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Wyszukujesz frazę "73.22.-f" wg kryterium: Temat


Tytuł:
Transport and Capacitance Spectroscopy of Quantum Dots
Autorzy:
Adamowski, J.
Bednarek, S.
Szafran, B.
Powiązania:
https://bibliotekanauki.pl/articles/2027454.pdf
Data publikacji:
2001-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
73.63.-b
Opis:
A review of recent theoretical studies on a single-electron tunneling in quantum dots is presented. This effect underlies the transport spectroscopy performed on the vertical gated quantum dots and the capacitance spectroscopy on the self-assembled quantum dots. The conditions of the single-electron tunneling are formulated in terms of electrochemical potentials of the electrons in the leads and in the quantum dot. The electrochemical potentials for the electrons confined in the quantum dots can be calculated by solving the many-electron Schrödinger equation. The results obtained by the Hartree-Fock method are presented. For the vertical gated quantum dot, the realistic confinement potential is obtained from the Poisson equation. The application of the self-consistent procedure to the solution of the Poisson-Schrödinger problem is discussed. The calculated positions of the current peaks at zero bias and boundaries of the Coulomb diamonds for non-zero bias are in good agreement with experiment. The influence of an external magnetic field on the single-electron tunneling is also discussed. The spin-orbital configurations of the electrons confined in the quantum dots change with the magnetic field, which leads to features observed in the current-voltage and capacitance-voltage characteristics.
Źródło:
Acta Physica Polonica A; 2001, 100, 2; 145-163
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Strong Photoluminescence Fluctuations in Laser-Thinned Few-Layer WS₂
Autorzy:
Bala, Ł.
Łacińska, E.
Nogajewski, K.
Molas, M.
Wysmołek, A.
Potemski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1398573.pdf
Data publikacji:
2016-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
71.35.-y
78.55.-m
78.30.-j
Opis:
We present results of μ-Raman and μ-photoluminescence study of few-layer WS₂ flakes that have been locally thinned down by a focused laser beam. The Raman spectroscopy measurements prove that the investigated flake was locally thinned down to a monolayer. Interestingly, μ-photoluminescence experiments allowed us to observe huge intensity fluctuations at the boundary of laser-thinned region. Similar effects were found at the edges of a WS₂ bilayer flake, which has not been subjected to laser-thinning. The origin of the observed time evolution of the photoluminescence response is discussed in terms of potential fluctuations resulting from light-induced changes of the charge state of defects.
Źródło:
Acta Physica Polonica A; 2016, 130, 5; 1176-1178
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Van Der Waals Density Functionals for Graphene Layers and Graphite
Autorzy:
Birowska, M.
Milowska, K.
Majewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1492823.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.E-
61.46.-w
73.20.At
73.22.-f
Opis:
In this communication, we present results of theoretical studies of various systems where Van der Waals interaction plays a considerable role. In the first-principle calculations performed in the density functional theory framework we implement novel functionals accounting for Van der Waals forces and employ to the test cases of graphite and graphene layers. It turns out that this approach provides a solution to the long standing problem of overbinding between graphene layers in bulk graphite, giving the distance between the carbon layers in excellent agreement with experiment. In graphene bilayers, Van der Waals functionals lead to energetic barriers for A-B to A-A ordering of graphene bilayers that are by a factor of two smaller than the barriers obtained with standard functionals. It may be of crucial importance, particularly, if one uses atomistic ab initio methods as a starting point for multi-scale modeling of materials and for determination of effective potentials.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 845-848
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Advantages of the DFT Augmented Symmetry Approach to Simulations of the Chromium-Based Ring Cr₈ within B3LYP Functional
Autorzy:
Brzostowski, B.
Wojciechowski, M.
