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Wyświetlanie 1-15 z 114
Tytuł:
Exact diagonalization approach for atomistic calculation of piezoelectric effects in semiconductor quantum dots
Autorzy:
Świderski, M.
Zieliński, M.
Powiązania:
https://bibliotekanauki.pl/articles/1075363.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
Opis:
We present an exact diagonalization approach for atomistic calculation of excitonic properties of semiconductor nanostructures under piezoelectric field. The method allows for efficient treatment of both single particle and many-body states at a small computational cost and results in a very good agreement with the full diagonalization treatment. We illustrate our approach by analyzing the effect of a piezoelectric field on a spectra of a self-assembled InAs/GaAs lens-shaped quantum dot. We study the influence of linear and quadratic piezoelectric terms on the quantum dot electronic structure and importantly we found that the non-linear, density functional based theory of piezoelectricity produces results very similar to those obtained by a well-established linear approach utilizing empirical parameters.
Źródło:
Acta Physica Polonica A; 2016, 129, 1a; A-79-A-82
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin-Dependent Coupling of Charged Quantum Dot Excitons with Continuum States
Autorzy:
Urbaszek, B.
Warburton, R. J.
Karrai, K.
Schulhauser, C.
Högele, A.
McGhee, E. J.
Govorov, A. O.
Gerardot, B. D.
Marie, X.
Amand, T.
Petroff, P. M.
Powiązania:
https://bibliotekanauki.pl/articles/2038350.pdf
Data publikacji:
2004-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
Opis:
Magnetic field and temperature dependent photoluminescence studies on neutral and charged excitons in individual InAs quantum dots allow us to uncover different mechanisms by which the discrete quantum dot states are coupled to delocalized continuum states in a quantum well (the wetting layer). The behaviour of the neutral and singly charged excitons can be explained taking only discrete quantum dot states into account. For doubly and triply charged excitons we have to consider spin dependent coherent and incoherent interactions between discrete quantum dot states and delocalized wetting layer states.
Źródło:
Acta Physica Polonica A; 2004, 106, 3; 395-402
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of Tool Tilt Angle on 1050 Aluminum Lap Joint in Friction Stir Welding Process
Autorzy:
Barlas, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1031715.pdf
Data publikacji:
2017-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Vj
87.15.La
Opis:
In this paper, the effect of tool tilt angle on tensile-shear failure load and weld zone properties for 1050 aluminum plates, welded by friction stir lap welding, were investigated. For this purpose, tool tilt angle was varied from 0° to 5° under the constant other parameters, such as tool geometry, tool rotation speed of 1200 rpm and tool travel speed of 30 mm/min. The tensile-shear test was employed to test the mechanical properties of the joint. Optical microscope examinations, microhardness and temperature measurements were also performed in weld zone of lap joints. According to overall results, the tool tilt angle has a reasonable influence on the joint soundness and weld defect formation. If the tool axis was perpendicular to plate surface or a larger tool tilt angle was used, such configurations had harmful effect for the weld zone. In such case the tensile-shear failure load dropped from 4853 N to 2799 N. Recorded peak temperatures varied from 381°C to 438°C in the weld center. The measured mean hardness values of the stir and heat-affected zones were 31.5 HV and 28.3 HV, respectively, which are lower than that of aluminum 1050 base metal (40.7 HV).
Źródło:
Acta Physica Polonica A; 2017, 132, 3; 679-681
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Magnetic Field on Dark States in Transport through Triple Quantum Dots
Autorzy:
Wrześniewski, K.
Weymann, I.
Powiązania:
https://bibliotekanauki.pl/articles/1032454.pdf
Data publikacji:
2017-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.23.-b
73.21.La
Opis:
We theoretically study the electronic transport through a triple quantum dot system in triangular geometry weakly coupled to external metallic leads. By means of the real-time diagrammatic technique, the current and Fano factor are calculated in the lowest order of perturbation theory. The device parameters are tuned to such transport regime, in which coherent population trapping of electrons in quantum dots due to the formation of dark states occurs. The presence of such states greatly influences transport properties leading to a strong current blockade and enhanced, super-Poissonian shot noise. We consider both one- and two-electron dark states and examine the influence of magnetic field on coherent trapping in aforementioned states. When the system is in one-electron dark state, we observe a small shift of the blockade's region, whereas in the case of two-electron dark state, we show that strong magnetic field can lift the current blockade completely.
