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1

Thermoelectric Properties of Doped Zigzag Silicene Nanoribbons

100%

Zberecki K., Swirkowicz R., Barnaś J.

Acta Physica Polonica A

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2015

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vol. 127

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issue 2

505-507

EN

Thermoelectric properties of silicene nanoribbons doped with magnetic impurity atoms are investigated theoretically for both antiparallel and parallel orientations of the edge magnetic moments. Spin density distribution and transport parameters have been determined by ab-initio numerical methods based on the density functional theory. Doping with magnetic atoms considerably modifies the spin density distribution, leading to a ground state with a non-zero magnetic moment. Apart from this, the spin thermopower can be considerably enhanced by the impurity atoms.

2

Transport and Thermoelectric Properties of Magnetic Organic Structures

100%

Zberecki K., Swirkowicz R.

Acta Physica Polonica A

|

2018

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vol. 133

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issue 3

532-534

EN

Using ab initio methods, we study transport and thermoelectric phenomena of magnetic organic chains functionalized with nitroxide groups. We predict very good thermoelectric performance of the structure, as the conventional and spin Seebeck coefficients are remarkably enhanced. Our results suggest that magnetic organic chains would have a great potential for applications in spintronic devices.

3

Transport and Capacitance Spectroscopy of Quantum Dots

100%

Adamowski J., Bednarek S., Szafran B.

Acta Physica Polonica A

|

2001

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vol. 100

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issue 2

145-163

EN

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.

4

Band Structure and Quantum Conductance of Metallic Carbon Nanotube Superlattices

100%

Jaskólski W., Stachów A., Chico L.

Acta Physica Polonica A

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2005

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vol. 108

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issue 4

697-704

EN

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.

5

Simulation of Spin-Dependent Electronic Transport through Resonant Tunnelling Diode with Paramagnetic Quantum Well

100%

Wójcik P., Spisak B., Wołoszyn M., Adamowski J.

Acta Physica Polonica A

|

2011

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vol. 119

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issue 5

648-650

EN

The spin-dependent electronic transport is investigated in a paramagnetic resonant tunnelling diode formed from Zn_{1 - x}Mn_{x}Se quantum well between two ZnBeSe barrier layers. The spin-dependent current-voltage characteristics have been obtained in the presence of magnetic fields by solving the quantum kinetic equation for the Wigner distribution function and the Poisson equation in the self-consistent procedure. We have obtained two distinct current peaks due to the giant Zeeman splitting of electronic levels in a qualitative agreement with experiment. We have shown that the sign of spin current polarization can be reversed by tuning the bias voltage. Moreover, we have found the bias voltage windows with a nearly constant polarization.

6

Electron Transmission through Graphene Bilayer Flakes

100%

Chico L., González J., Santos H., Pacheco M., Brey L.

Acta Physica Polonica A

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2012

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vol. 122

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issue 2

299-303

EN

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.

7

Electron Transport in Magnetic Quantum Point Contacts

80%

Pietsch T., Egle S., Espy C., Strigl F., Scheer E.

Acta Physica Polonica A

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2012

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vol. 121

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issue 2

401-409

EN

In recent years, the fabrication of novel building blocks for quantum computation- and spintronics devices gained significant attention. The ultimate goal in terms of miniaturization is the creation of single-atom functional elements. Practically, quantum point contacts are frequently used as model systems to study the fundamental electronic transport properties of such mesoscopic systems. A quantum point contact is characterised by a narrow constriction coupling two larger electron reservoirs. In the absence of a magnetic field, the conductance of these quantum point contacts is quantised in multiples of 2 e^2/h, the so-called conductance quantum (G_0). However, in the presence of magnetic fields the increased spin-degeneracy often gives rise to a deviation from the idealized behaviour and therefore leads to a change in the characteristic conductance of the quantum point contact. Herein, we illustrate the complex magnetotransport characteristics in quantum point contacts and magnetic heterojunctions. The theoretical framework and experimental concepts are discussed briefly together with the experimental results as well as potential applications.

