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Wyświetlanie 1-15 z 68
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:
Collective Phenomena in Multiwall Carbon Nanotubes
Autorzy:
Margańska, M.
Szopa, M.
Zipper, E.
Powiązania:
https://bibliotekanauki.pl/articles/2038389.pdf
Data publikacji:
2004-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
73.23.Ra
Opis:
Collective phenomena due to persistent currents in carbon multiwall nanotubes are studied. The formula for persistent currents minimising free energy and conditions for the stability of persistent currents in multiwall nanotubes in magnetic field are derived. Numerical calculations performed show the possibility of obtaining spontaneous currents in two optimal configurations: undoped armchair-only multiwall nanotubes up to 0.01 K, and zig-zag-chiral-chiral-zig-zag multiwall nanotubes doped to -3.033 eV up to about 1 K. The latter configuration may exhibit also the diamagnetic expulsion of magnetic field, which according to our calculations can reach 20% of the external flux.
Źródło:
Acta Physica Polonica A; 2004, 106, 5; 609-616
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:
Metastability of Band-Gap Energy in GaInNAs Compound Investigated by Photoreflectance
Autorzy:
Kudrawiec, R.
Misiewicz, J.
Pavelescu, E.-M.
Konttinen, J.
Pessa, M.
Powiązania:
https://bibliotekanauki.pl/articles/2038258.pdf
Data publikacji:
2004-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
78.66.-w
78.30.-j
Opis:
The band-gap energy of GaInNAs layers lattice-matched to GaAs substrate and annealed under different temperatures is investigated by photoreflectance spectroscopy. Different nitrogen nearest-neighbor environments of N atom appear in GaInNAs layers due to the post-growth annealing. It leads to an energy-fine structure of the band gap, i.e. well separated photoreflectance resonances related to different nitrogen nearest-neighbor environments (N-Ga$\text{}_{4-m}$In$\text{}_{m}$ (0≤ m≤ 4) short-range-order clusters). The temperature dependence of the band gap E(T) related to different N-Ga$\text{}_{4-m}$In$\text{}_{m}$ clusters is investigated in 10-280 K temperature range, and Varshni and Bose-Einstein parameters for E(T) are determined.
Źródło:
Acta Physica Polonica A; 2004, 106, 2; 249-263
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Band Structure and Quantum Conductance of Metallic Carbon Nanotube Superlattices
Autorzy:
Jaskólski, W.
Stachów, A.
Chico, L.
Powiązania:
https://bibliotekanauki.pl/articles/2043721.pdf
Data publikacji:
2005-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
73.63.-b
Opis:
The electronic structure and quantum conductance of rotationally invariant (6,6)/(12,0) and rotationally non-invariant (5,5)/(8,2) superlattices made of metallic carbon nanotubes are investigated. It is shown that, except in the limit of very large periods, the quantum conductance of such superlattices does not critically depend on their rotational invariance, although it does in case of quantum dots and single junctions made of these nanotubes.
Źródło:
Acta Physica Polonica A; 2005, 108, 4; 697-704
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Size Effects in Radiospectroscopy Spectra of Ferroelectric Nanopowders
Autorzy:
Glinchuk, M. D.
Kondakova, I. V.
Laguta, V. V.
Slipenyuk, A. M.
Bykov, I. P.
Ragulya, A. V.
Klimenko, V. P.
