraction of the Y2BaCuO5 (211) phase. The material is characterized by very high Jc values, as compared with bulk polycrystalline YBCO prepared by other methods. This feature is attributed to the enhanced amount of 211 particles which serve as pinning centers. Additional significant densification of the structure due to silver incorporation is obtained, and a reduction of the size of 211 inclusions is also observed. Silver doped samples show “butterfly”-like hysteresis loops at relatively high temperatures (T≥60K). This feature is probably associated with oxygen deficiency which arises from the slower oxygen diffusion into silver doped samples. Jc values enhancement was obtained in silver doped “sun” samples at high temperatures (T≥60K) and fields of 20–30 kOe. The temperature dependence of effective activation energy of pinning, Ueff, was measured for YBCO and AgYBCO materials. Ueff is higher in silver doped samples in the high temperature region T≥60K. 相似文献
12.
Fluorine-doped tin oxide (FTO) films were prepared by an improved sol-gel process, in which FTO films were deposited on glass substrates using evaporation method, with the precursors prepared by the conventional sol-gel method. The coating and sintering processes were combined in the evaporation method, with the advantage of reduced probability of films cracking and simplified preparation process. The effects of F-doping contents and structure of films on properties of films were analyzed. The results showed the performance index (ΦTC=3.535×10−3 Ω−1 cm) of the film was maximum with surface resistance (Rsh) of 14.7 Ω cm−1, average transmittance (T) of 74.4% when F/Sn=14 mol%, the reaction temperature of the sol was 50 °C, and the evaporation temperature was 600 °C in muffle furnace, and the film has densification pyramid morphology and SnO2−xFx polycrystalline structure with tetragonal rutile phase. Compared with the commercial FTO films (ΦTC=3.9×10−3 Ω−1 cm, Rsh=27.4 Ω cm−1, T=80%) produced by chemical vapor deposition (CVD) method, the ΦTC value of FTO films prepared by an improved sol-gel process is close to them, the electrical properties are higher, and the optical properties are lower. 相似文献
13.
The authors report a method of enhancing the conductivity of TiO2 films by controlling their structural phases. Thin films of Nb:TiO2 (TNO) were prepared on glass and silicon substrates by RF sputtering with varying Nb content at 200 °C. It is shown that fine control over the structural phases of TiO2 is critical for achieving low resistivity. The resistivity values of the films doped with oxygen vacancies and Nb+5 decreased from 3.8 × 10−1 to 4.1 × 10−3 Ω cm when the weight percent of rutile in anatase-rutile phase mixture decreases from 52.8% to 32%. Furthermore, the lowest resistivity value of 2.37 × 10−3 Ω cm was obtained for the doped TiO2 films having single phase anatase structure. The physical processes responsible for the diverse electrical properties are discussed and are associated with the growth conditions. Our result indicates that highly conductive doped-TiO2 film can be obtained by controlling the anatase phase formation via the growth temperature. The obtained results can significantly contribute to the development of transparent electrodes by RF sputtering, a suitable technique for coating large area substrates. 相似文献
14.
We report on transparent and flexible amorphous In–Zn–Al–O (a-IZAO) films prepared by roll-to-roll (RTR) sputtering for use as anodes in acidic buffer free flexible organic solar cells (FOSCs). The presence of Zn and Al structural stabilizers in the In2O3 matrix produced a completely amorphous structure with the high optical transmittance of 89.25% and the low resistivity of 2.123 × 10−3 Ω-cm, as well as the high work function of 5.14 eV, making the a-IZAO films suitable for use as flexible anodes for FOSCs. In addition, the a-IZAO films showed no change in resistance (ΔR) during outer and inner bending fatigue tests due to their good mechanical flexibility. Relative to the power conversion efficiency (1.944%) of a PEDOT:PSS-based FOSCs, a FOSC fabricated by using an a-IZAO anode and without the use of acidic PEDOT:PSS buffer showed greater power conversion efficiency (2.509%), owing to the absence of interfacial reactions between the acidic PEDOT:PSS and the a-IZAO anode. 相似文献
15.
In the present communication, the binary CdSe and quaternary Cd1-xZnxSe1-ySy (0 ≤ x = y ≤ 0.35) thin films were synthesized using a chemical bath deposition. Thin film deposition was carried out at the optimized conditions (pH = 10 ± 0.1, deposition temperature = 70 ± 0.1 °C, deposition time = 100 min and substrate rotation speed = 65 ± 2 rpm). X-ray diffraction studies confirmed hexagonal-wurtzite crystal structure with the formation of quaternary Cd(Zn, S)Se phase along with binary CdSe, CdS, ZnS and ZnSe, phases of the as-grown Cd1-xZnxSe1-ySy thin films. Elemental analysis showed presence of Cd2+, Zn2+, S2- and Se2- in the deposited films. Fourier transform infrared spectroscopy shown the bands at 911.15 cm−1 – 901.62 cm−1 which are assigned to the stretching frequency of Cd–Se bond. Scanning electron microscopy show transformation of the microstructure from globular crystallites to a rhomboid flake like network. The electrical conductivity was typically ≈ 10−7 Ω−1 cm−1. At low temperatures, the conduction was by variable range hopping, and this changed to thermally activated grain boundary dominated conduction for T > 350 K. 相似文献
16.
