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1.
Highly transparent and conductive scandium doped zinc oxide (ZnO:Sc) films were deposited on c-plane sapphire substrates by sol–gel technique using zinc acetate dihydrate [Zn(CH3COO)2·2H2O] as precursor, 2-methoxyethanol as solvent and monoethanolamine as a stabilizer. The doping with scandium is achieved by adding 0.5 wt% of scandium nitrate hexahydrate [(ScNO3·6H2O)] in the solution. The influence of annealing temperature (300–550 °C) on the structural, optical and electrical properties was investigated. X-ray Diffraction study revealed that highly c-axis oriented films with full-width half maximum of 0.16° are obtained at an annealing temperature of 400 °C. The surface morphology of the films was judged by SEM and AFM images which indicated formation of grains. The average transmittance was found to be above 92% in the visible region. ZnO:Sc film, annealed at 400 °C exhibited minimum resistivity of 1.91 × 10−4 Ω cm. Room-temperature photoluminescence measurements of the ZnO:Sc films annealed at 400 °C showed ultraviolet peak at 3.31eV with a FWHM of 11.2 meV, which are comparable to those found in high-quality ZnO films. Reflection high-energy electron diffraction pattern confirmed the epitaxial nature of the films even without introducing any buffer layer. 相似文献
2.
A single-step melt-quench in situ thermochemical reduction technique has been used to synthesize a new series of Au° nanoparticles embedded antimony glass–ceramic (K2O–B2O3–Sb2O3–ZnO) dichroic nanocomposites. X-ray and selected area electron diffractions manifest growth of Au° nanoparticles along (2 0 0) planes. The particle sizes obtained from X-ray diffraction patterns are found to vary in the range 4–21 nm. Dichroic behavior is attributed to the elliptical shape gold nanoparticles having aspect ratio 1.2, as observed from the transmission electron microscopy (TEM) images. The Au° nanoparticles exhibit surface plasmon resonance band (SPR) around 600 nm, which experiences red-shifts with increasing Au concentration. These nanocomposites when co-doped with Sm2O3 and excited at 949 nm, exhibit 2-fold intensification of 636 nm red emission transition (4G5/2 → 6H9/2) due to SPR induced local field enhancement of Au° nanoparticles and are promising materials for display applications. 相似文献
3.
Sputtered Cr/n-GaAs Schottky diodes have been prepared and annealed at 200 and 400 °C. The current–voltage (I–V) characteristics of the as-deposited and annealed diodes have been measured in the temperature range of 60–320 K with steps of 20 K. The effect of thermal annealing on the temperature-dependent I–V characteristics of the diodes has been investigated experimentally. The ideality factor and barrier height (BH) values for 400 °C annealed diode approximately remain unchanged from 120 to 320 K, and those of the as-deposited sample from 160 to 320 K. The departures from ideality at low temperatures have been ascribed to the lateral fluctuations of the BH. The BH values of 0.61 and 0.74 eV for the as-deposited and 400 °C annealed diodes were obtained at room temperature, respectively. A Richardson constant value of 9.83 A cm−2 K−2 for 400 °C annealed Schottky diode, which is in close agreement with the known value of 8.16 A cm−2 K−2 for n-type GaAs. Furthermore, T0 anomaly values of 15.52, 10.68 and 5.35 for the as-deposited and 200 and 400 °C annealed diodes were obtained from the nT versus T plots. Thus, it has been seen that the interface structure and quality improve by the thermal annealing at 400 °C. 相似文献
4.
T. Naito K. Sato D. Yamaguchi H. Fujishiro 《Physica C: Superconductivity and its Applications》2009,469(15-20):1218-1220
We have studied the effect of a small amount of Y-site substitution by La or Pr ions on the vortex pinning in the Y–Ba–Cu–O system. (Y1-xLax)–Ba–Cu–O and (Y1-xPrx)–Ba–Cu–O bulks were fabricated by the melt-textured growth, in which x was varied from 0 to 0.01. The critical current density Jc at 77 K is improved in magnetic fields parallel to the c-axis above 2–4.5 T and the corresponding irreversibility field, Hirr, shifts to the higher value in both bulks. 相似文献
5.