Powiązania:
https://bibliotekanauki.pl/articles/2043389.pdf
Data publikacji:
2005-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
61.72.Hh
68.35.Rh
Opis:
The theoretical and experimental investigation of ferroelectric nanopowders is performed. The manifestation in radiospectroscopy spectra of size driven ferroelectric-paraelectric phase transition at some critical particle average size R = R$\text{}_{c}$ was the main goal of the consideration. In theoretical part the size effect for the materials with ferroelectric tetragonal phase at room temperature and cubic paraelectric phase was considered allowing for the spontaneous polarization inhomogeneity inside a particle and distribution of particle sizes. In ESR the transformation of the spectra from tetragonal symmetry to cubic symmetry lines with decrease in nanoparticle sizes was calculated. The method of R$\text{}_{c}$ value extraction from the ratio of the different symmetry lines intensities in the absorption spectra was proposed. Measurements of Fe$\text{}^{3+}$ ESR spectra in nanopowder of BaTiO$\text{}_{3}$ were carried out at room temperature. The samples were prepared by rate-controlled method with different particle sizes, which depend on annealing temperature. The decrease in intensity of tetragonal symmetry ESR lines of Fe$\text{}^{3+}$ and appearance of cubic symmetry line with asymmetry of the shoulders was observed with the average sizes decrease with complete disappearance of tetragonal spectrum at R ≤ 40 nm. The comparison of the theory with experiment was carried out. The theory fits experimental data pretty good. The value of critical size R$\text{}_{c}$ ≈ 40 nm was extracted from ESR data. The asymmetry and broadening of right hand side shoulder of ESR cubic symmetry line was shown to be related to contribution of paramagnetic centers in the vicinity of the particles surface with lower than cubic symmetry. The deconvolution of the cubic line allowed to show that this region size is about 3 nm.
Źródło:
Acta Physica Polonica A; 2005, 108, 1; 47-60
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Size Modification of Nanographite System of Activated Carbon Fibers Studied by EPR
Autorzy:
Kempiński, M.
Kempiński, W.
Śliwińska-Bartkowiak, M.
Powiązania:
https://bibliotekanauki.pl/articles/2043617.pdf
Data publikacji:
2005-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.81.Uv
73.20.-r
73.22.-f
76.30.-v
74.78.Na
Opis:
We report results of EPR measurements of activated carbon fibers. Experiments made for pristine activated carbon fibers and activated carbon fibers with adsorbed molecules (CCl$\text{}_{4}$, C$\text{}_{6}$H$\text{}_{5}$NO$\text{}_{2}$, and H$\text{}_{2}$O) confirmed the localized character of paramagnetic centers observed in the system. Pristine activated carbon fibers are characterized by single Lorentzian line. Broader component of EPR signal appears when guest molecules are adsorbed in nanopores. The strongest localization is observed for water-filled activated carbon fibers nanopores (with hydrophobic pore walls) where changes in distance between nanographite particles were monitored by the g-shift to higher values. This process is related to stronger spin-orbit interaction of electrons trapped at nanographite particles compressed by guest molecules.
Źródło:
Acta Physica Polonica A; 2005, 108, 2; 339-343
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quantized Absorption Strength of Multi-Exciton Quantum Dots
Autorzy:
Wójcik, K.
Grodecka, A.
Wójs, A.
Powiązania:
https://bibliotekanauki.pl/articles/2047045.pdf
Data publikacji:
2006-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
78.67.Hc
71.35.-y
Opis:
Energy and absorption/recombination spectra of up to two electron-hole pairs confined in a spherical quantum dot are studied numerically as a function of dot radius (i.e., confinement volume). The transition between fermionic and bosonic behavior of the confined excitons is identified in coincidence with enhancement of low-energy absorption strength.
Źródło:
Acta Physica Polonica A; 2006, 110, 3; 423-428
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Energy and Optical Absorption Spectra of Multiply Charged Anisotropic Quantum Boxes
Autorzy:
Trojnar, A.
Małachowski, T.
Wójs, A.
Powiązania:
https://bibliotekanauki.pl/articles/2047372.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
78.67.Hc
71.35.-y
71.35.Pq
Opis:
Using a simple model of a two-dimensional rectangular quantum box we study the effects of size and anisotropy on the energy and photoluminescence spectra of neutral and charged quantum dots. The competition of symmetries and energy/length scales of the free exciton or trion and of the confining potential is analyzed. The numerical calculations consisted of the diagonalization of the few-electron-hole Hamiltonian matrices in the full configuration-interaction basis, with the simultaneous resolution of the conserved orbital and spin quantum numbers.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 173-176
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Surface Plasmon Frequency Spectrum in a System of Two Spherical Dielectric Coated Metallic Nanoparticles
Autorzy:
Makaryan, T.