8

Electrical Resistivity of the Monoatomic Metallic Layer

80%

Paja A., Działo A.

Acta Physica Polonica A

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2013

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vol. 123

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issue 4

770-772

EN

We present new formula which describes the change of electrical resistivity of a monoatomic metallic layer with temperature. The results are compared with those given by the Bloch-Grüneisen formula for bulk metals. Our calculated values compared with those for bulk materials are significantly higher at low temperatures (T<0.1θ) and apparently lower at the remaining range of temperatures. Both effects can be explained by the low dimensionality of the sample.

9

Threshold Effects in Three-Terminal Hybrid Systems

80%

Michałek G.

Acta Physica Polonica A

|

2014

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vol. 126

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issue 1

224-225

EN

In the paper we study transport in the three terminal hybrid devices with quantum dot. Our attention is focused on the conductance threshold effects (so called Wigner singularities) caused by the back action from the side-wire. In particular we study influence of the direct electron transfer (ET) and crossed Andreev reflection (CAR) processes on the conductance caused by the direct Andreev reflection (DAR) processes.

10

An Experimental Investigation of Electrical Conductivity of Y₃Al₅O₁₂-Ethylene Glycol Nanofluids

80%

Fal J., Witek A., Gizowska M., Cholewa M., Żyła G.

Acta Physica Polonica A

|

2017

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vol. 132

|

issue 1

149-151

EN

Paper presents results of experimental studies of electrical conductivity of yttrium aluminum garnet-ethylene glycol (Y₃Al₅O₁₂-EG, YAG-EG) nanofluids, which were prepared by dispersing commercially available nanoparticles manufactured by Baikowski (Annecy, France, ID LOT: 18513) in ethylene glycol. The electrical conductivity was measured using conductivity meter MultiLine 3410 (WTW GmBH, Weilheim, Germany). In turn the temperature was stabilized in a water bath MLL 547 (AJL Electronic, Cracow, Poland). The electrical conductivity of YAG-EG nanofluids with various mass concentrations form 5% to 20% was investigated at different ambient temperatures. The experimental data indicate that changing volume fraction of YAG nanoparticles in ethylene glycol cause change of electrical conductivity of nanofluid. It was also presented that electrical conductivity depends on temperature of materials.

11

Application of Non-Classical Distribution Function to Transport Properties of Semiconductor Nanodevices

80%

Wójcik P., Spisak B., Wołoszyn M., Adamowski J.

Acta Physica Polonica A

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2008

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vol. 114

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issue 5

1431-1436

EN

The non-classical distribution function formalism is used for studying the electron transport in a nanosystem. We calculated the current-voltage characteristics of a triple barrier one-dimensional nanostructure which is connected to three-dimensional (highly doped semiconductor) reservoirs by the ohmic contacts. We also estimated the peak-to-valley ratio for the considered nanostructure and discussed the effect of switching the bias from peak-to-valley and from valley-to-peak voltages.

12

Electrical Conductivity of Ethylene Glycol Based Nanofluids with Different Types of Thulium Oxide Nanoparticles

80%

Fal J., Sidorowicz A., Żyła G.

Acta Physica Polonica A

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2017

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vol. 132

|

issue 1

146-148

EN

The paper presents experimental investigation on electrical conductivity of thulium oxides-ethylene glycol (Tm₂O₃-EG) nanofluids based on nanoparticles with three different sizes, and prepared in different conditions. Nanofluids were prepared with two-step method with use of the nanoparticles obtained by precipitation method. Measurements were conducted at constant temperature 293.15 K for various mass concentrations from 0% to 20% with 5% step. The electrical conductivity was measured using conductivity meter MultiLine 3410 (WTW GmBH, Weilheim, Germany) and temperature was stabilized in a water bath MLL 547 (AJL Electronic, Cracow, Poland). The results indicate that increase in mass concentration of nanoparticles in base fluid causes increase in electrical conductivity of Tm₂O₃-EG nanofluids. The enhancement in electrical conductivity of nanosuspensions of thulium oxide is dependent on particle size.

