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    Wyświetlanie 1-68 z 68
    Tytuł:
    Simulating the Electron Transmission with Different Defective Carbon Nanotubes
    Autorzy:
    Nizam, R.
    Rizvi, S.
    Azam, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1419854.pdf
    Data publikacji:
    2012-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    Opis:
    2. The transmissions of forty-eight carbon nanotube geometries to form twenty-four intramolecular junctions between every two carbon nanotubes and two simple carbon nanotubes are also taken for investigating numerically. These forty-eight carbon nanotubes form three different kinds of intramolecular junctions, which mean that each sixteen carbon nanotubes are identical to either sixteen carbon nanotubes in all respect, except three different intramolecular junctions in between them. The three intramolecular junctions, named as circumferential defective carbon nanotubes, grouped defective carbon nanotubes and distributed defective carbon nanotubes. The nature of electronic states at the interfaces and in the semiconductor section is analyzed with the help of tight-binding method. These quantum transmissions have been compared among the different defective carbon nanotubes and have been correlated with the pentagon and heptagon that formed in the intramolecular junction. It has been simulated that each pair of semiconductor-semiconductor carbon nanotubes, semiconductor-metallic carbon nanotubes and metallic-metallic carbon nanotubes transmission affect on the presence of junctions pentagons-heptagons. The least deviations transmission is observed in the circumferential defective carbon nanotubes rather than in other two and the maximum deviations are seen in the grouped defective carbon nanotubes irrespective of the joining of the carbon nanotube interface.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 1; 190-196
    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:
    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:
    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:
    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:
    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:
    Hole Subband Mixing and Polarization of Luminescence from Quantum Dashes: A Simple Model
    Autorzy:
    Kaczmarkiewicz, P.
    Musiał, A.
    Sęk, G.
    Podemski, P.
    Machnikowski, P.
    Misiewicz, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2048063.pdf
    Data publikacji:
    2011-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.67.Hc
    73.22.-f
    Opis:
    In this paper, we address the problem of luminescence polarization in the case of nanostructures characterized by an in-plane shape asymmetry. We develop a simple semi-qualitative model revealing the mechanism that accounts for the selective polarization properties of such structures. It shows that they are not a straightforward consequence of the geometry but are related to it via valence subband mixing. Our model allows us to predict the degree of polarization dependence on the in-plane dimensions of investigated structures assuming a predominantly heavy hole character of the valence band states, simplifying the shape of confining potential and neglecting the influence of the out-of-plane dimension. The energy dependence modeling reveals the importance of different excited states in subsequent spectral ranges leading to non-monotonic character of the degree of polarization. The modeling results show good agreement with the experimental data for an ensemble of InAs/InP quantum dashes for a set of realistic parameters with the heavy-light hole states separation being the only adjustable one. All characteristic features are reproduced in the framework of the proposed model and their origin can be well explained and understood. We also make some further predictions about the influence of both the internal characteristics of the nanostructures (e.g. height) and the external conditions (excitation power, temperature) on the overall degree of polarization.
    Źródło:
    Acta Physica Polonica A; 2011, 119, 5; 633-636
    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:
    Influence of Valence Band Modifications on Hydrogen Absorption in Zr-Pd Alloy Thin Films
    Autorzy:
    Jabłoński, B.
    Pacanowski, S.
    Werwiński, M.
    Marczyńska, A.
    Dawczak-Dębicki, H.
    Szajek, A.
    Smardz, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1030742.pdf
    Data publikacji:
    2018-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    82.80.Pv
    Opis:
    We study the valence band modifications of in-situ prepared nano- and polycrystalline Pd-Zr alloy thin films using X-ray photoelectron spectroscopy. Results were compared with valence bands calculated by ab initio methods. Furthermore, hydrogen absorption and desorption kinetics under pressure of about 570 mbar were studied in Pd covered nanocrystalline ZrPd₂ alloy thin film. Results showed that modifications of the valence band of the nanocrystalline alloy thin film could significantly influence on hydrogen absorption and desorption process.
    Źródło:
    Acta Physica Polonica A; 2018, 133, 3; 620-623
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    XPS Valence Band Studies of $LaNi_{5-x}Mₓ$ (M = Al, Co; x = 0, 1) Alloy Thin Films
    Autorzy:
    Skoryna, J.
    Marczyńska, A.
    Pacanowski, S.
    Szajek, A.
    Smardz, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1386422.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    71.20.-b
    Opis:
    $LaNi_{5-x}Mₓ$ (M = Al, Co) alloy thin films were prepared onto oxidised Si(100) substrates in the temperature range of 285-700 K using UHV magnetron co-sputtering. The surface chemical composition and valence bands of all the alloy thin films were measured in situ, immediately after deposition, transferring the samples to an UHV analysis chamber equipped with X-ray photoelectron spectroscopy. Results showed that the shape of the valence bands measured for the polycrystalline samples is practically the same compared to those obtained theoretically from ab initio band structure calculations. On the other hand, the X-ray photoelectron spectroscopy valence bands of the nanocrystalline thin films (especially LaNi₄Co) are considerably broader compared to those measured for the polycrystalline samples. This is probably due to a strong deformation of the nanocrystals. Therefore, the different microstructure observed in polycrystalline and nanocrystalline alloy thin films leads to significant modifications of their electronic structure.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 430-432
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electronic Properties of In Situ Prepared Nanocrystalline Fe-Ni-Ti Alloy Thin Films
    Autorzy:
    Pacanowski, S.
    Skoryna, J.
    Marczyńska, A.
    Skoryna, D.
