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1.
In this paper, we report on all the electro-optic coefficients of the low-symmetry crystal YbCa 4O(BO 3) 3 measured by the interferometric method. The new sample orientations, which have not been reported so far, have been used for measuring the skew electro-optic coefficients γ 51, γ 53, γ 42 and γ 62 independently. The results obtained are γ 11=0.6, γ 21=0.4, γ 31=0.3, γ 13=0.3, γ 23=0.2, γ 33=2.2, γ 51=0.9, γ 53=4.1, γ 42=0.8 and γ 62=0.4×10 −12 m/V. 相似文献
2.
In this paper, we report all of the electro-optic coefficients of the low symmetry crystal GdCa 4O(BO 3) 3 measured by the interferometric method. The new sample orientations, which have not been reported so far, have been used for measuring the skew electro-optic coefficients γ 51, γ 53, γ 42 and γ 62 independently. The results obtained are γ 11=0.4, γ 21=0.5, γ 31=0.6, γ 13=0.1, γ 23=0.4, γ 33=2.0, γ 51=0.7, γ 53=1.5, γ 42=0.5, γ 62=0.8×10 −12m/V. 相似文献
3.
We report on the formation technique of single-crystalline β-FeSi 2 balls (<100 nm) embedded in a Si p–n junction region by Si molecular beam epitaxy (MBE). β-FeSi 2 films grown on Si (0 0 1) by reactive deposition epitaxy (RDE) aggregated into islands after annealing at 850°C in ultrahigh vacuum. The islands of β-FeSi 2 aggregated further into a ball shape by following the Si MBE overgrowth at 750°C. It was found from X-ray diffraction (XRD) patterns that the epitaxial relationship between the two materials, and single-crystalline nature were preserved even after the annealing and the Si overgrowth. Capacitance–voltage ( C– V) characteristics and transmission electron microscope (TEM) images revealed that a lot of defects were introduced around the embedded β-FeSi 2 balls with an increase of embedded β-FeSi 2 quantity. 相似文献
4.
Microalloying additions of Ag (0.1 at.%) increase the hardening response of Al–Zn–Mg alloys to elevated temperature ageing in the range 100–200°C due to the formation of a high density of very fine η′ precipitate plates. The present study employed transmission electron microscopy (TEM) and three-dimension atom probe (3DAP) to study the early stages of ageing in the alloy Al–1.8Zn–3.4Mg–0.1Ag (at.%) in an attempt to identify the role of Ag in stimulating precipitation hardening. During isothermal ageing at 90°C, the hardening response is attributed to a high density of Zn–Mg–Ag rich solute clusters and GP zones. During ageing at 150°C, η′ precipitates nucleate at Zn–Mg–Ag rich solute clusters, the former growing as {111} platelets with an average composition of approximately 20 at.% Zn, 20 at.% Mg and 1.4 at.% Ag. The 3DAP data indicates that the co-segregation of Zn and Ag and subsequently Zn and Mg atoms precedes the formation of the Zn–Mg–Ag rich solute clusters. The GP zones and η′ precipitates were observed to possess a Zn:Mg ratio close to 1:1, whereas the equilibrium η precipitates possessed compositions consistent with MgZn 2. Furthermore, partitioning of Ag was observed inside all precipitate phases, viz. G.P. zones, η′ and η. 相似文献
5.
We report measurements of anamolously large dissipative conductivities, σ 1, in Bi 2Sr 2CaCu 2O 8+δ at low temperatures. We have measured the complex conductivity of Bi 2Sr 2CaCu 2O 8+δ thin films at 100–600 GHz as a function of doping from the underdoped to the overdoped state. At low temperatures there exists a residual σ 1 which scales with the T=0 superfluid density as the doping is varied. This residual σ 1 is larger than the possible contribution to σ 1 from a thermal population of quasiparticles (QP) at the d-wave gap nodes. 相似文献
6.
Diffusion of dysprosium on the (1 1 1) facet of a tungsten micromonocrystal was investigated by means of spectral analysis of field emission current fluctuations. The experimental spectral density functions of the current fluctuations were analysed by using Gesley and Swanson’s theoretical spectral density function, which enables to determine the surface diffusion coefficient D for dysprosium. Derived from the temperature dependence of D, the diffusion activation energy E is presented for some Dy coverages θ(1 1 1). In the temperature range 400–600 K, the E first drops from 1.25 eV per atom at θ (111)≈0.25 ML to 0.48 eV per atom at θ (111)≈1 ML (corresponding to the minimum of the work function of the system), then increases to 1.03 eV per atom at θ (111)≈1.3 ML. The results are discussed from the aspects of the substrate structure and interaction in the adsorbed layer. 相似文献
7.
