Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 5

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

Search:
in the keywords:  charge transfer
help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

Acoustically driven charge separation in semiconductor heterostructures sensed by optical spectroscopy techniques

100%
Kuryliuk V., Podolian A., Korotchenkov O.
Open Physics
|
2010
|
vol. 8
|
issue 1
65-76
EN
We demonstrate a method of using a two-layer sandwich structure, which includes a LiNbO3 plate and a semiconductor heterostructure to create an inhomogeneous stress and piezoelectric harmonic potential in the semiconductor. Both the GaAs/AlGaAs quantum well (QW) structures and SiGe/Si heterostructures are attempted, working with and without using a piezoelectric field in the semiconductor layer. The standing-wave fields generated in the semiconductor and the electron and hole distributions driven by the piezoelectric field are computed by finite element method (FEM) techniques. It is experimentally shown that, in a GaAs/AlxGa1-x As asymmetric double quantum well structure, the resonance enhancement of the narrower QW photoluminescence band is observed, which may be explained by the resonant charge transfer between the wider and narrower QWs. It is also shown that the piezoelectric fields quench the pure LO-phonon lines in the Raman spectra, whereas the coupled LO-phonon-plasmon mode strengthens. Experimental results indicate that the charge separation occurs in the plane of the QWs due to the piezoelectric fields. The recombination of carriers in the SiGe/Si heterostructures can be effectively enhanced by the presence of ultrasonic stress, displaying features consistent with varying electrical activity at dislocations.
2
Content available remote

The dependence of critical temperature on oxygen concentration in YBa2Cu3O6+x in terms of the fragmented chain model

100%
Milic M., Matic V., Lazarov N.
Open Physics
|
2011
|
vol. 9
|
issue 3
690-697
EN
An extended ASYNNNI model, that beside nearest-neighbour and next-nearest neighbour O-O interactions in the basal plane also includes interactions between the three nearest oxygen atoms, is used to describe the statistics of CuO chain fragmentation and to calculate doping and T c in YBa2Cu3O6+x . Calculations were made by the Monte Carlo method employing the recently proposed charge transfer model that assumes only chains whose length is equal to, or exceeds, a characteristic (critical) length, l cr, can provide holes to the layers and contribute to doping p. The obtained p(x) is then combined with a universal T c versus p relation to yield T c(x) characteristics that correlate remarkably with those reported in recent experiments. The best coordination between theoretical and experimental T c(x) characteristics has been achieved for l cr = 2, implying that only isolated basal plane oxygen atoms (trivial chains) do not contribute holes to CuO2 layers.
3
Content available remote

The influence of the phosphorothioate diester bond on the DNA oxidation process

88%
Karwowski B. T.
|
|
issue 1
EN
This study describes the influence of the phosphorothioate internucleotide bond on the deoxyribonucleic acid (DNA) oxidation process. The interaction of an ultraviolet radiation (UVA) with a targeted double-stranded (ds) oligonucleotide, in which one strand contains an antraquinone (AQ) moiety on the 5’-end, may lead to a hole migration process through the double helix. In the end, the migration of theformed radical cation terminates in a suitable place. Usually, this is a guanine-rich sequence. In another experiment, phosphorothioate internucleotide bonds were detected in the bacterial genome as a natural modification. In this study, a polyacrylamide gel electrophoresis (PAGE) autoradiogram analysis of irradiated ds-DNA showed that the oxidation reaction was not inhibited by an isolated guanine. Instead, irrespective of the absence or presence of a phosphorothioate bond, the termination of the ds-DNA oxidation process was predominantly observed on the thymine moieties. Based on the obtained results, it can be concluded that in the discussed case, a hole migration by a hopping mechanism is in competition with an oxidation reaction with a superoxide radical anion. Alternatively, the radical cation migration process is sequence-dependent due to its different ionization potentials. Therefore, the presence of a phosphorothioate internucleotide bond did not change the stability of ds-DNA under UVA irradiation conditions.
4
Content available remote

The role of F A1:Ag+ defects in laser light generation and coadsorption of CO and halogen atoms at the KCl and KBr surface sites. First principles calculations

63%
Abdelrazik S., Shalabi A.
Open Physics
|
2007
|
vol. 5
|
issue 4
611-636
EN
FA1:Ag+ color center at the low coordination (100) and (110) surface sites of KCl and KBr thin films play an important role in providing tunable laser oscillation and adsorbatesubstrate interactions. Double-well potentials at this site are investigated using ab initio molecular electronic structure calculations. The calculated Stokes shifted (optical transition bands), opticaloptical conversion efficiencies, the probability of orientational destruction, exciton (energy) transfer and Glasner-Tompkins empirical rule suggest that laser light generation is sensitive to (i) the lattice anion, (ii) the coordination number of surface ions, and (iii) the choice of the basis set centered on the anion vacancy. The adsorbate-substrate interactions were found to be dependent on the electronegativity of the adatom and on the lattice anion. Optimised geometries and the coadsorption of CO and (F, Cl, Br, I) on KCl and KBr (100) crystals are presented. Calculated chemisorption energies for CO on the (halogen atom/defect free sites of KCl and KBr (100) crystals) showed that the coadsorption of halogen atom tends to block other adsorbate-substrate interactions at the nearest neighbour sites. Thus if halogen atom coverage increases, the CO prefers to be adsorbed on the K+ site of the KCl and KBr (100) surfaces and on KBr relative to KCl.
5
Content available remote

Effect of Vacancies on Electronic and Magnetic Properties of Hydrogen Passivated Graphene Nanoribbons

63%
Haffad S., Benchallal L., Lamiri L., Boubenider F., Zitoune H., Kahouadji B., Samah M.
Acta Physica Polonica A
|
2018
|
vol. 133
|
issue 5
1307-1313
EN
Using first-principles calculations we have demonstrated that electronic and magnetic properties of armchair graphene nanoribbons are modified by introducing vacancies defects. The equilibrium geometries, electronic, charge spin density distributions, electronic band structures, and magnetic moments were examined in the presence of vacancies. We have found that introducing vacancies into armchair graphene nanoribbons changes the spatial distribution of neighbor atoms, particularly those located around the vacancies. Our calculations showed that the vacancies have significant effect on the magnetization of armchair graphene nanoribbons. Magnetic moment values and electronic behavior in different configurations depend on the number of vacancies. These results suggest that vacancy defects can be used to modify the electronic and the magnetic properties of armchair graphene nanoribbons.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.