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1.
The photo-current of n-ZnO/p-Si heterojunction photodiodes was improved by embedding Ag nanoparticles in the interface (ZnO/nano-PAg/p-Si), and the ratio between photo- and dark-current increased by about three orders more than that of a n-ZnO/p-Si specimen. The improvement in the photo-current resulted from the light scattering of embedded Ag nanoparticles. The IV curve of n-ZnO/p-Si degraded after thermal treatment (A-ZnO/p-Si) because the silicon robbed the oxygen from ZnO to form amorphous silicon dioxide and left an oxygen vacancy. Notably, the properties of ZnO/nano-PAg/p-Si were better in the time-dependent photoresponse under 10 V bias. Ag nanoparticles (15–20 nm) scattered the UV light randomly and increased the probability for the absorption of ZnO to enhance the properties of the photodiode.  相似文献   

2.
The dielectron widths of Y(nS)(n = 1, …, 7) and vector decay constants are calculated using the relativistic string Hamiltonian with a universal interaction. For Y(nS) (n = 1, 2, 3) the dielectron widths and their ratios are obtained in full agreement with the latest CLEO data. For Y(10580) and Y(11020) a good agreement with experiment is reached only if the 4S-3D mixing (with a mixing angle θ = 27°± 4°) and 6S-5D mixing (with θ = 40°±5°) are taken into account. The possibility to observe higher “mixed D-wave” resonances, $ \tilde \Upsilon $ \tilde \Upsilon (n 3 D 1) with n = 3, 4, 5 is discussed. In particular, $ \tilde \Upsilon $ \tilde \Upsilon (≈11120), originating from the pure 53 D 1 state, can acquire a rather large dielectron width, ∼130 eV, so that this resonance may become manifest in the e + e experiments. On the contrary, the widths of pure D-wave states are very small, Γ ee (n 3 D 1)≤ 2 eV.  相似文献   

3.
Results on the experimentally investigated dependence of the electrical resistivity of quasibinary alloys R x Y1−x Co2, where R stands for magnetic rare earth elements, on temperature (2–300 K), composition (x = 0–1), and magnetic field (0–15 T) are presented. Non-Fermi liquid behavior of electrical resistivity in a magnetic field was observed in paramagnetic Gd x Y1−x Co2 alloys. The relative magneto-thermopower of these alloys exhibits diverging behavior with decreasing temperature, indicating anomalous temperature variation of the thermopower in the non-Fermi liquid regime.  相似文献   

4.
The temperature dependences of the resistivity of single-crystal films of the Nd2 − x Ce x CuO4 + δ n-type superconductors with x = 0.14 (underdoped region) and x = 0.15 (optimal doping region) and different degrees of disorder δ have been investigated in various magnetic fields (Bc, Jab) in the temperature range 0.4–300 K. It has been demonstrated that there are differences in the behavior of the dependences of the slope of the upper critical field $ (dB_{c2} /dT)_{T \to T_c } $ (dB_{c2} /dT)_{T \to T_c } on the disorder parameter for the underdoped samples (x = 0.14) and the samples with the optimal doping (x = 0.15). The study of the dependence of the slope of the upper critical field on the degree of disorder has made it possible to discriminate experimentally between the superconductors with the d pairing and anisotropic s pairing. It has been revealed that the relative stability of the n-type superconductor with the optimal doping with respect to disordering is possibly due to the strong anisotropy of impurity scattering with symmetry of the d type.  相似文献   

5.
The electrophysical properties and structure of the nonstoichiometric high-temperature superconductor YBa2Cu3O y restored at T = 930–950°C after low-temperature decomposition (T = 200°C) into phases different in the oxygen content have been studied. It has been shown that, unlike heat treatments at T ≤ 900°C, the superconducting properties are almost completely restored for 3–5 h during grain recrystallization, which is impossible at lower temperatures. After short-term annealing at T = 930–950°C (for 1–2 h), the ceramic material still contains a significant number of structural defects, most likely, in cation sublattices. These defects can contribute to the pinning of magnetic vortices, which substantially increases the critical current density in magnetic fields up to 2 T as compared to ceramic materials produced by the conventional technology.  相似文献   

6.
Complex high-frequency (HF), σAC = σ1 ? iσ2, and static, σDC, conductivities, as well as current-voltage characteristics, have been measured in p-Si/SiGe heterostructures with a low hole density (p = 8.2 × 1010 cm?2) at temperatures T = 0.3–4.2 K in the ultraquantum limit, when the filling factor is v < 1. In order to determine the components of the HF conductivity, the acoustic contactless method in the “hybrid configuration” is used, when the surface acoustic wave propagates on the surface of the LiNbO3 piezoelectric and the heterostructure is pressed to the surface by a spring. The conductivities σ1 and σ2 are determined from the damping and velocity of the surface acoustic waves that are measured simultaneously with varying the magnetic field. The revealed HF conductivity features—σ1 ? |σ2|, the negative sign of σ2, the threshold behavior of the current-voltage characteristic, and the dependence I ∝ exp(-A/V 0.3) in the subthreshold region—indicate the formation of a pinned Wigner crystal (glass) in the ultraquantum limit (T = 0.3–0.8 K, B > 14 T).  相似文献   