    Smardz, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1386482.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    68.55.-a
    Opis:
    In this contribution we study experimentally the electronic properties of nanocrystalline Fe-Ni-Ti alloy thin films using X-ray photoelectron spectroscopy. The structure of the samples has been studied by X-ray diffraction. Their bulk chemical compositions were measured using X-ray fluorescence method. The surface chemical composition and the cleanness of all samples were checked in situ, immediately after deposition, transferring the samples to an UHV analysis chamber equipped with X-ray photoelectron spectroscopy. X-ray diffraction studies revealed the formation of nanocrystalline Fe-Ni-Ti alloy thin films at a substrate temperature of about 293 K. In situ X-ray photoelectron spectroscopy studies showed that the valence bands of nanocrystalline samples are broader compared to those measured for the polycrystalline bulk alloys. Such modifications of the valence bands of the nanocrystalline alloy thin films could influence on their hydrogenation properties.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 436-438
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electronic Shells of Dirac Fermions in Graphene Quantum Rings in a Magnetic Field
    Autorzy:
    Potasz, P.
    Güçlü, A.
    Hawrylak, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1791290.pdf
    Data publikacji:
    2009-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    81.07.Ta
    Opis:
    We present results of tight binding calculations demonstrating existence of degenerate electronic shells of Dirac fermions in narrow, charge neutral graphene quantum rings. We predict removal of degeneracy with finite magnetic field. We show, using a combination of tight binding and configuration interaction methods, that by filling a graphene ring with additional electrons this carbon based structure with half-filled shell acquires a finite magnetic moment.
    Źródło:
    Acta Physica Polonica A; 2009, 116, 5; 832-834
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zero-Bias Anomaly in Magnetic Tunnel Junctions
    Autorzy:
    Yang, H.
    Yang, S.
    Ilnicki, G.
    Martinek, J.
    Parkin, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1536909.pdf
    Data publikacji:
    2010-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.21.La
    73.23.-b
    73.22.-f
    Opis:
    We present experimental results, which may indicate the possibility of the coexistence of the Kondo effect and ferromagnetism in macroscopic planar magnetic tunnel junctions with a layer of nanodots inside tunnel barriers. A conductance double peak structure was observed. Magnetic field dependence of the splitting of a conductance peak, and temperature evolution of the conductance curves are well explained from the theoretical point of view according to the predictions of the Kondo physics and cotunneling in the Anderson quantum dot coupled to ferromagnetic leads.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 2; 316-318
    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
    Tytuł:
    Spin-Dependent Transport through SU(4) Kondo Dot in the Presence of Spin-Flip Processes
    Autorzy:
    Krychowski, D.
    Lipiński, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1534863.pdf
    Data publikacji:
    2010-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    73.23.-b
    73.63.Fg
    Opis:
    The spin-resolved current of carbon nanotube quantum dot coupled to ferromagnetic electrodes and influenced by spin-flip scattering is studied in the Kondo regime by the equation of motion method.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 5; 955-956
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of the Dot-Ring Nanostructure to Control Electrical Transport in the Coulomb Blockade Regime
    Autorzy:
    Janus-Zygmunt, I.
    Kędzierska, B.
    Gorczyca-Goraj, A.
    Kurpas, M.
    Maśka, M.
    Zipper, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/1376091.pdf
    Data publikacji:
    2014-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.23.Hk
    73.21.La
    73.22.-f
    Opis:
    Transport properties of a two-dimensional nanostructure composed of a quantum dot surrounded by a quantum ring (dot-ring nanostructure), are discussed. This complex system is a highly controllable object. Conduction through dot-ring nanostructure depends crucially on the coupling strength of its states to the electrodes, which is related to the spatial distribution of the electron's wave functions in dot-ring nanostructure. This distribution can be strongly modified, e.g., by the electrical gating so that the ground and excited states move between the inner dot and the outer ring. In this paper we show that this property can be used to control single-electron DC current through dot-ring nanostructure in the Coulomb blockade regime so that it can be used as a single electron transistor.
    Źródło:
    Acta Physica Polonica A; 2014, 126, 5; 1171-1173
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Kondo Effect in Carbon Nanotube Quantum Dot in a Magnetic Field
    Autorzy:
    Krychowski, D.
    Lipiński, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1810539.pdf
    Data publikacji:
    2009-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    73.23.-b
    73.63.Fg
    Opis:
    The out-of-equilibrium electron transport of carbon nanotube semiconducting quantum dot placed in a magnetic field is studied in the Kondo regime by means of the non-equilibrium Green functions. The equation of motion method is used. For parallel magnetic field the Kondo peak splits into four peaks, following the simultaneous splitting of the orbital and spin states. For perpendicular field orientation the triple peak structure of density of states is observed with the central peak corresponding to orbital Kondo effect and the satellites reflecting the spin and spin-orbital fluctuations.
    Źródło:
    Acta Physica Polonica A; 2009, 115, 1; 293-295
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Multiband Electronic Structure of Magnetic Quantum Dots: Numerical Studies
    Autorzy:
    Rederth, D.
    Oszwałdowski, R.
    Petukhov, A.
    Pientka, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1029747.pdf
    Data publikacji:
    2018-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.21.La
    73.22.-f
    75.50.Pp
    Opis:
    Semiconductor quantum dots (QDs) doped with magnetic impurities have been a focus of continuous research for a couple of decades. A significant effort has been devoted to studies of magnetic polarons (MP) in these nanostructures. These collective states arise through exchange interaction between a carrier confined in a QD and localized spins of the magnetic impurities (typically: Mn). Our theoretical description of various MP properties in self-assembled QDs is discussed. We present a self-consistent, temperature-dependent approach to MPs formed by a valence band hole. The Luttinger-Kohn k· p Hamiltonian is used to account for the important effects of spin-orbit interaction.
    Źródło:
    Acta Physica Polonica A; 2018, 133, 3; 343-349
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electronic Structure of Elongated $In_{0.3}Ga_{0.7}As//GaAs$ Quantum Dots
    Autorzy:
    Pieczarka, M.
    Musiał, A.
    Podemski, P.
    Sęk, G.