Kamieniarz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1030669.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Xx
71.15.Mb
73.22.-f
75.30.Et
31.15.E
Opis:
The DFT estimates of magnetic couplings in molecular nanomagnets are computationally demanding and their values have not achieved the satisfactory accuracy in spite of a lot of effort. We concentrate here on comprehensive tests for predictions of the recently proposed augmented symmetry approach aiming at reducing the computational complexity of the DFT calculations which is particularly important for the Wien2k code. Using the B3LYP functional, we demonstrate the numerical stability of magnetic couplings, magnetic moments and the HOMO-LUMO gaps, changing the fraction of exact exchange α. We reach the significant gain in the computing time without a loss in the accuracy of the final results with respect to those obtained by the standard PBE approach. We conclude that the value α=0.25 leads to best estimation of magnetic couplings for hybrid functionals within Wien2k.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 591-593
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
DFT and Falicov-Kimball Model Approach to $Cr_{9}$ Molecular Ring
Autorzy:
Brzostowski, B.
Wojciechowski, M.
Lemański, R.
Kamieniarz, G.
Timco, G.
Tuna, F.
Winpenny, R.
Powiązania:
https://bibliotekanauki.pl/articles/1368686.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Xx
71.15.Mb
73.22.-f
75.30.Et
Opis:
Based on density functional theory (DFT) calculations, we present electronic and magnetic properties of nanometallic homo-nuclear chromium-based molecular rings $Cr_{9}F_{9}Cl_{2}(O_{2}C-C(CH_{3})_{3})_{17}$ recently synthesized. The magnetic moments are calculated, the spin density maps are discussed and the exchange interaction parameter is extracted. The complementary studies are carried out using the Falicov-Kimball model which reproduces very well the energy levels determined by different magnetic broken symmetry configurations obtained by DFT.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 270-271
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
DFT Study of Octanuclear Molecular Chromium-Based Ring Using New Pseudopotential Parameters
Autorzy:
Brzostowski, B.
Ślusarski, T.
Kamieniarz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1427181.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Xx
71.15.Mb
73.22.-f
75.30.Et
Opis:
We present a comprehensive study of magnetic properties of $Cr_8F_8(Piv)_{16}$ molecular ring (in short Cr8) using the package SIESTA with several choices of chromium pseudopotential parameters. We use generalized gradient approximation to investigate properties of Cr8 ring approximated by replacing the pivallic group by H atoms (hydrogen saturation). For different choice of chromium pseudopotential we examine the electronic and magnetic properties of Cr8 molecule. We compare highest occupied molecular orbital and the lowest unoccupied molecular orbital gaps for both spin channels, magnetic moments, and exchange interaction parameter J. The influence of pseudopotential parameters on obtained results is discussed. Finally our results are compared with other theoretical approaches and experimental data.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1115-1117
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Study of Magnetic Molecules Containing Cr₉ Chromium-Based Rings within Density Functional Theory
Autorzy:
Brzostowski, B.
Wojciechowski, M.
Kamieniarz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1032265.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Xx
71.15.Mb
73.22.-f
75.30.Et
31.15.E-
Opis:
We examine the electronic and magnetic properties of three frustrated Cr₉ molecules with a single bond defect using density functional theory method. Five non-equivalent broken-symmetry spin configurations with S=±3/2 for Cr are considered, the corresponding differences between the total energies are calculated and the exchange interaction parameters J extracted using different scenarios. We find that the couplings for all molecules are antiferrimagnetic. We also estimate the fundamental gaps and in addition, the high occupied molecular orbitals and low occupied molecular orbitals are plotted and discussed.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 961-963
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron Transmission through Graphene Bilayer Flakes
Autorzy:
Chico, L.
González, J.
Santos, H.
Pacheco, M.
Brey, L.
Powiązania:
https://bibliotekanauki.pl/articles/1419511.pdf
Data publikacji:
2012-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
73.63.-b
Opis:
We investigate the electronic transport properties of a bilayer graphene flake contacted by two monolayer nanoribbons. This finite-size bilayer flake can be built by overlapping two semi-infinite ribbons. We study and analyze the electronic behavior of this structure by means of a tight-binding method and a continuum Dirac model. We have found that the conductance oscillates markedly between zero and the maximum value of the conductance, allowing for the design of electromechanical switches.