Źródło:
Acta Physica Polonica A; 2017, 132, 1; 108-111
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of retrapping on thermoluminescence peak intensities of small amorphous silicon quantum dots
Autorzy:
Debelo, N.
Dejene, F.
Mal'nev, V.
Senbeta, T.
Mesfin, B.
Roro, K.
Powiązania:
https://bibliotekanauki.pl/articles/1070477.pdf
Data publikacji:
2016-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
73.63.Kv
Opis:
The effect of retrapping on thermoluminescence intensity peak corresponding to each trap of small amorphous silicon quantum dots in three traps - one recombination center model is investigated. For first order kinetics, where there is no effect of retrapping, the thermoluminescence intensity clearly depends on the level of the trap beneath the edge of the conduction band. This energy difference between the edge of the conduction band and the level of the trap is called trap depth (activation energy). The shallowest trap gives the highest thermoluminescence intensity peak for first order kinetics. However, it was clearly observed that for second order and a case beyond second order kinetics, the thermoluminescence intensity peak corresponding to each trap does not depend on the trap depth. In this case, the retrapping probability coefficients are taken into account and most electrons which are detrapped from the shallow trap(s) will be retrapped to the deeper trap(s) resulting in fewer electrons taking part in the recombination process. This significantly reduces the thermoluminescence intensity peaks of the shallower trap(s). It was observed that the deepest trap, with very high concentration of electrons due to the retrapping phenomenon, gives the highest thermoluminescence intensity. In addition, the variation of concentration of electrons in each trap and the intensity of the thermoluminescence are presented. Though we considered the model of three traps and one recombination center, this phenomenon is true for any multiple traps.
Źródło:
Acta Physica Polonica A; 2016, 129, 3; 362-366
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Energy Band and Absorption Coefficient of Quantum Dots in a Well Structure
Autorzy:
Zhang, P.
Lu, X.
Zhang, C.
Yao, J.
Powiązania:
https://bibliotekanauki.pl/articles/1419887.pdf
Data publikacji:
2012-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
73.63.Kv
Opis:
Building on the effective-mass envelope function theory, this paper focuses on the study of the energy band and the absorption coefficient of $InAs//In_{x}Ga_{1 - x}As$ quantum dots in a well (DWELL) structure. In contrast to $InAs//In_{0.15}Ga_{0.85}As$ quantum DWELL, the $InAs//In_{0.2}Ga_{0.8}As$ quantum DWELL has lower ground states. With the thickness of $In_{0.15}Ga_{0.85}As$ layer changing from 7 nm to 9 nm and $In_{0.2}Ga_{0.8}As$ layer changing from 9 nm to 12 nm, the calculation shows that their absorption coefficient spectra takes a red shift in the long-wave infrared and far-infrared ranges, respectively. Moreover, when the thickness of the $In_{x}Ga_{1 - x}As$ layer is defined as 9 nm, the absorption coefficient spectra of $InAs//In_{0.2}Ga_{0.8}As$ DWELL shows a obvious red shift comparing with that of $InAs//In_{0.15}Ga_{0.85}As$ DWELL.
Źródło:
Acta Physica Polonica A; 2012, 122, 1; 197-201
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Binding Energy of the Hydrogenic Impurity in CdTe/ZnTe Spherical Quantum Dot
Autorzy:
Stojanović, D.
Kostić, R.
Powiązania:
https://bibliotekanauki.pl/articles/1503269.pdf
Data publikacji:
2011-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
71.55.-i
Opis:
Binding energy of a hydrogenic impurity located at the center of the CdTe/ZnTe spherical quantum dot has been calculated under the effective mass approximation by solving Schrödinger equation analytically. Eigen energies are expressed in terms of the Whittaker function and Coulomb wave function. The results show that impurity binding energy strongly depends on QD size if it is around one effective Bohr radius.