    Misiewicz, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399091.pdf
    Data publikacji:
    2013-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.67.Hc
    73.21.La
    73.22.-f
    Opis:
    In this contribution the electronic structure of large $In_{0.3}Ga_{0.7}As//GaAs$ quantum dots is studied theoretically by means of 8 band k · p modeling. These quantum dots constitute unique physical system due to the low strain limit of the Stranski-Krastanow growth mode resulting in relatively large physical volume and elongation of the quantum dots in [1-10] direction. As a result of these critical growth conditions the electronic structure is expected to be very sensitive to the nanostructure size, shape, and composition of the quantum dot as well as the accompanying wetting layer. Another peculiarity of investigated system is the confining potential which is rather shallow and weakened in comparison to standard quantum dots. It makes them very interesting in view of both fundamental study and potential applications. To reveal physical mechanisms determining the optical properties of the investigated system, the electronic structure, mainly the number of confined states, and the wave function extension as a function of both quantum dot size and geometry have been simulated numerically and the importance of electron-hole Coulomb interactions has been evaluated.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 5; 809-812
    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:
    Structure and Energetics of Fragments of the Planar α and β Boron Sheets
    Autorzy:
    Gonzalez Szwacki, N.
    Tarkowski, T.
    Majewski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398547.pdf
    Data publikacji:
    2016-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.46.-w
    68.65.-k
    73.22.-f
    Opis:
    Large scale first principles calculations based on density functional theory and using hybrid exchange-correlation functionals have been performed in order to study the structural properties and the relative stability of fragments of the planar α and β boron sheets. Based on the considered structures, we show that, in contrast to the fragments of the α -sheet, all the fragments of the β -sheet, having more than ≈30 atoms, are fully planar regardless of their shape. We conclude that the β -sheet is the only planar boron sheet reported so far that retains planarity even if it is reduced to relatively small fragments.
    Źródło:
    Acta Physica Polonica A; 2016, 129, 1a; A-148-A-149
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Efficient Emission from InAlGaAs Single Quantum Dots with Low Lattice Misfit and AlGaAs Indirect Bandgap Barrier
    Autorzy:
    Słupiński, T.
    Korona, K.
    Papierska, J.
    Borysiuk, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398581.pdf
    Data publikacji:
    2016-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.55.Cr
    73.22.-f
    78.47.jd
    Opis:
    We report on molecular beam epitaxy growth and properties of rarely studied quaternary In_{0.4}(Al_{0.75}Ga_{0.25})_{0.6}As self-assembled quantum dots, which show strong and efficient emission of red light from single quantum dots. The increased yield is, among others, due to efficient energy transfer from indirect band-gap Al_{0.75}Ga_{0.25}As barriers. To maximize photon energy emitted from quantum dots, low In composition, x_{In} = 0.4 was applied, which also lowered the lattice misfit close to the limit of 2D/3D transition in the Stranski-Krastanov growth mode. Time-resolved micro-photoluminescence shows emission at 650-750 nm. Well-resolved single quantum dot photoluminescence lines (decay time of ≈ 1-2 ns) are observed despite a high concentration ≈ 3×10¹¹ cm¯² of quantum dots. We discuss this observation assuming newly a role of carriers or excitons diffusion/tunneling between quantum dots at high surface concentration of dots and a possible role of lattice disorder inside the dot on the exciton lifetime.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 5; 1229-1232
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electronic Band Structure of Coiled Carbon Nanotubes
    Autorzy:
    Milošević, I.
    Damnjanović, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1503008.pdf
    Data publikacji:
    2011-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.48.De
    73.22.-f
    81.07.-b
    Opis:
    More than fifteen years have passed since the first report of experimental evidence of regularly coiled carbon nanotubes, but, the structure, formation mechanism and theoretical aspects of these nanotubes still remain unresolved. We propose model of hexagonal, helically coiled single wall carbon nanotubes, determine their line group symmetry and calculate electronic band structure of the relaxed configurations by means of fully symmetry adopted density functional tight binding method implemented into the POLSym code. Electrical properties of the straight and coiled carbon nanotubes of different chiralities are compared and analyzed.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 2; 221-223
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Photoluminescence Dynamics of GaN/Si Nanowires
    Autorzy:
    Korona, K.
    Zytkiewicz, Z.
    Perkowska, P.
    Borysiuk, J.
    Binder, J.
    Sobanska, M.
    Klosek, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1403621.pdf
    Data publikacji:
    2012-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.55.Cr
    73.22.-f
    78.47.jd
    Opis:
    In this work we present analysis of carriers dynamics in samples of GaN nanowires grown on silicon. The samples exhibit bright luminescence of bulk donor-bound excitons at 3.472 eV, surface defect-bound excitons at 3.450 eV (SDX) and a broad (0.05 eV) band centered at 3.47 eV caused probably by single free exciton and bi-exciton recombination. The SDX emission has long lifetime τ = 0.6 ns at 4 K and can be observed up to 50 K. At higher temperatures luminescence is dominated by free excitons. The broad excitonic band is best visible under high excitation, and reveals fast, non-exponential dynamics. We present mathematical model assuming exciton-exciton interaction leading to the Auger processes. The model includes $n^2$ (Langevin) term and describes well the non-exponential dynamics of the excitonic band.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 6; 1001-1003
    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:
    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:
    XPS and UPS Valence Band Studies of Nanocrystalline Ni-Ti Alloy Thin Films
    Autorzy:
    Pacanowski, S.
    Skoryna, J.
    Szajek, A.
    Marczyńska, A.
    Dawczak-Dębicki, H.
    Werwiński, M.
    Majchrzycki, Ł.