Melikyan, A.
Minassian, H.
Powiązania:
https://bibliotekanauki.pl/articles/2047874.pdf
Data publikacji:
2007-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
Opis:
Semi-analytical method of surface plasmon frequency calculation for the system of two almost touching coupled dielectric coated metallic nanospheres is presented. The method allows transforming the problem to numerical solution of two simple algebraic equations for arbitrary values of parameters - particle radius, distance between sphere centers, dielectric permittivity of the matrix, dielectrics and metals. It is especially easy to get the obvious graphical solution. The surface plasmon frequencies of longitudinal and transversal oscillations of the system are calculated and good agreement with the experimental results is achieved.
Źródło:
Acta Physica Polonica A; 2007, 112, 5; 1025-1029
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:
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:
Ab Initio Analysis of a Quantum Dot Induced by a Local External Potential in a Semiconducting Carbon Nanotube
Autorzy:
Kostyrko, T.
Krompiewski, S.
Powiązania:
https://bibliotekanauki.pl/articles/1810605.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.48.De
85.35.Kt
73.21.La
73.22.-f
Opis:
Using the density functional theory we study the influence of external charge probes on the electronic structure of semiconducting carbon nanotubes in the vicinity of the Fermi level. We show that the spatially limited potential due to the probe can create localized electronic states in the energy gap and at the edges of the conductance band. By filling these localized states with additional electrons one obtains a quantum dot, which can be tuned by modifying the properties of the external charge probe. We analyze dependence of the electronic structure of the dot on the spatial extension of the potential as well as on the nanotube radius.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 387-389
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ab Initio Study of Functionalized Carbon Nanotubes
Autorzy:
Milowska, K.
Birowska, M.
Majewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1791295.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.ae
31.15.E-
61.46.Fg
61.48.De
73.22.-f
81.07.De
Opis:
In the present paper, we study the stability of (9, 0), (10, 0), (11, 0) carbon nanotubes functionalized with simple organic molecules $-CH_{n}$ (for n = 2, 3, 4). Our studies are based on ab initio calculations within the framework of the density functional theory. We determine binding energies of the functionalized carbon nanotubes and the changes in the geometry and electronic structure caused by the functionalization. We observe the characteristic effects such as rehybridization of the bonds induced by fragments attached to carbon nanotubes and pentagon/heptagon (5/7) defects in $-CH_{2}$ functionalized carbon nanotubes. We study also dependence of the binding energies of the functionalized carbon nanotubes on the density of the adsorbed molecules and diameter of the single-wall carbon nanotubes. Our calculations reveal that the $-CH_{2}$ fragments exhibit the strongest cohesion and we determine the critical density of the $-CH_{2}$ fragments which could be adsorbed.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 841-843
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cotunneling Transport at Singlet-Triplet Transition in Carbon Nanotube Quantum Dots
Autorzy:
Ilnicki, G.
Moriyama, S.
Martinek, J.
Fuse, T.
Ishibashi, K.
Powiązania:
https://bibliotekanauki.pl/articles/1810544.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.-f
73.23.Hk
73.63.Fg
Opis:
Electronic transport through a quantum dot in the Coulomb-blockade cotunelling regime is investigated both experimentally and theoretically, where a single-wall carbon-nanotube weakly coupled to metallic leads plays a role of the dot. We observe a pronounced current peak for the singlet-triplet transition in a half-shell filling regime due to inelastic cotunneling processes. Using the second order perturbation theory we explain physical mechanisms determining the details of signal.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 299-302
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 68

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