13

Low-Dimensional Thermoelectricity

80%

Heremans J.

Acta Physica Polonica A

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2005

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vol. 108

|

issue 4

609-634

EN

Thermoelectric materials are used as solid-state heat pumps and as power generators. The low efficiency of devices based on conventional bulk thermoelectric materials confines their applications to niches in which their advantages in compactness and controllability outweigh that drawback. Recent developments in nanotechnologies have led to the development of thermoelectric nano-materials with double the efficiency of the best bulk materials, opening several new classes of applications for thermoelectric energy conversion technology. We review here first the physical mechanisms that result in the superior thermoelectric performance of low-dimensional solids, compared to bulk thermoelectric materials: they are a reduction of the lattice thermal conductivity, and an increase in the Seebeck coefficient S for a given carrier density. The second part of this review summarizes experimental results obtained on macroscopic arrays of bismuth, antimony, and zinc nanowires with diameters ranging from 200 to 7 nm. We show how size-quantization effects greatly increase S for a given carrier concentration, as long as the diameter of the nanowires remains above 9 nm, below which localization effects start dominating. In a third part, we give data on PbTe nanocomposites, particularly bulk samples containing 30~nm diameter Pb inclusions. These inclusions affect the electron scattering in such a way as to again increase the Seebeck coefficient.

14

Interplay of Kondo and Fano Resonance in Electronic Transport in Nanostructures

80%

Bułka B., Stefański P., Tagliacozzo A.

Acta Physica Polonica A

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2005

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vol. 108

|

issue 4

555-569

EN

Quantum interference and electronic correlations are processes relevant for electronic transport in nanostructures. We present theoretical studies of transport for various models, which take into account these processes and describe the Fano resonance as well as many-body effects like the Kondo resonance. The results are compared with transport measurements performed on a small quantum dot strongly coupled to electrodes, a large semi-open quantum dot, a side-attached quantum dot to a quantum wire systems and a quantum dot embedded in the metallic ring. We show how conductance characteristics of the Kondo and the Fano resonance are modified in different situations.

15

Molecular Electronics: A Review of Experimental Results

80%

Erbe A., Verleger S.

Acta Physica Polonica A

|

2009

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vol. 115

|

issue 2

455-461

EN

Molecular electronics aims for scaling down electronics to its ultimate limits by choosing single molecules as the building blocks of active devices. The advantages of this approach are the high reproducibility of molecular synthesis on the nanometer scale, the ability of molecules to form large structures by self-assembly, and the huge versatility of molecular complexes. On the other hand, conventional contacting techniques cannot form contacts on the single molecule scale and imaging techniques nowadays cannot provide a detailed image of such junctions. Therefore, the fabrication has to rely to some degree on self-organization of the constituents. The proof that a molecule has been contacted successfully can only be given by indirect methods, for example by measuring the current transport through the junctions. Here we give an overview of various techniques that were used successfully to contact molecules and to characterize them electrically. The techniques range from methods to contact single molecules to such which can be used to characterize ensembles of molecules. Especially, the comparison between such different techniques shows that a single measurement is always prone to artefacts originating from the unknown microscopic details of the junctions. It is therefore necessary to perform a statistically relevant number of measurements in order to resolve molecular properties. Various properties of the molecules can be studied. Special examples are the influence of conformational changes of the molecules, differences between various coupling endgroups of the molecules and effects of light-irradiation onto the molecular junctions.

16

Thermoelectric Effects in Carbon Nanotube Quantum Dot in the Kondo Regime

80%

Krychowski D., Lipiński S.

Acta Physica Polonica A

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2008

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vol. 113

|

issue 2

645-649

EN

Thermoelectric effects in a carbon nanotube quantum dot in the Kondo regime are studied by the equation of motion method. The thermopower is highly sensitive to the structure of the spectral density near the Fermi edge. For temperatures close to the Kondo temperature the thermopower approaches a local minimum, which becomes sharper for orbital energies closer to the Fermi level. For higher temperatures the tjermopower increases, but in the temperature range corresponding to charging energy it again drops and achieves significant negative values. We examine the consequences of symmetry breaking of spin-orbital SU(4) system on thermopower.