    Smardz, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1030748.pdf
    Data publikacji:
    2018-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    68.55.-a
    82.80.Pv
    Opis:
    In this contribution we study valence bands of in-situ prepared nanocrystalline NiTi and Ni₃Ti alloy thin films using X-ray and ultraviolet photoelectron spectroscopy. Additionally, theoretical valence band of NiTi alloy was calculated by ab-initio methods. The structure and morphology of the samples were studied by X-ray diffraction and atomic force microscopy, respectively. Furthermore, hydrogen absorption and desorption kinetics at a pressure of about 1000 mbar were studied in Pd covered nanocrystalline NiTi alloy thin film using four-point resistivity measurements. Results showed that modifications of the valence bands of the Ni-Ti thin films due nanocrystalline structure can influence on the room temperature hydrogen absorption and desorption kinetics.
    Źródło:
    Acta Physica Polonica A; 2018, 133, 3; 613-616
    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:
    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:
    Low-Temperature DC Carrier Transport in $(Co_{0.45}Fe_{0.45}Zr_{0.10})_{x}(Al_2O_3)_{1-x}$ Nanocomposites Sputtered in Mixed Argon-Oxygen Atmosphere
    Autorzy:
    Svito, I.
    Fedotov, A.
    Saad, A.
    Koltunowicz, T.
    Zukowski, P.
    Bury, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1366313.pdf
    Data publikacji:
    2014-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    72.20.Ee
    64.60.ah
    Opis:
    This paper studies the temperature dependences (2 < T < 300 K) of the DC conductivity σ(T) for the $(Co_{0.45}Fe_{0.45}Zr_{0.10})_x(Al_2O_3)_{1-x}$ nanocomposites (30 < x < 65 at.%) sputtered in Ar + $O_2$ atmosphere. It is shown that at temperatures lower than 100-150 K dependences of DC conductance on temperature for all the studied samples are due to the Shklovski-Efros variable range hopping mechanism. It was also observed that σ(x,T) dependences can be attributed to the formation of FeCo-based oxide "shells" around metallic alloy nanoparticles due to incorporation of oxygen in the vacuum chamber during the deposition procedure.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 6; 1351-1354
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Kondo-Fano Effect in Double Quantum Dot Side Attached to a Pair of Wires
    Autorzy:
    Krychowski, D.
    Lipiński, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1386758.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.10.Fk
    73.21.-b
    73.22.-f
    73.23.-b
    Opis:
    Electron tunneling through a double quantum dot side coupled to a pair of leads is examined in finite-U slave boson mean field approach. Both the two-impurity Kondo regime at half filling and one-and three-electron Kondo effects are analyzed. Special attention is paid to the case when one of the dots is coupled to ferromagnetic lead and another to nonmagnetic. Depending on the gate voltage, the same or opposite sign of polarizations of conductance of the leads is observed.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 487-489
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structural and Electronic Properties of Functionalized Graphene
    Autorzy:
    Milowska, K.
    Birowska, M.
    Majewski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1492822.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 the present paper, we study the effects of functionalization of graphene with simple organic molecules OH, and $NH_2$, focusing on the stability and band gaps of the structures. We have performed DFT calculations for graphene supercells with various numbers of the attached molecules. We have determined adsorption energies of the functionalized graphene mono- and bilayers, the changes in the geometry, and the band structure. We observe the characteristic effects such as rehybridization of the bonds induced by fragments attached to graphene and opening of the graphene band gap by functionalization. We have also studied the dependence of the adsorption energies of the functionalized graphene on the density of the adsorbed molecules. Our calculations reveal that the -OH and $-NH_2$ groups exhibit the strong cohesion to graphene layers. Further, we determine the critical density of the OH fragments which lead to the opening of the band gap. We also show how to engineer the magnitude of the band gap by functionalizing graphene with $NH_2$ groups of various concentrations.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 5; 842-844
    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
    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:
    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:
    Structural Parameters and Electronic Structure of Monolayers of Transition Metal Dichalcogenides from Ab Initio Calculations
    Autorzy:
    Woźniak, T.
    Scharoch, P.
    Winiarski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398558.pdf
    Data publikacji:
    2016-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    31.15.A-
    31.15.aj
    61.82.Fk
    73.22.-f
    Opis:
    Structural and electronic properties of the 2H-MX₂ (M = Mo, W; X = S, Se, Te) monolayers are investigated in terms of density functional theory methods. A comparison of structural parameters, energy gaps and spin-orbit coupling driven splittings obtained with different pseudopotential methods and various parametrization of exchange-correlation functional is presented.
    Źródło:
    Acta Physica Polonica A; 2016, 129, 1a; A-56-A-58
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Magnetism in Doped Two-Dimensional Honeycomb Structures of III-V Binary Compounds
    Autorzy:
    Zberecki, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1428644.pdf
    Data publikacji:
    2012-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    75.50.Pp
    75.50.Dd
    75.70.Ak
    Opis:
    Using first-principles plane-wave calculations study of magnetic properties of doped two-dimensional honeycomb structures of III-V binary compounds have been conducted for either nonmagnetic dopants or vacancies. Calculations show that all cases where magnetic moment is non-zero, are energetically more favorable. For such cases band structure and density of states were calculated and analyzed in detail. The possible applications of these structures were also discussed.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 5-6; 1240-1241
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hopping Conductance in Nanocomposites $(Fe_{0.45}Co_{0.45}Zr_{0.10})_{x}(Al_2O_3)_{1 - x}$ Manufactured by Ion-Beam Sputtering of Complex Target in $Ar+O_2$ Ambient Gas
    Autorzy:
    Kołtunowicz, T.
    Zhukowski, P.
    Fedotova, V.
    Saad, A.