The a.c. conductivity behaviour in the 20–300 K temperature range has been investigated for (Ag 2S) x(AgPO 3) 1−x and (Ag 2SO 4) x(AgPO 3) 1−x glasses at various salt contents ( x). The temperature dependence at selected frequencies in the radioand micro-wave region displays several relaxational contributions which are indistinct in the frequency domain. The low temperature experimental data are discussed and a proposed ‘new universality’ has been examined. 相似文献
8.
D 2 temperature-programmed desorption (TPD) was used to probe the structure of the Si(011)-(16 × 2) surface. Deuterium was adsorbed at 200°C to coverages θ D ranging up to complete saturation (approximately 1.1 ML) and the sample heated at 5°C s −1. TPD spectra exhibited three second-order desorption peaks labelled β 2, β* 1 and β 1 centered at 430, 520 and 550°C. Of the proposed models for the Si(011)-(16 × 2) reconstruction, the present TPD results as a function of θ D provide support for the adatom/dimer model with the β 2 peak assigned to D 2 desorption from the dihydride phase, while the β* 1 and β 1 peaks arise from adatom and surface-atom monohydride phases. 相似文献
9.
Superfluidity of Λ hyperons in neutron star cores is investigated by a realistic approach to use reliable ΛΛ interactions and the effective mass of Λ based on the G-matrix calculations. It is found that Λ superfluid can exist at - ( t d) with t - 2 0( 0 being the nuclear density) and d - (3 – 4.5) 0, depending on hyperon core models. 相似文献
10.
Ti substituted BiFe 1−xTi xO 3+δ films have been prepared on indium–tin oxide (ITO)/glass substrates by the sol–gel process. The films with x=0.00–0.20 were prepared at an annealing temperature of 600 °C. X-ray diffraction patterns indicate that all films adopt R3m structure and the films with x=0 and 0.10 show pure perovskite phase. Cross-section scanning shows the thickness of the films is about 300 nm. Through 0.05 Ti substitution, the 2 Pr increases to 8.30 μC/cm 2 from 2.12 μC/cm 2 of the un-substituted BiFeO 3 film and show enhanced ferroelectricity at room temperature. The 2 Pr values are 2.63 and 0.44 μC/cm 2 for the films with x=0.01 and 0.2, respectively. Moreover, the films with x=0.05 and 0.10 show enhanced dielectric property since the permittivity increases near 150 at the same measuring frequency. Through the substitution of Ti, the leakage conduction is reduced for the films with x=0.05–0.20. 相似文献
11.
[Fe(0.5 nm)/Pt(0.5 nm)] 40, [Fe(1 nm)/Pt(1.5 nm)] 20 and [Fe(3 nm)/Pt(3 nm)] 10 multilayer were prepared by DC magnetron sputtering. By conventional furnace annealing (CA) at 270–600 °C for various time, all of the films still remained the disordered structure with the soft magnetic phase. By rapid thermal annealing (RTA) at 500 °C for various time, we obtained the [Fe(1 nm)/Pt(1.5 nm)] 20 and [Fe(3 nm)/Pt(3 nm)] 10 films with L1 2 ordered FePt 3 phase which was almost ferromagnetic at room temperature. However, the [Fe(0.5 nm)/Pt(0.5 nm)] 40 films was still disordered state even under RTA. Compared with CA, RTA exposed an outstanding effect on accelerating the phase transition when the film thickness is over [Fe(0.5 nm)/Pt(0.5 nm)] 40. 相似文献
12.
This study was conducted to investigate the ultraweak delayed radiochemiluminescence (RCL) spectra, kinetics and spectroscopic properties of humic acids (HAs) after γ-radiation exposure (absorbed doses of 1−10 kGy, Co-60) in model systems. The kinetics and spectral distribution of RCL (340–650 nm) were measured using the single photon counting (SPC) method and cut-off filters. The intensity of fluorescence (λex=390, 440, 490 and 540 nm) covering the spectral range 400–580 nm was heavily dependent on the λex and slightly increased with the absorbed dose of γ-radiation. Absorption spectra (the range 240−800 nm) and color coefficients E2.6/4 and E4/6 of irradiated solutions indicated that post-radiative degradation/polymerization processes take place in the HA, changing their macromolecule size or properties. Comparison of FTIR spectra and elemental analysis proved an increased O and decreased C atoms in irradiated samples. The data indicate on the radiolysis-induced degradation of native HA into fulvic-like acids with higher hydrophilicity and lower molecular size. 相似文献
13.