Ceramics with formula (1 − x)Pb(Zr0.52Ti0.48)O3–x(Bi3.25La0.75)Ti3O12 (when x = 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) were prepared by a solid-state mixed-oxide method and sintered at temperatures between 950 °C and 1250 °C. It was found that the optimum sintering temperature was 1150 °C at which all the samples had densities at least 95% of theoretical values. Phase analysis using X-ray diffraction indicated the existence of BLT- as well as PZT-based solid solutions with corresponding lattice distortion. Scanning electron micrographs of ceramic surfaces showed a plate-like structure in BLT-rich phase while the typical grain structure was observed for PZT-rich phase. The grain sizes of both pure BLT and PZT ceramics were found to decrease as the relative amount of the other phase increased. This study suggested that tailoring of properties of this PZT–BLT system was possible especially on the BLT-rich side due to its large solubility limit. 相似文献
6.
Two series of mixed copper ferrites, Cu1+x Gex Fe2−2x O4 and Cu1+x Six Fe2−2x O4, have been analogously investigated for x=0.0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3. The two systems were prepared using the standard ceramic techniques. X-ray diffraction analysis indicates that both systems formed in a single phase cubic spinel structure. The lattice parameter has a constant value (0.838 nm±0.001) for the two series. The grain diameter was estimated from the scanning electron microscope micrographs for the two series. Some magnetic properties were measured at room temperature. The magnetization M was measured in the range of magnetizing field up to 5500 Am−1. The relative permeability (μr) was calculated from the B–H relation. The B–H loops were measured at constant magnetizing current (I=2.5 A which is equivalent to 900 Am−1). Also, the hystersis area and the magnetic parameters Br, Bs, mR (Br/Bs) and apparent energy loss (E) were estimated from the B–H loops; μr, Br, Bs and E are composition dependent. 相似文献
7.
B. Shinozaki N. Kokubo K. Makise S. Takada T. Yamaguti S. Ogura K. Yamada K. Yano K. Terai S. Tomai H. Nakamura 《Physica C: Superconductivity and its Applications》2009,469(15-20):956-959
We have investigated the relation among ρ–T characteristics, superconductivity, annealing conditions and the crystallinity of polycrystalline (In2O3)1−x–(ZnO)x films. We annealed as-grown amorphous films in air by changing annealing temperature and time. It is found that the films annealed at 200 °C or 300 °C for a time over 0.5 h shows the superconductivity. Transition temperature Tc and the carrier density n are Tc < 3.3 K and n ≈ 1025–1026 m−3, respectively. Investigations for films with x = 0.01 annealed at 200 °C have revealed that the Tc, n and crystallinity depend systematically on annealing time. Further, we consider that there is a suitable annealing time for sharp resistive transition because the transition width becomes wider with longer annealing times. We studied the upper critical magnetic field Hc2(T) for the film with different annealing time. From the slope of dHc2/dT for all films, we have obtained the resistivity ρ dependence of the coherence length ξ(0) at T = 0 K. 相似文献
8.
D.W. Kwak H.Y. Cho W.-C. Yang 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):153
This study explores the nucleation and morphological evolution of silicon nanowires (Si-NWs) on Si (0 0 1) and (1 1 1) substrates synthesized using nanoscale Au–Si island-catalyzed rapid thermal chemical vapor deposition. The Au–Si islands are formed by Au thin film (1.2–3.0 nm) deposition at room temperature followed by annealing at 700 °C, which are employed as a liquid-droplet catalysis during the growth of the Si-NWs. The Si-NWs are grown by exposing the substrates with Au–Si islands to a mixture of gasses SiH4 and H2. The growth temperatures and the pressures are 500–600 °C and 0.1–1.0 Torr, respectively. We found a critical thickness of the Au film for Si-NWs nucleation at a given growth condition. Also, we observed that the dimensional evolution of the NWs significantly depends on the growth pressure and temperature. The resulting NWs are 30–100 nm in diameter and 0.4–12.0 μm in length. For Si (0 0 1) substrates 80% of the NWs are aligned along the 1 1 1 direction which are 30° and 60° with respect to the substrate surface while for Si (1 1 1) most of the NWs are aligned vertically along the 1 1 1 direction. In particular, we observed that there appears to be two types of NWs; one with a straight and another with a tapered shape. The morphological and dimensional evolution of the Si-NWs is significantly related to atomic diffusion kinetics and energetics in the vapor–liquid–solid processes. 相似文献
9.