    Fedotov, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1503812.pdf
    Data publikacji:
    2011-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    79.20.Rf
    73.22.-f
    84.37.+q
    72.20.Ee
    Opis:
    We report the investigation of a real part of the admittance σ of granular nanocomposites $(Fe_{0.45}Co_{0.45}Zr_{0.10})_{x}(Al_2O_3)_{1 - x}$ with 0.30 < x < 0.70 in the dielectric (hopping) regime. An analysis of the σ(T, f, x) dependences in the as-deposited and annealed films over the temperature 77 K < T < 300 K and frequency 50 < f < $10^6$ Hz ranges displayed the predominance of an activation (hopping) conductance mechanism with dσ/ dT > 0 for the samples below the percolation threshold $x_{C}$ ≈ 0.76 ± 0.05. Based on the earlier models for hopping AC conductance, computer simulation of the frequency coefficient $α_{f}$ of hopping conductance depending on the probability of jump p, frequency f, and also on the shape of σ(f) curve was performed. The experimental and simulation results revealed a good agreement.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 1; 39-42
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Model and Properties of Fullerene-Like and Wurtzite-Like ZnO and Zn(Cd)O Clusters
    Autorzy:
    Ovsiannikova, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1409333.pdf
    Data publikacji:
    2012-12
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    78.55.Et
    81.05.Dz
    81.07.Bc
    Opis:
    The electronic structure of the ground state of fullerene-like and wurtzite-like $Zn_{n}O_{n}$ and $Zn_{n - x}Cd_{x}O_{n}$ clusters has been investigated by computer physics methods. A relative evaluation of the stability and band gap width of clusters depending on the number of atoms in the cluster and its geometry has been performed. The model of a fullerene-like $(ZnO)_{60}$ particle with a mixed $sp^3//sp^2$ type of bonds has been constructed. A $(ZnO)_{12}$ cluster of $T_{h}$ symmetry was taken as a base of the model. Within the framework of the B3LYP electron density hybrid functional method with a set of 3-21G(d) split valence basis functions, a numerical investigation of the influence of the incorporation of cadmium (33%) into the ZnO matrix on the electronic structure and the band gap width has been performed.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 6; 1062-1064
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electrical Control of Spin Relaxation Time in Complex Quantum Nanostructures
    Autorzy:
    Kurpas, M.
    Kędzierska, B.
    Janus-Zygmunt, I.
    Maśka, M.
    Zipper, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/1374330.pdf
    Data publikacji:
    2014-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.25.Rb
    73.22.-f
    75.70.Tj
    85.35.Be
    Opis:
    Spin related phenomena in quantum nanostructures have attracted recently much interest due to fast growing field of spintronics. In particular complex nanostructures are important as they provide a versatile system to manipulate spin and the electronic states. Such systems can be used as spin memory devices or scalable quantum bits. We investigate the spin relaxation for an electron in a complex structure composed of a quantum dot surrounded by a quantum ring. We shown that modifications of the confinement potential result in the substantial increase of the spin relaxation time.
    Źródło:
    Acta Physica Polonica A; 2014, 126, 4a; A-20-A-24
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optimizing the InGaAs/GaAs quantum dots for 1.3 μm emission
    Autorzy:
    Maryński, A.
    Mrowiński, P.
    Ryczko, K.
    Podemski, P.
    Gawarecki, K.
    Musiał, A.
    Misiewicz, J.
    Quandt, D.
    Strittmatter, A.
    Rodt, S.
    Reitzenstein, S.
    Sęk, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1055140.pdf
    Data publikacji:
    2017-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.30.Fs
    78.67.-n
    78.67.Hc
    73.22.-f
    Opis:
    Hereby we present comprehensive experimental and theoretical study on fundamental optical properties and electronic structure of GaAs-based quantum dots grown using metalorganic chemical vapor deposition technique. The substantial redshift of emission, to the second telecommunication window of 1.3 μm, in comparison to standard InGaAs/GaAs quantum dots is obtained via strain engineering utilizing additional capping layer of In_{0.2}Ga_{0.8}As in this context referred to as strain reducing layer. It ensures lowering of the energy of the ground state transition to more application relevant spectral range. Optical properties of the quantum dot structure has been experimentally characterized by means of photoreflectance spectroscopy and power-dependent photoluminescence revealing 3 transitions originating from hybrid states confined in an asymmetric double quantum well formed of the wetting layer and strain reducing layer, as well as higher states of the quantum dots themselves with the first excited state transition separated by 67 meV from the ground state transition. Origin of the observed transitions was confirmed in theoretical modelling using 1-band single-particle approach for the quantum well part, and excitonic quantum dot spectrum obtained within 8 band k·p formalism followed by configuration interaction calculations, respectively. Additionally, photoluminescence excitation spectroscopy measurements allowed to identify a spectral range for efficient quasi-resonant excitation of the investigated quantum dots into the 2D density of states to be in the range of 835-905 nm.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 2; 386-390
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Study of the clusterization of CdO phase in ZnCdO alloys by modeling fullerene-like Zn₄₄Cd₄O₄₈ cluster
    Autorzy:
    Ovsiannikova, L.
    Kartuzov, V.
    Shtepliuk, I.
    Lashkarev, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1159858.pdf
    Data publikacji:
    2016-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    78.55.Et
    81.05.Dz
    81.07.Bc
    Opis:
    The structural, cohesive and electronic properties of fullerene-like isolated Zn₄₄Cd₄O₄₈ cluster with consideration of CdO phase clusterization are studied in the frames of density functional theory B3LYP/3-21G(d). It is revealed that an enlargement of CdO phase content in Zn₄₄Cd₄O₄₈ cluster leads to nonlinear rapid increase in cohesive energy and cluster stability, as well as band-gap energy shrinkage.
    Źródło:
    Acta Physica Polonica A; 2016, 129, 1a; A-41-A-43
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of the Package SIESTA to Linear Models of a Molecular Chromium-Based Ring
    Autorzy:
    Ślusarski, T.
    Brzostowski, B.
    Tomecka, D.