7.
Corrections of order α 5 and α 6 to the hyperfine structure of S- and P-wave energy levels of the muonic-helium ion are calculated. Electron-vacuum-polarization effects, corrections for the nuclear structure, and recoil effects are taken into account. The numerical values obtained for respective hyperfine splitting, −1334.73 meV (1S), −166.64 meV (2S), −58 712.90 μeV (2P 1/2), and −24 290.69 μeV (2P 3/2), can be viewed as a reliable estimate for a comparison with experimental data, and the hyperfine-structure interval of Δ12 = 8ΔE hfs(2S) − ΔE hfs(1S) = 1.59 meV can be used to test QED predictions.  相似文献   

8.
The optical characteristics of nickel films deposited on Si(100) substrates by vacuum thermal evaporation have been studied. The thickness and optical constants of the films are determined using monochromatic zero ellipsometry, while the inverse problems are solved within the three-layer optical model of the samples. It is shown that thermal annealing leads to a change in the optical constants of nickel films in the heating-temperature range of 500–900°C. Boron carbonitride layers deposited on silicon substrates with a nickel sublayer are analyzed within multilayer optical models, which make it possible to determine the refractive index and absorption coefficient distributions along the thickness of the synthesized Si(100)/Ni/BC x N y structure.  相似文献   

9.
Cosmological models with variable G in C-field cosmology for barotropic fluid distribution in FRW space-time are investigated. To get the deterministic model of the universe, we have assumed that G=R n where R is the scale factor and n the constant. To obtain the results in terms of cosmic time t, we have assumed n=−1. We find that for n=−1, Creation field (C) and spatial volume increase with time, G and ρ (matter density) decreases with time, the model represent accelerating universe. Thus inflationary scenario exists in the model. The model is also free from horizon. The results so obtained match with the astronomical observations.  相似文献   

10.
Using the example of an easy-axis antiferromagnet with a magnetic structure of 4 z 2 x + I the effect of antisymmetric magnetoelectric interaction on the nature of the refraction of the bulk s- or p-polarized electromagnetic waves, incident from outside at any angle to the surface of the magnet, is studied analytically. The easy magnetic axis is collinear to the normal to the medium interface.  相似文献   

11.
New experimental data are presented on the effects of uniaxial compression of up to 4 kbar along the [110] and [1$ \bar 1 $ \bar 1 0] crystallographic directions on the spectra of electroluminescence and the current-voltage characteristics of diodes based on n-Al x Ga1 − x As/GaAs y P1 − y /p-Al x Ga1 − x As (y = 0.84) heterostructures that were designed for injection lasers. With increasing pressure, the spectra show a shift to shorter wavelengths, reaching 25 meV at 3 kbar; the intensity increases 2–3 times as well. Numerical calculations were carried out on the band structure of the investigated heterostructures under compression along the [110] axis, which indicate the increase in the effective band gap in the quantum well (QW) GaAs y P1 − y , with a pressure coefficient of about 8.5 meV/kbar and reduction of the barrier height at the boundaries of the QW. The calculations predict the possibility that light and heavy holes crossover at pressures above 4.5–5 kbar. The increase in the effective band gap completely describes the experimental data on the shift of the electroluminescence spectra. The mixing of light and heavy holes when approaching the band crosspoint is the probable cause of an increase in the intensity of radiation under uniaxial compression.  相似文献   

12.
We map noncommutative (NC) U(1) gauge theory on ℝ C d ×ℝ NC 2n to U(N→∞) Yang–Mills theory on ℝ C d , where ℝ C d is a d-dimensional commutative spacetime while ℝ NC 2n is a 2n-dimensional NC space. The resulting U(N) Yang–Mills theory on ℝ C d is equivalent to that obtained by the dimensional reduction of (d+2n)-dimensional U(N) Yang–Mills theory onto ℝ C d . We show that the gauge-Higgs system (A μ ,Φ a ) in the U(N→∞) Yang–Mills theory on ℝ C d leads to an emergent geometry in the (d+2n)-dimensional spacetime whose metric was determined by Ward a long time ago. In particular, the 10-dimensional gravity for d=4 and n=3 corresponds to the emergent geometry arising from the 4-dimensional N=4{\mathcal{N}}=4 vector multiplet in the AdS/CFT duality. We further elucidate the emergent gravity by showing that the gauge-Higgs system (A μ ,Φ a ) in half-BPS configurations describes self-dual Einstein gravity.  相似文献   