Homogeneous glasses in the Na2O–B2O3–Al2O3–SiO2 system doped with proper amount of AgCl were obtained by melting at a temperature of 1450 °C. Then, with several steps of treatment, including crystallization, elongation and reduction, the glass with oriented arrangement of needle-like micro–nano silver particles was produced. The microstructure and the optical properties of the glass samples in different stages were studied by SEM-EDAX, FE-SEM and UV–Vis spectrum. The results showed that the glass after elongation and reduction exhibits excellent polarization performance in the wavelength range from 600 nm to 900 nm, with an extinction ratio larger than 45 dB. The glass only elongated shows also slight polarizing performance, which may result from the formation of filament structure of Ag during elongation processing. 相似文献
10.
Yoshio Tatamitani Akinori Sato Yoshiyuki Kawashima Nobukimi Ohashi James M. LoBue Eizi Hirota 《Journal of Molecular Spectroscopy》2009,257(1):11-19
The rotational spectra of three isotopomers of the Ar–dimethyl sulfide (DMS) complex – normal, 34S, and 13C species – were measured in the frequency region from 3.7 up to 24.1 GHz by Fourier transform microwave spectroscopy. The normal species yielded 43 a-type and 79 c-type transitions. No Ar tunneling splitting was observed, while many transitions were split by the internal rotation of the two methyl tops of the DMS unit. In cases where the K-type splitting was close to that due to methyl internal-rotation, several forbidden transitions were observed that followed b-type selection rules. All of the observed transition frequencies were analyzed simultaneously using a phenomenological Hamiltonian also used in previously published work describing the Ar–dimethyl ether (DME) and Ne–DME complexes. The rotational and centrifugal distortion constants and the potential barrier height to methyl-top internal rotation, V3, were determined. The rotational constants were consistent with an Ar–DMS center of mass (cm) distance of 3.796 (3) Å and a S–cm–Ar angle of 104.8 (2)°. The V3 potential barrier obtained, 736.17 (32) cm−1, was 97.8% of the DMS monomer barrier. By assuming a Lennard–Jones-type potential, the dissociation energy was estimated to be 2.4 kJ mol−1, which was close to the value for Ar–DME, 2.5 kJ mol−1. 相似文献
11.
K. G. Grigorov G. I. Grigorov M. Stoyanova J. L. Vignes J. P. Langeron P. Denjean J. Perriere 《Applied Physics A: Materials Science & Processing》1992,55(5):502-504
Two kinds of reactively evaporated titanium nitride films with columnar (B
0 films) and fine-grained film structure (B
+ films) have been examined as diffusion barriers, preventing the silicon diffusion in silicon devices. The silicon diffusion profiles have been investigated by 2 MeV 4He+ Rutherford backscattering spectrometry (RBS) after annealing at temperatures up to 900° C, in view of application of high-temperature processes. The diffusivity from 400 to 900° C: D (m2 s–1)=2.5×10–18 exp[–31 kJ/mol/(RT)] in B
0 layers and D (m2 s–1)=3×10–19 exp[–26 kJ/mol/(RT) in B
+ TiN layers. The diffusivities determined correspond to grain boundary diffusion, the difference being due to the different microstructure. The very low diffusivity of silicon in B
+ TiN layer makes it an excellent high-temperature barrier preventing silicon diffusion. 相似文献
12.
Shuichi Ishida Keiki Takeda Atsushi Okamoto Ichiro Shibasaki 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):211
Distinctive magnetoresistance (MR) effects in weak magnetic fields before the appearance of Shubnikov–de Haas (SdH) oscillations at low temperatures in Sn-doped (7×1016 cm−3) InSb films grown on GaAs(100) substrates by MBE have been investigated with decreasing film thickness d from 1 μm. The negative MR found in weak magnetic fields for d0.5 μm can be broadly divided into two regimes: T-sensitive negative MR below Bc observed with anisotropy between parallel and perpendicular magnetic field and a T-insensitive parabolic one above Bc observable only under in-plane magnetic fields. The latter is ascribable to the skipping orbit effect due to surface boundary scattering. In vanishing magnetic fields far below Bc, the negative MR reduces with decreasing d and the different positive MR overlaps with it below 0.5 μm, eventually dominating the positive MR at d0.2 μm. These results have been analyzed using a two-layer model for the films, where the composition of the upper layer under the surface and the lower one adjacent to the InSb/GaAs interface is assumed. The MR data in the extremely weak magnetic fields below 100 G for each layer have been successfully fitted to the two-dimensional (2D) weak localization (WL) theory. These results explain that the crossover from the 2D WL to the weak anti-localization (WAL) occurs when the interface is approached with the increase of SO interaction in the layers caused by the increased influence of the asymmetric potential at the hetero interface (Rashba term) and the SO rate in the intrinsic InSb film due to the crystal field of the zinc-blende structure (Dresselhaus term) is as small as τso−13×108 s−1. 相似文献
13.