    Kamieniarz, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1534920.pdf
    Data publikacji:
    2010-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.50.Xx
    71.15.Mb
    73.22.-f
    75.30.Et
    Opis:
    We investigate for the first time the electronic and magnetic properties of the linear models of $Cr_8F_8(Piv)_{16}$ molecular ring using the SIESTA package. In the first step the proper values of the SIESTA parameters and the optimal basis set needed for the convergence of the total energy are established. Next the estimates of the magnetic coupling J confirming the previous density functional theory calculations are presented.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 5; 967-968
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Light Induced Modification of Graphene Oxide Layers on GaN Basis
    Autorzy:
    Łopion, A.
    Stobiński, L.
    Pakuła, K.
    Bożek, R.
    Kaźmierczak, P.
    Wysmołek, A.
    Stępniewski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1185429.pdf
    Data publikacji:
    2016-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    78.55.-m
    78.30.-j
    07.05.Kf
    Opis:
    Graphene oxide suspension in various solvents was spin coated on metal organic vapor phase epitaxy grown GaN/saphire layers. Samples were characterised using the Raman spectroscopy and atomic force microscopy, before and after high temperature treatment. We found that graphene oxide was modifed by high temperature treatment, however a considerable modification was also observed as a result of impinged laser light incident due to the measurements. The Raman spectra were decomposed into two contributions showing different behaviour during the Raman scattering measurements.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 5; 1169-1171
    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:
    Properties of ZnO and Zn(Cd)O Fullerene-Like Clusters with a Shell of Diamond-Like Structure with $ \text{sp}^{2}//\text{sp}^{3}$ Bonds
    Autorzy:
    Ovsiannikova, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1399133.pdf
    Data publikacji:
    2013-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    78.55.Et
    81.05.Dz
    81.07.Bc
    Opis:
    The structural, cohesive, and electronic properties of a fullerene-like $(ZnO)_{60}$ cluster with a shell of diamond-like structure with $\text{sp}^2//\text{sp}^3$ bonds have been investigated in comparison with those of clusters differing in geometry and composed of the equal number of ZnO structural units (clusters of fullerene, onion, and coordination tetrahedron) within the framework of the electron density hybride functional method (B3LYP) with a set of 6-31G(d) split valence basis functions. The fullerene-like $(ZnO)_{60}$ cluster is used as a model in an investigation of the change in the band-gap width (the decrease in the band-gap width is ≈ 0.2 eV) in the case of the substitution of Zn atoms by Cd atoms (20% of substitution) in the ZnO matrix in ZnCdO ternary structures.
    Źródło:
    Acta Physica Polonica A; 2013, 124, 5; 862-864
    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 Features of Real Part of Admittance in the Nanocomposites $(Fe_{45}Co_{45}Zr_{10})_{x}(Al_2O_3)_{100 - x}$ Manufactured by the Ion-Beam Sputtering Technique with Ar Ions
    Autorzy:
    Kołtunowicz, T.
    Zhukowski, P.
    Fedotova, V.
    Saad, A.
    Larkin, A.
    Fedotov, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1503798.pdf
    Data publikacji:
    2011-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    79.20.Rf
    73.22.-f
    84.37.+q
    72.20.Ee
    Opis:
    The temperature and frequency dependences of the admittance real part σ (T, f) in granular $(Fe_{45}Co_{45}Zr_{10})_{x}(Al_2O_3)_{100 - x}$ nanocomposite films around the percolation threshold $x_{C}$ were investigated. The behaviour of σ (T, f) vs. the temperature and frequency over the ranges 77-300 K and 50 Hz-1 MHz, respectively, displays the predominance of an activation (hopping) conductance mechanism for the samples below the percolation threshold $x_{C}$ and of a metallic one beyond the $x_{C}$ determined as 54 ± 2 at.%. The mean hopping range d for the nanoparticles diameter D was estimated at different metallic phase content x.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 1; 35-38
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Investigation of the Cadmium Effect on Properties of ZnCdO Alloys Using $Zn_{36-x}Cd_{x}O_{36}$ Clusters
    Autorzy:
    Ovsiannikova, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1375895.pdf
    Data publikacji:
    2014-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    78.55.Et
    81.05.Dz
    81.07.Bc
    Opis:
    The structural, cohesive, and electronic properties of a fullerene-like $Zn_{n-x}Cd_{x}O_{n}$ (n=36) clusters have been investigated within the framework of the electron density hybride functional method (B3LYP) with a set of 3-21G(d) split valence basis functions. These clusters are used as a model in an investigation of the change in the band-gap width in the case of the substitution of Zn atoms by Cd atoms in the ZnO matrix in ZnCdO ternary structures. The presented investigations showed that a substitution of Zn atom to Cd (5.5, 11, 16.7, 22 and 33 at.% Cd) leads to reduction of cluster stability and monotonous decrease of energy gap (0.145, 0.259, 0.354, 0.436, 0.586 eV, accordingly).
    Źródło:
    Acta Physica Polonica A; 2014, 126, 5; 1090-1092
    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:
    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:
    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:
    Spin-Dependent Effects in Helical Molecular Systems with Rashba-Like Spin-Orbit Interaction
    Autorzy:
    Gutierrez, R.
    Cuniberti, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1384094.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    73.63.-b
    72.25.-b
    87.14.gk
    87.15.Pc
    Opis:
    Strong spin-selective effects have been recently observed in both photoemission and electrical transport experiments in biomolecular systems, opening fascinating possibilities for interfacing semiconductor and biomolecular systems to create highly efficient spintronics devices. From the theoretical and experimental point of view there are strong suggestions that molecular chirality is playing a crucial role. In this study we extend a previously formulated model (R. Gutierrez, E. Díaz, R. Naaman, G. Cuniberti, Phys. Rev. B 85, 081404 (2012)) describing the linear propagation of a charge with spin along the axis of a helical charge distribution. We explore different parameter regions and show that a strong negative spin polarization as observed in the previously mentioned experiments can be obtained with reasonable values of both the electronic coupling elements and the helical field induced spin-orbit interaction.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 185-191
    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:
    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:
    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:
    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:
    Percolation Phenomena in $Cu_{x}(SiO_{y})_{100-x}$ Nanocomposite Films Produced by Ion Beam-Sputtering
    Autorzy:
    Koltunowicz, T.