Anomalies are found in the near-band-edge luminescence properties of Δ 2-light-hole indirect excitons in Si 1−yC y-based tensilely strained quantum wells (QWs). The experimental spectra exhibit a clear signature of phonon-assisted transitions on the lower energy side of the “no-phonon” transition, which indicates the relevance of “virtual” indirect valleys and in-plane k-dispersion, as opposed to the theoretical prediction that the zone-centered Δ 2 valleys take over the conduction band edge. Intervalley scattering between [0 0 1]-Δ 2 valleys and in-plane Δ 4 valleys is suggested as the underlying mechanism. On the other hand, the experimental evidence was found for “apparently enhanced” quantum-confined Stark red shifts for Si 1−yC y-based QWs. However, quantitative estimates are in conflict with the experimental results and predict a blue shift due to exciton weakening which masks the Stark effect as in the case of Δ 4-heavy hole excitons in Si 1−xGe x-based QWs. 相似文献
14.
Materials from the Mn (0.5−x)Ca xTi 2(PO 4) 3 (0≤ x≤0.50) solid solution were obtained by solid-state reaction in air at 1000 °C. Selected compositions were investigated by powder X-ray diffraction analysis, 31P nuclear magnetic resonance (NMR) spectroscopy and electrochemical lithium intercalation. The structure of all samples determined by Rietveld analysis is of the Nasicon type with the R
space group. Mn 2+/Ca 2+ ions occupy only the M1 sites in the Ti 2(PO 4) 3 framework. The divalent cations are ordered in one of two M1 sites, except for the Mn 0.50Ti 2(PO 4) 3 phase, where a small departure from the ideal order is observed by XRD and 31P MAS NMR. The electrochemical behaviour of Mn 0.50Ti 2(PO 4) 3 and Mn (0.5−x)Ca xTi 2(PO 4) 3 phases was characterised in Li cells. Two Li ions can be inserted without altering the Ti 2(PO 4) 3 framework. In the 0≤ y≤2 range, the OCV curves of Li//Li yMn 0.50Ti 2(PO 4) 3 cells show two main potential plateaus at 2.90 and 2.50–2.30 V. Comparison between the OCV curves of Li//Li (1+y)Ti 2(PO 4) 3 and Li//Li yMn 0.50Ti 2(PO 4) 3 shows that the intercalation occurs first in the unoccupied M1 site of Mn 0.50Ti 2(PO 4) 3 at 2.90 V and then, for compositions y>0.50, at the M2 site (2.50–2.30 V voltage range). The effect of calcium substitution in Mn 0.50Ti 2(PO 4) 3 on the lithium intercalation is also discussed from a structural and kinetic viewpoint. In all systems, the lithium intercalation is associated with a redistribution of the divalent cation over all M1 sites. In the case of Mn 0.50Ti 2(PO 4) 3, the stability of Mn 2+ either in an octahedral or tetrahedral environment facilitates cationic migration. 相似文献
15.
The inhibitory activities, sulfhydryl bonds and far-UV circular dichroism (CD) spectra of Kunitz and Bowman–Birk soybean trypsin inhibitors (KTI and BBTI) were measured before and after ultrasound treatments. The differences between KTI and BBTI in conformation changes and resistance to ultrasound were observed. The secondary structures of KTI were found to be composed of β-sheet (22.5%), β-turn (16.2%) and random coils (61.4%) while that of BBTI composed of only β-sheet (52.6%) and random coils (47.4%). KTI lost its inhibitory activity more quickly than BBTI, proportionally to the ultrasound amplitudes and sonication durations used. Relevant synchronous phenomena observed included the inactivation of KTI, significant rise in sulfhydryl content and corresponding conformation changes, in which there were dramatic decreases in both β-turn and random coil contents and increase in the β-sheet structure over the entire sonication duration and ultrasonic amplitude scale used by the study. Ultrasound affected the activities and conformations of KTI and BBTI by exerting an influence on their disulfide bonds. For KTI, up to 55% of inhibitory activity could be inactivated, at which about 71.5% of disulfide bonds were altered and the [ θ] 200nm value was changed from native −2545 deg cm 2 dmol −1 to −1827 deg cm 2 dmol −1. Whereas for BBTI, far-UV CD spectra, β-sheet and random structures were barely affected, only about 5.29% of disulfide bonds were found altered and the [ θ] 200nm value was changed only from native −797 deg cm 2 dmol −1 to −700 deg cm 2 dmol −1. It is concluded that ultrasound inactivates KTI by inducing a reduction in the disulfide bonds and then changes the conformations. 相似文献
16.