Melt-spun ribbons with composition Sm2+Y(Co0.8Fe0.1Mn0.1)17BX (X=0–1.0 and Y=0–0.2) were fabricated with a wheel speed of 50 m/s, followed by annealing in the temperature range of 500–800°C for 2.5–60 min. Our results show that all the ribbons annealed up to 800°C are composed of a TbCu7-type phase as the main phase. The highest coercivity of 8.7 kOe is obtained in a Sm-rich sample with composition Sm2.2(Co0.8Fe0.1Mn0.1)17 annealed at 750°C for 5 min. It is found that these magnets show a very promising high-temperature performance – much better than those of typical sintered 2 : 17 magnets. 相似文献
14.
In this study, Cu (II) complex/n-Si structure has been fabricated by forming a thin organic Cu (II) complex film on n-Si wafer. It has been seen that the structure has clearly shown the rectifying behaviour and can be evaluated as a Schottky diode. The contact parameters of the diode such as the barrier height and the ideality factor have been calculated using several methods proposed by different authors from current–voltage (I–V) characteristics of the device. The calculated barrier height and ideality factor values from different methods have shown the consistency of the approaches. The obtained ideality factor which is greater than unity refers the deviation from ideal diode characteristics. This deviation can be attributed to the native interfacial layer in the organic/inorganic interface and the high series resistance of the diode. In addition, the energy distribution of the interface state density (Nss) in the semiconductor band gap at Cu (II) complex/n-Si interface obtained from I–V characteristics range from 2.15 × 1013 cm−2 eV−1 at (Ec − 0.66) eV to 5.56 × 1012 cm−2 eV−1 at (Ec − 0.84) eV. 相似文献
15.
In situ atomic force microscopy (AFM) was used to study the growth behaviour of anglesite (PbSO4) monolayers on the celestite (0 0 1) face. Growth was promoted by exposing the celestite cleavage surfaces to aqueous solutions that were supersaturated with respect to anglesite. The solution supersaturation, βang, was varied from 1.05 to 3.09 (where βang = a(Pb2+) · a(SO42−)/Ksp,ang). In this range of supersaturation, two single anglesite monolayers (3.5 Å in height each) from pre-existent celestite steps were grown. However, for solution supersaturation βang < 1.89 ± 0.06, subsequent multilayer growth is strongly inhibited. AFM observations indicate that the inhibition of a continuous layer-by-layer growth of anglesite on the celestite (0 0 1) face is due to the in-plane strain generated by the slight difference between the anglesite and celestite lattice parameters (i.e. the linear misfits are lower than 1.1%). The minimum supersaturation required to overcome the energy barrier for multilayer growth gave an estimate of the in-plane strain energy: 11.4 ± 0.6 mJ/m2. Once this energy barrier is overcome, a multilayer Frank–Van Der Merwe epitaxial growth was observed. 相似文献
16.
Jong Dae Lee Dong-Hwal Lee No-Kuk Park Si Ok Ryu Tae Jin Lee 《Current Applied Physics》2006,6(6):1040
The reduction–carburization of tungsten trioxide (WO3) under carbon monoxide flow was studied in the temperature range of 300–750 °C. The reduction–carburization of WO3 was improved by mechanically mixing with zeolite-HX, -NaX and -KX. The interaction between cation in zeolite-X and oxygen in WO3 affected the improvement of the reduction–carburization of WO3 to WC. Moreover, the improved reduction–carburization of WO3 could lead to the decrease of reaction temperature. Because the particle size of WC is in contact with a reaction temperature, the nanophase WC can be prepared at low temperature. In particular, the particle size of WC was controlled by reaction temperature. The particle sizes of produced WC at 550, 650 and 700 °C were 25, 50 and 100 nm respectively. 相似文献
17.