    Zukowski, P.
    Czarnacka, K.
    Svito, I.
    Fedotov, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1402230.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:
    In this paper the results of examinations of nanocomposites $Cu_{x}(SiO_{y})_{100-x}$ produced by ion beam sputtering using argon ions were presented. The examinations were performed by the use of ac devices for measuring frequency in the range 50 Hz-1 MHz and temperatures from 81 K to 273 K. The measurements were performed for the samples directly after production. Based on temperature dependences of conductivity σ , which were determined at the frequency 100 Hz, the Arrhenius graphs were prepared. From these graphs conductivity activation energies ΔE were calculated. Dependences of conductivity and activation energy of electrons on the metallic phase content x at the frequency 100 Hz were determined. Analysis of the obtained dependences shows that conductivity is a parabolic function of the metallic phase content x in nanocomposites. Changes of activation energies of nanocomposites, in which metallic phase contents are in the ranges x < 12 at.% and x > 68 at.%, demonstrate negative values - metallic type of conductivity. In the range 12 at.% < x < 68 at.% activation energies have positive values - the dielectric type of conductivity. It was established that for the metallic phase content of about 68 at.% the real percolation threshold occurs, and the conduction changes from dielectric to metallic type.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 5; 908-911
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Formation of Noncoil-Like Inductance in Nanocomposites $(Fe_{0.45}Co_{0.45}Zr_{0.10})_{x}(Al_2O_3)_{1-x}$ Manufactured by Ion-Beam Sputtering of Complex Targets in $Ar+O_2$ Atmosphere
    Autorzy:
    Zhukowski, P.
    Kołtunowicz, T.
    Węgierek, P.
    Fedotova, J.
    Fedotov, A.
    Larkin, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1503848.pdf
    Data publikacji:
    2011-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    68.55.Ln
    73.22.-f
    81.40.Ef
    84.37.+q
    72.20.Ee
    Opis:
    This paper investigates the inductive contribution to AC conductance in the granular nanocomposites $(Fe_{0.45}Co_{0.45}Zr_{0.10})_{x}(Al_2O_3)_{1-x}$. The initial nanocomposites studied were manufactured in $Ar+O_2$ atmosphere by ion-beam sputtering of the target containing $Fe_{0.45}Co_{0.45}Zr_{0.10}$ and alumina stripes and then subjected to the annealing procedure in air over the temperature range 373 K < $T_{a}$ < 873 K. These samples, before and after annealing, were studied using the temperature 77 K < $T_{p}$ < 300 K and frequency 50 Hz < f < 1 MHz dependences of a real part of the admittance σ(T, f). Analysis of the observed σ (f, $T_{p}$) dependences for x < 0.5 demonstrated that in the studied samples the equivalent circuits with the capacitive and noncoil-like inductive contributions can be accomplished. Just in this case, the capacitive properties of RLC circuit with the phase angle - 90° ≤ $\Theta_{L}$ < 0° are exhibited at low frequencies and the inductive properties with 0° ≤ $\Theta_{H}$ < 90° become apparent at high frequencies. A value of the critical frequency $f_{R}$, where $\Theta_{H}$ changes sign, depends on the metallic phase concentration x, measuring temperature $T_{p}$, and annealing temperature $T_{a}$.
    Źródło:
    Acta Physica Polonica A; 2011, 120, 1; 43-45
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optical Characterization of Laser-Synthesized Anatase $TiO_{2}$ Nanopowders by Spectroscopic Ellipsometry and Photoluminescence Measurements
    Autorzy:
    Šćepanović, M.
    Grujić-Brojčin, M.
    Mirić, M.
    Dohčević-Mitrović, Z.
    Popović, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/1795613.pdf
    Data publikacji:
    2009-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.07.Wx
    78.67.Bf
    73.22.-f
    07.60.Fs
    78.55.-m
    Opis:
    Nanosized titania $(TiO_{2})$ is synthesized by laser-induced pyrolysis using $TiCl_{4}$ as a liquid precursor. X-ray diffraction and Raman scattering confirmed anatase structure of $TiO_{2}$ nanocrystals. The dielectric function ε(ω) of $TiO_{2}$ nanopowders has been determined by spectroscopic ellipsometry in the energy range from 1.5 to 6 eV at room temperature. The features observed in ε(ω) have been fitted to analytical line shapes by using the second derivatives of experimental spectra. The energies corresponding to different interband electronic transitions have been determined. Photoluminescence measurements have been carried out in vacuum for T = 20 K and T = 300 K. Under laser irradiation with sub-band gap photon energy, anatase nanocrystals have displayed strong visible photoluminescence emission. In this broad photoluminescence band different variations of line shape and position with excitation energy and temperature are observed for nanopowders with different crystallite size, pointing out to the various electronic transitions mediated by defect levels within the band gap.
    Źródło:
    Acta Physica Polonica A; 2009, 116, 4; 603-606
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electrical Characterizations of Schottky Diodes οn ITO Modified by Aromatic SAMs
    Autorzy:
    Havare, A.
    Okur, S.
    Yagmurcukardes, N.
    Can, M.
    Aydin, H.
    Seker, M.
    Demic, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1400033.pdf
    Data publikacji:
    2013-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.20.Hb
    73.20.Mf
    73.21.-b
    73.22.-f
    73.25.+i
    73.40.Ei
    73.40.Jn
    73.40.Ns
    Opis:
    In order to understand the electronic properties of the organic Schottky diode, ITO/TPD/Al and ITO/SAM/TPD/Al organic Schottky devices were fabricated to obtain current-voltage characteristics. From the slopes and y-axis intercepts of the plots, the values of the ideality factor, barrier heights of the ITO/SAM/TPD/Al diode were determined as 2.03 and 0.56 eV, respectively. The surface characterizations of modified and unmodified ITO were performed via atomic force microscopy.
