排序方式: 共有119条查询结果,搜索用时 15 毫秒
111.
Both electrical and optical activation studies of Si-implanted Al0.18Ga0.82N have been made as a function of anneal time and anneal temperature to obtain maximum possible electrical activation efficiency. Silicon ions were implanted at 200 keV with doses of 5×1014 and 1×1015 cm−2, and the samples were annealed from 1100 to 1250 °C for 5-25 min with a 500 Å thick AlN cap in a nitrogen environment. The electrical activation efficiency and Hall mobility increase with anneal time and anneal temperature. Nearly 100 and 95% electrical activation efficiencies were obtained for Si-implanted Al0.18Ga0.82N with doses of 5×1014 and 1×1015 cm−2 and annealing at 1250 and 1200 °C for 25 min, respectively. The photoluminescence measurements show an excellent implantation damage recovery after annealing at these optimum anneal conditions, showing a strong near band emission. These optical results correlate well with the electrical results. 相似文献
112.
Nitrogen-doped TiO2 (N-TiO2) films were prepared by low-energy implantation of nitrogen ions into pulsed laser deposited anatase TiO2 films. The anatase phase of the films was not changed by the implantation with very low energy of 200 eV. XPS measurements revealed that the implanted nitrogen species were mainly interstitial ones. The nitrogen concentration was increased with increasing ion flux which could be controlled by adjusting the gas flow rate of the ion source. All the produced N-TiO2 films exhibited visible-light photocatalytic activities in degradation of methylene blue in aqueous solutions, indicating that interstitial nitrogen could also be responsible for the photocatalysis in visible region. Higher visible-light photocatalytic efficiency was achieved with higher implanted nitrogen concentration. 相似文献
113.
Cd1−xMnxS nano-crystalline films (0 ≤ x ≤ 0.5) were formed on glass substrates by thermal evaporation technique at room temperature (300 K). AFM studies showed that all the films were in nano-crystalline form with the grain size varying in the range between 36 and 58 nm and exhibited hexagonal structure of the host material. The lattice parameters varied linearly with composition, following Vegard's law in the entire composition range. The nanohardness and Young's modulus decreased sharply with ‘Mn’ content upto x = 0.3 and increased with high Mn content. 相似文献
114.
Soumen Das 《Applied Surface Science》2007,253(21):8661-8668
ZnO-Al2O3 nanocomposite thin films were prepared by sol-gel technique. The room temperature synthesis was mainly based on the successful peptization of boehmite (AlO(OH)) and Al(OH)3 compounds, so as to use it as matrix to confine ZnO nanoparticles. The relative molar concentrations of xZnO to (1 − x) Al2O3 were varied as x = 0.1, 0.2 and 0.5. The optical absorption spectra of the thin films showed intense UV absorption peaks with long tails of variable absorption in the visible region of the spectra. The ZnO-Al2O3 nanocomposites thin films were doped with MgO by varying its molar concentrations as y = 0.05, 0.75, 0.1, 0.125, 0.15 and 0.2 with respect to the ZnO present in the composite. The MgO doped thin films showed suppression of the intense absorption peaks that was previously attained for undoped samples. The disappearance of the absorption peaks was analyzed in terms of the crystalline features and lattice defects in the nanocomposite system. The bulk absorption edge, which is reportedly found at 3.37 eV, was shifted to 5.44 eV (for y = 0.05), 5.63 eV (for y = 0.075) and maximum to 5.77 eV (for y = 0.1). In contrast, beyond the concentration, y = 0.1 the absorption edges were moved to 5.67 eV (for y = 0.125), 5.61 eV (for y = 0.15) and to 5.49 eV (for y = 0.2). This trend was explained in terms of the Burstein-Moss shift of the absorption edges. 相似文献
115.
116.
A theoretical analysis of fractional anomalous diffusion caused by an instantaneous point source in disordered fractal media is studied. Using the method of symmetry group of scaling transformations and the H-function, the analytical solutions of concentration distribution are given. At the same time we derive the expressions of scattering function spectrum.The result shows that the scattering function spectra still have the properties of scaling function. The scattering functions of point source, line source and area source in regular Euclidean space can be regarded as particular cases of this paper and are included in this paper. At the end of the paper we discuss the asymptotic behaviors of the solution in detail. The results of this paper can be taken to be the fundamental solutions for every kind of boundary value problems of fractional anomalous diffusion in disordered fractal media. 相似文献
117.
J.M. Polson I. Vattulainen H. Zhu M.J. Zuckermann 《The European physical journal. E, Soft matter》2001,5(4):485-497
We employ off-lattice Monte Carlo simulations to study lateral diffusion in lipid-sterol bilayers using a two-dimensional
model system which has been designed to simulate the experimental phase diagrams of both lipid-cholesterol and lipid-lanosterol
systems. We focus on the effects of varying sterol concentration and temperature on the tracer diffusion coefficient, D, which characterizes the lateral motion of single tagged lipids in a bilayer. Generally, we find that increasing the cholesterol
concentration suppresses D due to an increased conformational ordering of lipid chains. We argue that this effect competes with an increase in the average
free area per lipid, which favours an increase in D. At temperatures close to the main transition temperature, the competition between the two effects leads to intriguing behavior
of D. Overall, the model results are in excellent qualitative agreement with available experimental results for lipid-cholesterol
mixtures. Additional studies of a model lipid-lanosterol system, for which experimental diffusion results are not available,
predict that the presence of lanosterol has a smaller effect than cholesterol on reducing D relative to the pure lipid system. We conclude that the molecular model employed contains the essential features required
to describe many of the qualitative features of the lateral diffusion behavior in lipid-sterol systems.
Received 24 November 2000 and Received in final form 30 April 2001 相似文献
118.
V.Yu. Grishina L.A. Kondratyuk W. Cassing A.B. Kaidalov E. De Sanctis P. Rossi 《The European Physical Journal A - Hadrons and Nuclei》2001,10(3):355-364
We investigate deuteron two-body photodisintegration within the framework of the Quark-Gluon Strings Model with nonlinear
baryon Regge trajectories. Special attention is paid to the use of QCD motivated Regge trajectories of the logarithmic and
square-root form. We find that the recent experimental data from TJNAF in the few-GeV region can be reasonably described by
the model. Angular distributions at different γ-energies are presented and the effect of a forward-backward asymmetry is discussed.
Predictions for the energy dependence of dσ/dt at higher energies and different Θc.m. are presented, too.
Received: 12 March 2001 / Accepted: 19 March 2001 相似文献
119.
chemical effect on the neutral species; and (ii) a Fermi-level effect on the ionized species, because, in addition to the chemical effect, the solubility of the species also has a dependence
on the semiconductor Fermi-level position. For Zn and Be in GaAs and related compounds, their diffusion process is governed
by the doubly-positively-charged group III element self-interstitials (I2+
III), whose thermal equilibrium concentration, and hence also the diffusivity of Zn and Be, exhibit also a Fermi-level dependence,
i.e., in proportion to p2. A heterojunction consists of a space-charge region with an electric field, in which the hole concentration is different
from those in the bulk of either of the two layers forming the junction. This local hole concentration influences the local
concentrations of I2+
III and of Zn- or Be-, which in turn influence the distribution of these ionized acceptor atoms. The process involves diffusion and segregation
of holes, I2+
III, Zn-, or Be-, and an ionized interstitial acceptor species. The junction electric field also changes with time and position.
Received: 20 August 1998/Accepted: 23 September 1998 相似文献