Jun Hyung Lim Jong Hyun Shim Jun Hyuk Choi Jin Hyun Park Won Kim Jinho Joo Chan-Joong Kim 《Physica C: Superconductivity and its Applications》2009,469(15-20):1182-1185
We fabricated nano-carbon (NC) doped MgB2 bulks using an in situ process in order to improve the critical current density (Jc) under a high magnetic field and evaluated the correlated effects of the doped carbon content and sintering temperature on the phase formation, microstructure and critical properties. MgB2−xCx bulks with x = 0 and 0.05 were fabricated by pressing the powder into pellets and sintering at 800 °C, 900 °C, or 1000 °C for 30 min.We observed that NC was an effective dopant for MgB2 and that part of it was incorporated into the MgB2 while the other part remained (undoped), which reduced the grain size. The actual C content was estimated to be 68–90% of the nominal content. The NC doped samples exhibited lower Tc values and better Jc(B) behavior than the undoped samples. The doped sample sintered at 900 °C showed the highest Jc value due to its high doping level, small amount of second phase, and fine grains. On the other hand, the Jc was decreased at a sintering temperature of 1000 °C as a result of the formation of MgB4 phase. 相似文献
18.
We present a theoretical study of the collisions of atomic oxygen with O-precovered β-cristobalite (1 0 0) surface. We have constructed a multidimensional potential energy surface for the O2/β-cristobalite (1 0 0) system based mainly on a dense grid of density functional theory points by using the interpolation corrugation-reducing procedure. Classical trajectories have been computed for quasithermal (100–1500 K) and state-specific (e.g., collision energies between 0.01 and 4 eV) conditions of reactants for different O incident angles (θv). Atomic sticking and O2(adsorbed) formation are the main processes, although atomic reflection and Eley–Rideal (ER) reaction (i.e., O2 gas) are also significant, depending their reaction probabilities on the O incident angle. ER reaction is enhanced by temperature increase, with an activation energy derived from the atomic recombination coefficient (γO(θv = 0°, T)) equal to 0.24 ± 0.02 eV within the 500–1500 K range, in close agreement with experimental data. Calculated γO(θv = 0°, T) values compare quite well with available experimental γO(T) although a more accurate calculation is proposed. Chemical energy accommodation coefficient βO(T) is also discussed as a function of ER and other competitive contributions. 相似文献
19.
Xiaolian Chao Zupei Yang Xiaohui Huang Difei Ma Jinghui Zeng 《Current Applied Physics》2009,9(6):1283-1287
Effects of ZnO addition on electrical properties and low-temperature sintering of BiFeO3-modified Pb(Zr,Ti)O3–Pb(Fe2/3W1/3)O3–Pb(Mn1/3Nb2/3)O3 were investigated. The investigations revealed that the sintering temperature can be decreased to 950 °C, and the favorable properties were obtained with 0.10 wt% ZnO added ceramics. The electrical properties were as follows: d33 = 313 pC/N, Kp = 0.56, tan δ = 0.0053, εr = 1407 and Tc = 295 °C, which showed that this system was a promising material for the multilayer devices application. 相似文献
20.
L. Doyennette A. Vardi F. Guillot L. Nevou M. Tchernycheva A. Lupu R. Colombelli G. Bahir E. Monroy F.H. Julien 《Superlattices and Microstructures》2006,40(4-6):262
We have demonstrated GaN/AlN quantum dots (QD) photodetectors, relying on intraband absorption and in-plane carrier transport in the wetting layer. The devices operate at room temperature in the wavelength range 1.3–1.5 μm. Samples with 20 periods of Si-doped GaN QD layers, separated by 3 nm-thick AlN barriers, have been grown by plasma-assisted molecular-beam epitaxy on an AlN buffer on a c-sapphire substrate. Self-organized dots are formed by the deposition of 5 monolayers of GaN under nitrogen-rich conditions. The dot height is 1.2±0.6 to 1.3±0.6 nm and the dot density is in the range 1011–1012 cm−2. Two ohmic contacts were deposited on the sample surface and annealed in order to contact the buried QD layers. The dots exhibit TM polarized absorption linked to the s–pz transition. The photocurrent at 300 K is slightly blue-shifted with respect to the s–pz intraband absorption. The responsivity increases exponentially with temperature and reaches a record value of 10 mA/W at 300 K for detectors with interdigitated contacts. 相似文献