Źródło:
Acta Physica Polonica A; 2011, 120, 2; 234-237
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Si Multidot FETs for Single-Electron Transfer and Single-Photon Detection
Autorzy:
Tabe, M.
Nuryadi, R.
Moraru, D.
Burhanudin, Z.
Yokoi, K.
Ikeda, H.
Powiązania:
https://bibliotekanauki.pl/articles/1813190.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
73.23.Hk
Opis:
Recently, there have been increasing demands for controlling individual electrons, photons, and dopants in developing nm scale Si devices. Our most recent results on Si single-electron nano-devices will be presented. We have demonstrated single-electron transfer in random-tunnel-junctions by a cycle of ac gate bias, detection of photons and detection of individual acceptor ions by Si single-hole transistor.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 811-814
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical Rate Equation Approach to Picosecond Charge State Dynamics in CdTe/ZnTe Quantum Dots
Autorzy:
Koperski, M.
Kazimierczuk, T.
Goryca, M.
Wojnar, P.
Golnik, A.
Kossacki, P.
Gaj, J.
Powiązania:
https://bibliotekanauki.pl/articles/1791339.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Et
73.21.La
Opis:
The rate equation is used for description of photoluminescence dynamics after pulsed excitation of various states of quantum dots. The picosecond dynamics of averaged charge state of quantum dot is described. We compare our simulations with the experiment and come up with the conclusion that probability of carrier capture weakly depends on quantum dot charge state and that electrons and holes are captured non-synchronously.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 893-895
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron and Hole States in Closed Spherical Quantum Dot with Linearly Graded Composition
Autorzy:
Kostić, R.
Stojanović, D.
Powiązania:
https://bibliotekanauki.pl/articles/1808044.pdf
Data publikacji:
2009-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.Dj
73.21.La
Opis:
The theoretical investigation of the electron and hole spectra in a quantum dot with a linearly graded composition within the effective mass approximation is presented. The particular example is β-HgS surrounded by CdS. β-HgS core of radius $r_C$ is surrounded by concentric spherical layers each of $Hg_{1-x}Cd_{x}S$ composition (x is function of r) and finally, form radius $r_S$ by CdS. The existence of these intermediate layers, as model of graded composition, influences rapidly electron and hole spectra.
Źródło:
Acta Physica Polonica A; 2009, 115, 4; 768-770
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Weldability of CuZn30 Brass/DP600 Steel Couple by Friction Stir Spot Welding
Autorzy:
Barlas, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1031898.pdf
Data publikacji:
2017-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Vj
87.15.La
Opis:
This study deals with the weldability and assessment of the friction stir spot welding of dissimilar CuZn30 brass/DP600 steel couple. The effects of axial tool load and tool hold time were evaluated in the joining experiments. The tool load forces of 3.2-4.8 kN and the tool hold times of 8 s and 12 s were applied to brass/steel bimetal sheets. Tensile-shear test was employed to investigate the mechanical properties of the joint. Optical and scanning electron microscopies were utilized to characterize the microstructure of the joint having the better mechanical performance, as well as the microhardness test. Temperature measurements were also performed between the lapped sheet faces. The results show that the vertical tool load value has reached more significant influence than the tool hold time. Furthermore, the tensile-shear failure load has increased with increasing tool load and hold time and has reached the highest value of 4.6 kN. The EDS analyses on the fractured surface depict that the copper and zinc concentrations are similar to those of CuZn30 base metal. A peak temperature of 607°C was measured in the weld centre of this joint. No significant microstructural change was observed in the steel sheet, while the fine grains with onion rings were revealed in the brass. Different hardness values were measured depending on microstructural change in the weld zone. Although the onion rings made a contribution to the microhardness, a softened stir zone (129.8 HV), with regard to the brass base metal (149.1 HV), was observed.