Źródło:
Acta Physica Polonica A; 2012, 122, 2; 299-303
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Friedel Oscillations in Carbon Nanotube Quantum Dots and Superlattices
Autorzy:
Chico, L.
Santos, H.
Ayuela, A.
Pelc, M.
Jaskólski, W.
Powiązania:
https://bibliotekanauki.pl/articles/1811922.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
73.90.+f
Opis:
Interface states of all-metallic carbon nanotube quantum dots and superlattices are studied within a tight-binding model. We focus on achiral systems made by connecting armchair (n,n) and zigzag (2n,0) tubes with a full ring of n pentagon-heptagon topological defects. We show that the coupling between interface states, which arise from the topological defects, reflects the existence of the Friedel oscillations in the (n,n) tube, with an unusually large decay exponent. We expect this interaction to be important for the understanding of other physical properties, such as selective dot growth, magnetic interaction through carbon tubes or optical spectroscopy of interface states.
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1085-1091
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Raman Study on Doped Multiwalled Carbon Nanotubes
Autorzy:
Costa, S.
Borowiak-Palen, E.
Powiązania:
https://bibliotekanauki.pl/articles/1807799.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Ch
73.22.-f
81.07.De
61.72.Ww
63.20.-e
Opis:
In the present study we report resonance Raman study on multiwalled carbon nanotubes treated with HCl, $HNO_3$ and $H_2SO_4$. Acids are commonly used in purification procedures in order to remove catalyst particles from the as-produced material. However, it is known that acid treatments in multiwalled carbon nanotubes can induce a surface functionalisation and intercalation of the walls, modifying their electronic properties. Here, we present a comparative study between samples of multiwalled carbon nanotubes modified with the most common acids used in the purification of carbon materials, and the influence of the acid treatment time on their vibronic properties. The samples were analysed via the Raman spectroscopy using the laser length of 785 nm. The presented data reveal the modification of the typical multiwalled carbon nanotubes Raman bands such as: disorder band (D band), the graphite band (G band), and the two-phonon second order Raman band (G' band). The last one shows a broadening effect on its line shape and the appearance of an additional peak. All the treatments enhance the number of defects in the graphitic structure of multiwalled carbon nanotubes.
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 32-35
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Permanent Magnetism in Thiol Capped Nanoparticles Gold and ZnO
Autorzy:
Crespo, P.
García, M.
Fernández-Pinel, E.
de la Venta, J.
Merino, J.
Quesada, A.
Hernando, A.
Fernández, A.
Penadés, S.
Powiązania:
https://bibliotekanauki.pl/articles/1813862.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.75.+a
73.22.-f
75.30.Hx
Opis:
In spite of the diamagnetic behavior exhibited by bulk ZnO and Au, a ferromagnetic-like behavior is induced in nanoparticles of both systems by appropriate surface functionalization. By capping with thiol derivatized molecules, magnetic hysteresis is observed even at room temperature, whereas the magnetization has a very little temperature dependence. Capping induces an alteration of their electronic configuration that depends on the capping molecule, as evidenced by X-ray absorption spectroscopy, that strongly affects their magnetic properties.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 515-520
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlations in Hexagonal Lattice Systems - Application to Carbon Nanotubes
Autorzy:
Czajka, K.
Maśka, M. M.
Powiązania:
https://bibliotekanauki.pl/articles/2041458.pdf
Data publikacji:
2004-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
71.15.Dx
Opis:
We present exact diagonalization studies of two-dimensional electron gas on hexagonal lattice. Using Lanczös method we analyze the influence of the Coulomb correlations on the density of states and spectral functions. Choosing appropriate boundary conditions we simulate the geometry of a single wall carbon nanotube. In particular, integration over the boundary condition in one direction and summation in the other one allows us to perform cluster calculations for a tube-like system with a finite diameter and infinite length.