13.
A comparative investigation of the magnetic properties of amorphous nanogranular composites (Co41Fe39B20) x (SiO n )100 − x and (Co86Nb12Ta2) x (SiO n )100 − x has been performed in the subpercolation region at temperatures in the range 4.2–300 K. The thermomagnetic dependences in the range 4.2–300 K and the processes of magnetization reversal and remanent magnetization relaxation at liquid-helium temperatures have been studied. It has been established that the average anisotropy constants of amorphous nanograins are equal to 3.6–7.0 kJ/m3 for the (Co41Fe39B20) x (SiO n )100 − x composites and 5–8 kJ/m3 for the (Co86Nb12Ta2) x (SiO n )100 − x composites. The fundamental differences in the concentration dependences of the anisotropy constant K eff and the coercive force H C have been revealed for the two systems under investigation. It has been demonstrated that, as the concentration of the metal phase increases, the quantities K eff and H C increase for the (Co86Nb12Ta2) x (SiO n )100 − x composites and decrease for the (Co41Fe39B20) x (SiO n )100 − x composites.  相似文献   

14.
The specific features of the variation in the thermoelectric figure-of merit Z for p-type bismuth- and antimony-chalcogenide-based solid solutions p-(Bi,Sb)2(Te,Se)3 have been analyzed with allowance made for the data amassed in the investigation of thermoelectric and galvanomagnetic properties. It has been shown that, in the samples with optimum carrier concentrations, the increase in Z in the multicomponent p-Bi2 − x Sb x Te3 − y Se y composition (x = 1.3, y = 0.06) in the temperature range 300–370 K is mediated by the high carrier mobility and the low lattice thermal conductivity. The higher effective mass of the density of states and the larger slope of the temperature dependence of the mobility as compared to the other compositions bring about an increase in Z in the p-Bi2 − x Sb x Te3 solid solution for x = 1.6 in the temperature range 370–550 K. The increase in the figure-of merit reached in the compositions under study stems also from the increasing contraction of constant-energy ellipsoids along the binary and bisector directions and from the change in the angle θ between the principal axes of the ellipsoids and the crystallographic axes.  相似文献   

15.
We obtain exact results in α′ for open and closed A-model topological string amplitudes on a large class of toric Calabi-Yau threefolds by using their correspondence with five dimensional gauge theories. The toric Calabi-Yaus that we analyze are obtained as minimal resolution of cones over Y p,q manifolds and give rise via M-theory compactification to SU(p) gauge theories on . As an application we present a detailed study of the local case and compute open and closed genus zero Gromov-Witten invariants of the orbifold. We also display the modular structure of the topological wave function and give predictions for higher genus amplitudes. The mirror curve in this case is the spectral curve of the relativistic A 1 Toda chain. Our results also indicate the existence of a wider class of relativistic integrable systems associated to generic Y p,q geometries.  相似文献   

16.
A method of calculating the effective deformation-potential constant E 1 for holes and longitudinal acoustic phonons in isotropic polycrystalline silicon is suggested. The deformation-potential constant E 1 is estimated through the deformation potentials a, b, and d of the silicon single crystal. The procedure of averaging of the squared modulus of the hole and acoustic phonon interaction Hamiltonian written in the plane wave basis over the polycrystal ensemble provides the basis for calculation of the constant E 1 . It is demonstrated that for T = 200–600 K, hole concentration p = (5.0–10.0)∙1019 cm–3, and crystallite size d = 300–3000 ?, the deformationpotential constant E 1 is independent of the hole concentration p, temperature T, and crystallite size d.  相似文献   

17.
New experimental data on inclusive cross section of neutral-vector-meson (ω 0, ϕ, K S 0) production in proton-proton collisions at = 200 GeV obtained at RHIC are analyzed in the framework of z scaling. Properties of z-presentation are used to predict hadron yields over a wide range of transverse momentum p T and collisions energy . The next-to-leading-order perturbative QCD calculations of inclusive cross sections of π 0 mesons produced in pp and collisions over a wide range of and p T are compared with ISR, S pS, RHIC data and predictions of z scaling. The dependence of the spectra in p T and z presentations for different parton distribution and fragmentation functions is studied. The sensitivity of the obtained results to the choice of the renormalization (μ R ), initial-state factorization (μ F ), and final-state factorization (fragmentation) (μ H ) scales is verified. It is shown that self-similar features of particle production dictated by the z scaling give strong restriction on the asymptotic behavior of the inclusive spectra in high-p T region. The text was submitted by the author in English.  相似文献   

18.
The spectra of kinetic energies of positive Si n O m + cluster ions (n = 2–5, m = 2–7) have been measured using a double focusing ion microanalyzer with reverse geometry at instants 10−5 to 10−4 s after emission. The dissociation energies have been determined within the evaporative ensemble model and the theory of unimolecular decay reactions. The results obtained are compared with the binding energies of neutral Si n O m clusters.  相似文献   

19.
Restricted active space (RAS) configuration interaction (CI) approach is employed to compute the P,T-odd interaction constant W d for the ground (2Σ1/2) state of YbF molecule. The present estimate of W d = −1.164 × 1025 Hz/e-cm is expected to provide a reliable limit on the electron’s electric dipole moment (EDM), d e.  相似文献   

20.
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