We study theoretically the Co magnetization suppression at the Co–M (M=Ti, Nb, Mo, Re, Os, Ir and Pt) interface. We consider (1) M(1×1) overlayer on the FCC(1 1 1) or HCP(0 0 0 1) slab, (2) c(2×2) Co–M alloy above the same surfaces. In the latter case, the Co magnetization is reduced to about 0.5 μ B by Ti, Nb, Mo and Re, but the effect is probably an overestimation because of compression of M–Co bonds. At Co atoms below the M(1×1) overlayer, the Co magnetization does not drop below 1 μ B. We discuss also the Co–M antiferromagnetic coupling. 相似文献
17.
A series of apatite-type La–Ge–O ceramics were prepared and their cation-defect at the 4f+6h sites and oxide ion-defect at 2a site were investigated. In La xGe 6O 12+1.5x ceramics of x=6–12, the higher conductivities were obtained in the region of apatite composition, La x(GeO 4) 6O 1.5x−12 ( x=8–9.33), and the highest conductivity was achieved for La 9(GeO 4) 6O 1.5 ( x=9), where the number of cation (La 3+) occupying the 4f+6h sites is 9 and the number of oxide ion occupying the 2a site is 1.5. The ceramics with cation- and oxide ion-defects were La 9−0.66xSr x(GeO 4) 6O 1.5 ( x=0–1), La 9−1.33xZr x(GeO 4) 6O 1.5 ( x=0–1), La 9−xSr x(GeO 4) 6O 1.5−0.5x ( x=0–3), La 9−xZr x(GeO 4) 6O 1.5+0.5x ( x=0–1), La x(GeO 4) 3x−21(AsO 4) 27−3xO 1.5 ( x=0–3), La x(GeO 4) 33−3x(AlO 4) 3x−27O 1.5 ( x=0–3), La 9(GeO 4) 6−x (AlO 4) xO 1.5−0.5x ( x=0–3), La 9(GeO 4) 6−x(AsO 4) xO 1.5+0.5x ( x=0–1), La 9.33−xSr x(GeO 4) 6O 2−0.5x ( x=0–1.2) and La x(GeO 4) 4.5(AlO 4) 1.5O 1.5x−12.75 ( x=8.8–9.83), which were prepared by the partial substitution of La 3+and GeO 44−of the basic apatite La 9(GeO 4) 6O 1.5 with Sr 2+ or Zr 4+ and AlO 45− or AsO 43−. Such substitutions lowered the conductivity of La 9(GeO 4) 6O 1.5. These results were discussed by the electrostatic interaction between Sr 2+, Zr 4+, AlO 45− or AsO 43− and oxide ion as a conductive species. 相似文献
18.
Self-assembly of β-Ga 2O 3 (beta-gallium oxide) nanobelts with diameters of 50–100 nm and lengths of tens to hundreds of microns have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Under appropriate conditions such as nanobelts concentration, controlled solvent evaporation, β-Ga 2O 3 nanobelts assemble into a fan-like structure on the substrate. A tendency of these nanobelts to align parallel to each other was also observed. The mechanism behind the formation of self-assembly of β-Ga 2O 3 nanobelts has been proposed on the basis of lateral capillary forces. 相似文献
19.
The structural and optical properties of β-FeSi 2 precipitates produced by ion beam synthesis have been investigated by transmission electron microscopy, photoluminescence (PL) analysis and near infrared transmission measurements. The PL spectrum of β-FeSi 2 precipitates in a dislocation free sample has been observed to consist of a sharp line at 1.54 μm and a weak peak at 1.46 μm. Optical transmission measurements showed a direct band gap about 0.8 eV smaller than in continuous β-FeSi 2 film. Calculation of the electronic bands of β-FeSi 2 for different values of the lattice parameters indicates that this reduction can be ascribed to band distortion provided by the lattice strain. 相似文献
20.
We consider one-dimensional photonic crystals made of alternating layers of two kinds of isotropic chiral media. The two layers are characterized by the dielectric permittivities ε 1 and ε 2, the magnetic permeabilities μ 1 and μ 2, the chirality parameters γ 1 and γ 2 and the thicknesses d1 and d2. By diagonalizing an 8 × 8 matrix derived from the two coupled wave equations satisfied by our system, we obtain exact analytical expressions for the dispersion relation for plane electromagnetic waves propagating at an arbitrary angle with respect to the layers. We present a detailed analysis of our dispersion relation and explore the evolution of the photonic band structure as the frequency, the chirality parameter and the incident angle vary, with a special emphasis on the generation of the cross- and co-polarization bandgaps. 相似文献
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