Źródło:
Acta Physica Polonica A; 2004, 106, 5; 703-707
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Model of Radiative Recombination in (In,Al,Ga)N/GaN Structures with Significant Potential Fluctuations
Autorzy:
Dróżdż, P.
Korona, K.
Sarzyński, M.
Czernecki, R.
Skierbiszewski, C.
Muzioł, G.
Suski, T.
Powiązania:
https://bibliotekanauki.pl/articles/1185815.pdf
Data publikacji:
2016-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Cr
73.22.-f
78.47.jd
Opis:
The potential fluctuations in III-nitride quantum wells lead to many effects like emission broadening and S-shape energy vs. temperature dependence. The best description of the energy dependence comes from calculations based on Gaussian density of states. However, in most of the published reports, changes of carrier lifetime with energy and temperature are not taken into account. Since experimental evidence shows that lifetime significantly depends on energy and temperature, here we propose a model that describes two basic parameters of luminescence: lifetime of carries and emission energy as a function of temperature in the case of quantum wells and layers that are characterized by potential fluctuations. Comparison of the measured energy and lifetime dependences on temperature in specially grown InGaN/GaN quantum wells and InAlGaN layer shows very good agreement with the proposed theoretical approach.
Źródło:
Acta Physica Polonica A; 2016, 130, 5; 1209-1212
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mechanisms of Carrier Transport in $Cu_x(SiO_2)_{1-x}$ Nanocomposites Manufactured by Ion-Beam Sputtering with Ar Ions
Autorzy:
Fedotov, A.
Mazanik, A.
Svito, I.
Saad, A.
Fedotova, V.
Czarnacka, K.
Koltunowicz, T.
Powiązania:
https://bibliotekanauki.pl/articles/1402220.pdf
Data publikacji:
2015-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
84.37.+q
72.80.Ga
73.22.-f
61.46.Df
64.60.ah
Opis:
The present paper investigates the temperature/frequency dependences of admittance Z in the granular $Cu_x(SiO_2)_{1-x}$ nanocomposite films around the percolation threshold $x_{C}$ in the temperature range of 4-300 K and frequencies of 20-10⁶ Hz. The behavior of low-frequency ReZ(T) dependences displayed the predominance of electrons hopping between the closest Cu-based nanoparticles for the samples below the percolation threshold $x_{C}$ ≈ 0.59 and nearly metallic behaviour beyond the $x_{C}$. The high-frequency curves ReZ(f) at temperatures T > 10 K for the samples with x < $x_{C}$ exhibited behavior close to ReZ(f) ≈ $f^{-s}$ with s ≈ 1.0 which is very similar to the known Mott law for electron hopping mechanism. For the samples beyond the percolation threshold (x > $x_{C}$), the frequency dependences of ReZ(f) displayed inductive-like (not capacitive) behaviour with positive values of the phase shift angles.
Źródło:
Acta Physica Polonica A; 2015, 128, 5; 883-886
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetoresistance in n-Si/$SiO_2$/Ni Nanostructures Manufactured by Swift Heavy Ion-Induced Modification Technology
Autorzy:
Fedotova, J.
Ivanou, D.
Ivanova, Y.
Fedotov, A.
Mazanik, A.
Svito, I.
Streltsov, E.
Saad, A.
Tyutyunnikov, S.
Kołtunowicz, T.
Demyanov, S.
Fedotova, V.
Powiązania:
https://bibliotekanauki.pl/articles/1504014.pdf
Data publikacji:
2011-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.55.Ln
81.05.Rm
73.22.-f
73.50.Jt
Opis:
A study of magnetotransport in the n-Si/$SiO_2$/Ni nanostructures with granular Ni nanorods in $SiO_2$ pores was performed over the temperature range 2-300 K and at the magnetic fields induction up to 8 T. The n-Si/$SiO_2$/Ni Schottky nanostructures display the enhanced magnetoresistive effect at 25 K due to the impurity avalanche mechanism.
Źródło:
Acta Physica Polonica A; 2011, 120, 1; 133-135
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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