FeS2 thin films were grown on a glass substrate using a physical vapor deposition technique at room temperature. Subsequently, the thin films were annealed in two different atmospheres: vacuum and vacuum-sulfur. In the vacuum-sulfur atmosphere a graphite box was used as sulfur container and the films were sulfurated successfully at 200–350 ºC. It was found that annealing in a vacuum-sulfur atmosphere was indispensable in order to obtain polycrystalline FeS2 thin films. The polycrystalline nature and pure phase were determined by XRD and Raman techniques and the electrical properties by the Hall effect. Using the sulfurating technique, the n-type semiconductor was prepared at 200–350 °C and a p-type at 500 °C. The carrier concentrations were between 1.19×1020 and 2.1×1020 cm−3. The mobility was 9.96–5.25 cm2 V−1 s−1 and the resistivity was 6.31×10−2 to 1.089×10−2 Ω cm. The results obtained from EDS showed that the films prepared in the vacuum-sulfur atmosphere were close to stoichiometric and that the indirect band gap varied between 1.03 and 0.945 eV. 相似文献
17.
A facile chemical reduction approach for effectively tuning thermoelectric properties of PEDOT films
Poly(3,4-ethylenedioxythiophene)–tosylate–polyethylene glycol–polypropylene glycol–polyethylene glycol (PEDOT–Tos–PPP) films were prepared via a vapor phase polymerization (VPP) method. The films possess good electrical conductivity (1550 S cm−1), low Seebeck coefficient (14.9 μV K−1) and thermal conductivity (0.501 W m−1 K−1), and ZT ∼ 0.02 at room temperature (RT, 295 K). Then, the films were treated with NaBH4/DMSO solutions of different NaBH4 concentrations to adjust the redox level. After the NaBH4/DMSO treatment (dedoping), the electrical conductivity of the films continuously decreased from 1550 to 5.7 S cm−1, whereas the Seebeck coefficient steeply increased from 14.9 to 143.5 μV K−1. A maximum power factor of 98.1 μW m−1 K−2 has been achieved at an optimum redox level. In addition, the thermal conductivity of the PEDOT–Tos–PPP films decrease from 0.501 to 0.451 W m−1 K−1 after treated with 0.04% NaBH4/DMSO solution. A maximum ZT value of 0.064 has been achieved at RT. The electrical conductivity and thermal conductivity (Seebeck coefficient) of the untreated and 0.04% NaBH4/DMSO treated PEDOT–Tos–PPP films decrease (increases) with increasing temperature from 295 to 385 K. And the power factor of the films monotonically increases with temperature. The ZT at 385 K of the 0.04% NaBH4/DMSO treated film is 0.155. 相似文献
18.
《Materials Science in Semiconductor Processing》2007,10(4-5):167-172
Gallium (Ga)-doped zinc oxide (ZnO:Ga) transparent conductive films were deposited on glass substrates by DC reactive magnetron sputtering. Effects of deposition pressure on the structural, electrical and optical properties of ZnO:Ga films were investigated. X-ray diffraction (XRD) studies show that the films are highly oriented with their crystallographic c-axis perpendicular to the substrate almost independent of the deposition pressure. The morphology of the film is sensitive to the deposition pressure. The transmittance of the ZnO:Ga thin films is over 90% in the visible range and the lowest resistivity of ZnO:Ga films is 4.48×10−4 Ω cm. 相似文献
19.
High-κ TiO2 thin films have been fabricated using cost effective sol–gel and spin-coating technique on p-Si (100) wafer. Plasma activation process was used for better adhesion between TiO2 films and Si. The influence of annealing temperature on the structure-electrical properties of titania films were investigated in detail. Both XRD and Raman studies indicate that the anatase phase crystallizes at 400 °C, retaining its structural integrity up to 1000 °C. The thickness of the deposited films did not vary significantly with the annealing temperature, although the refractive index and the RMS roughness enhanced considerably, accompanied by a decrease in porosity. For electrical measurements, the films were integrated in metal-oxide-semiconductor (MOS) structure. The electrical measurements evoke a temperature dependent dielectric constant with low leakage current density. The Capacitance–voltage (C–V) characteristics of the films annealed at 400 °C exhibited a high value of dielectric constant (~34). Further, frequency dependent C–V measurements showed a huge dispersion in accumulation capacitance due to the presence of TiO2/Si interface states and dielectric polarization, was found to follow power law dependence on frequency (with exponent ‘s’=0.85). A low leakage current density of 3.6×10−7 A/cm2 at 1 V was observed for the films annealed at 600 °C. The results of structure-electrical properties suggest that the deposition of titania by wet chemical method is more attractive and cost-effective for production of high-κ materials compared to other advanced deposition techniques such as sputtering, MBE, MOCVD and ALD. The results also suggest that the high value of dielectric constant ‘κ‘ obtained at low processing temperature expands its scope as a potential dielectric layer in MOS device technology. 相似文献
20.
CuCr0.93Mg0.07O2 thin films were successfully deposited by DC reactive magnetron sputtering at 1123 K from metallic targets. The influence of film thickness on the structural and optoelectronic properties of the films was investigated. X-ray diffraction (XRD) results revealed that all the films had a delafossite structure with no other phases. The optical and electrical properties were investigated by UV–VIS spectrophotometer and Hall measurement, respectively. It was found that the optoelectronic properties exhibited a thickness-dependent behavior. The optical band gap and the average transmittance of the films showed a monotonous decrease with respect to the increase in thickness. The average transmittance in the visible region decreased from 67% to 47% as the thickness increased from ~70 nm to ~280 nm. Simultaneously, the conductivity of the films fell from 1.40 S∙cm−1 to 0.27 S∙cm−1. According to Haacke's figure of merit (FOM), a film with a maximum FOM value of about 1.72×10−7 Ω−1 can be achieved when the thickness is about 70 nm (σ≈ 1.40 S·cm−1 and Tav. ≈67%). 相似文献