Źródło:
Acta Physica Polonica A; 2017, 132, 3; 991-993
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The calculation for strain distributions and electronic structure of InAs/GaAs quantum dots based on the eight-band k·p theory
Autorzy:
Shu, Changgan
Liu, Yumin
Powiązania:
https://bibliotekanauki.pl/articles/1070532.pdf
Data publikacji:
2016-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
73.63.Kv
Opis:
In order to analyze the strain distribution of InAs/GaAs quantum dot in a pyramidal geometry, the traditional calculation method is based on the single band envelope approximation with the modified band edge from the eight band k·p theory. In this paper, we use the eight band k·p Hamiltonian to calculate, and the piezoelectric effects and the electronic structure are also discussed subsequently. To this end, some necessarily derived formulae in calculations about using the finite element calculation software COMSOL are presented in this paper. The results show the details about strain distributions, piezoelectric effects and electronic structure of an InAs/GaAs pyramidal quantum dot, verify the feasibility and efficiency of the calculation method.
Źródło:
Acta Physica Polonica A; 2016, 129, 3; 371-377
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Logic operations of charge qubit in a triple quantum dot
Autorzy:
Ptaszyński, K.
Bułka, B.
Powiązania:
https://bibliotekanauki.pl/articles/1157205.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
03.67.Lx
Opis:
Studies for a single charge qubit and two capacitively coupled qubits built on triple quantum dots are presented. We show feasibility of implementing two-qubit gate operations, e.g. the CPHASE gate can be implemented with the fidelity higher than 99% for strong couplings.
Źródło:
Acta Physica Polonica A; 2016, 129, 1a; A-30-A-32
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Optical Excitonic Aharonov-Bohm Effect in a Few Nanometer Wide Type-I Nanorings
Autorzy:
Tadić, M.
Arsoski, V.
Čukarić, N.
Peeters, F.
Powiązania:
https://bibliotekanauki.pl/articles/1537808.pdf
Data publikacji:
2010-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
Opis:
The optical excitonic Aharonov-Bohm effect in type-I three-dimensional (In,Ga)As/GaAs nanorings is theoretically explored. The single-particle states of the electron and the hole are extracted from the effective mass theory in the presence of inhomogeneous strain, and an exact numerical diagonalization approach is used to compute the exciton states and the oscillator strength $f_{x}$ for exciton recombination. We studied both the large lithographically-defined and small self-assembled rings. Only in smaller self-assembled nanorings we found optical excitonic Aharonov-Bohm effect. Those oscillations are established by anticrossings between the optically active exciton states with zero orbital momentum. In lithographically defined rings, whose average radius is 33 nm, $f_{x}$ shows no oscillations, whereas in the smaller self-assembled nanoring with average radius of 11.5 nm oscillations in $f_{x}$ for the ground exciton state are found as function of the magnetic field that is superposed on a linear dependence. These oscillations are smeared out at finite temperature, thus photoluminescence intensity exhibits step-like variation with magnetic field even at temperature as small as 4.2 K.
Źródło:
Acta Physica Polonica A; 2010, 117, 6; 974-977
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Interband Optical Properties of Concentric Type-I Nanorings in a Normal Magnetic Field
Autorzy:
Arsoski, V.
Tadić, M.
Peeters, F.
Powiązania:
https://bibliotekanauki.pl/articles/1537829.pdf
Data publikacji:
2010-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
Opis:
Two concentric two-dimensional GaAs/(Al,Ga)As nanorings in a normal magnetic field are theoretically studied. The single-band effective mass approximation is adopted for both the electron and the hole states, and the analytical solutions are given. We find that the electronic single particle states are arranged in pairs, which exhibit anticrossings and the orbital momentum transitions in the energy spectrum when magnetic field increases. Their period is essentially determined by the radius of the outer ring. The oscillator strength for interband transitions is strongly reduced close to each anticrossing. We show that an optical excitonic Aharonov-Bohm effect may occur in concentric nanorings.
Źródło:
Acta Physica Polonica A; 2010, 117, 5; 733-737
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 114

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