    Źródło:
    Acta Physica Polonica A; 2013, 123, 2; 456-458
    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:
    DFT Estimation of Exchange Coupling Constant of Cr₈ Molecular Ring using the Hybrid Functional B3LYP
    Autorzy:
    Wojciechowski, M.
    Brzostowski, B.
    Kamieniarz, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1386209.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.50.Xx
    71.15.Mb
    73.22.-f
    75.30.Et
    31.15.E-
    71.10.-w
    Opis:
    A study of electronic and magnetic properties of an octametallic chromium-based homonuclear molecule Cr₈F₈(CO₂-C(CH₃)₃)₁₆ is presented, using density functional theory (DFT) approach and linearized augmented plane wave (LAPW) method with Perdew, Burke and Ernzerhof (PBE) and Becke 3-term correlation (B3LYP) functionals. The exchange coupling parameters between transition metals ions are extracted, taking into account two different (ferro- and antiferromagnetic) spin configurations. The value J=3.1 meV found for the hybrid B3LYP functional improves significantly the one obtained for the PBE functional and gives an evidence for the superiority of the former in simulation of molecular nanomgnets. Moreover, the hybrid functional yields excellent spin density localisation, an enhancement of the HOMO-LUMO gaps and the value 2.81 $μ_B$ of magnetic moment at the chromium centre in good agreement with experiment.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 407-409
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mapping of the DFT Spin Configuration Energies of Cr8Cd Molecular Ring onto the Energy Structure of Falicov-Kimball Model
    Autorzy:
    Wojciechowski, M.
    Brzostowski, B.
    Lemański, R.
    Kamieniarz, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1386266.pdf
    Data publikacji:
    2015-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.50.Xx
    71.15.Mb
    73.22.-f
    75.30.Et
    31.15.E-
    71.10.-w
    Opis:
    A comprehensive study of electronic and magnetic properties of a recently synthesized nonametalic chromium-based heteronuclear molecule Cr₈CdF₉(O₂C-C(CH₃)₃)₁₈ is presented, using DFT and Falicov-Kimball (FK) model approach. The magnetic moments are calculated and the spin charge density map is discussed. The exchange coupling parameters between transition metals ions are extracted, taking into account all the nonequivalent spin configurations. It is demonstrated that the energies of the spin configurations can be reproduced by the FK model with a set of parameters consistent with that for the parent Cr8 molecule. For molecular ring considered, the ground state corresponds to the antiferromagnetic configuration and the ferromagnetic configuration yields the highest energy.
    Źródło:
    Acta Physica Polonica A; 2015, 127, 2; 410-412
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Measuring the Energy Landscape in Single Semiconductor Nanowires
    Autorzy:
    Smith, L.
    Jackson, H.
    Yarrison-Rice, J.
    Jagadish, Ch.
    Powiązania:
    https://bibliotekanauki.pl/articles/1419516.pdf
    Data publikacji:
    2012-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    73.22.-f
    73.43.Fj
    73.50.Gr
    73.50.Pz
    73.63.-b
    78.30.Fs
    78.35.+c
    78.55.-m
    78.67.-n
    Opis:
    With the ability to design and control the physical structure of nanostructures to tune their electronic properties, it is increasingly important to measure the electronic structure of single nanostructures. Here we describe a number of experimental techniques for measuring the electronic structure of single semiconductor nanowires. The advantages, disadvantages and limitations of these methods will be described.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 2; 316-320
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electron and Exciton Quasi-Stationary s-States in Open Spherical Quantum Dots
    Autorzy:
    Tkach, M.
    Seti, Ju.
    Voitsekhivska, O.
    Powiązania:
    https://bibliotekanauki.pl/articles/1419890.pdf
    Data publikacji:
    2012-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.15.Dx
    73.21.La
    73.22.Dj
    73.90.+f
    Opis:
    The theoretical calculation of spectral parameters of electron and exciton quasi-stationary s-states in open spherical quantum dot is performed within the effective mass approximation and rectangular potentials model. The conceptions of probability distribution functions (over quasi-momentum or energy) of electron location inside of quantum dot and their spectral characteristics: generalized resonance energies and widths are introduced. It is shown that the generalized resonance energies and widths, obtained within the distribution functions, satisfy the Heisenberg uncertainty principle for the barrier widths varying from zero to infinity. At the same time, the ordinary resonance energies and widths defined as complex poles of scattering S-matrix, do not satisfy it for the small barrier widths and, therefore, are correct only for the open quantum dots with rather wide potential barriers.
    Źródło:
    Acta Physica Polonica A; 2012, 122, 1; 207-211
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    IR Resonant Absorption in Molecular Nanofilms
    Autorzy:
    Pelemiš, S.
    Šetrajčić, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1795586.pdf
    Data publikacji:
    2009-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.35.Aa
    73.61.Tm
    77.22.-d
    77.55.+f
    Opis:
    The paper presents a theoretical research of changes of optical properties of various nanofilm molecular crystals which are caused by the presence of two parallel and close borders. We used combined analytical-numerical calculation to find the allowed energy states of excitons and their spatial distribution (per layers) along the axis perpendicular to surface planes. We determined permittivity for the observed models of these ultrathin dielectric films and explored the influence of boundary parameters on the occurrence of discrete (per frequencies) and selective (per layers) absorption. The conditions for occurrence of smallest number of resonant absorption lines have been found and their localization has been defined.
    Źródło:
    Acta Physica Polonica A; 2009, 116, 4; 579-584
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-68 z 68

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