17

Quantum States of Self-Assembled InAs Dots Probed by Magneto-Tunneling Spectroscopy

80%

Patanè A., Eaves L., Main P., Levin A., Zambrano M., Henini M., Vdovin E., Dubrovskii Y., Hill G.

Acta Physica Polonica A

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2001

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vol. 100

|

issue 2

165-173

EN

We present an experimental study of the electron wave function in InAs/GaAs self-assembled quantum dots. Magneto-tunneling spectroscopy is employed as a non-invasive probe to produce two-dimensional images of the probability density of an electron confined in a quantum dot. The images reveal the elliptical symmetry of the ground state and the characteristic lobes of the higher energy states of the dots.

18

Size Effects on the Electrical Resistivity of the Ultra-Thin Metallic Film

80%

Paja A., Działo A.

Acta Physica Polonica A

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2014

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vol. 125

|

issue 5

1220-1223

EN

In this article we investigate the electron-phonon interaction in metals in the system strongly reduced in one dimension. The Fermi sphere which represents the free-electron structure of a bulk metal was replaced by a discrete set of the Fermi disks. Using the variational expression for resistivity the temperature and film thickness dependences of the resistivity were derived and compared with experimental data.

19

Electron Transport and Spin Scattering in Very Thin Disordered Metallic Films

80%

Paja A., Spisak B.

Acta Physica Polonica A

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2007

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vol. 112

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issue 6

1289-1295

EN

We consider the electron transport through a very thin disordered metallic film doped with magnetic impurities. We treat the film as a quasi-two-Łinebreak -dimensional system with structural disorder where some ions have spins and other are spinless. The interaction of conduction electrons with localized spins is described by means of the exchange term of the Hamiltonian. The scattering is treated in the first Born approximation and the potential is assumed to be the Coulomb screened one. The total effective cross-section is calculated as a sum of the part responsible for the potential scattering and the second part which comes from the spin-spin scattering. The Fermi sphere splits into separate sheets due to the finite size of the system in the z direction, therefore, the cross-section and the relaxation time are calculated for each sheet independently. The total transport relaxation time and the conductivity are obtained as functions of the thickness of the system and the contents of magnetic impurities. Some model calculations have been made for a thin disordered film of copper doped with manganese.

20

Fabrication and Magnetotransport Properties of Carbon Films with Embedded Metal Nanoclusters

80%

Ksenevich V., Bashmakov I., Melnikov A., Wieck A.

Acta Physica Polonica A

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2005

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vol. 107

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issue 2

356-360

EN

2-dimensional arrays of Co- and Pd-clusters embedded in carbon films were fabricated by means of heat-treatment method of carboxylated cellulose films after the exchange of COOH-group protons by Co- and Pd-cations. The sizes of metal clusters within range 10 nm-1μm were obtained in dependence on the heat-treatment temperature. The dependencies of the resistance on temperature and magnetic field for the samples annealed at T=700ºC and 900ºC were measured. The R(T) dependencies both for carbon films with Co- and Pd-clusters can be fitted by expression R=R_0 exp(T_0/T)^{1/n} inherent for variable-range hopping. In the whole range of investigated magnetic field and temperature magnetoresistance was negative and can be related to quantum interference in the variable range hopping transport along neighboring alternative paths.

Refine search results

Thermoelectric Properties of Doped Zigzag Silicene Nanoribbons

Transport and Thermoelectric Properties of Magnetic Organic Structures

Transport and Capacitance Spectroscopy of Quantum Dots

Band Structure and Quantum Conductance of Metallic Carbon Nanotube Superlattices

Simulation of Spin-Dependent Electronic Transport through Resonant Tunnelling Diode with Paramagnetic Quantum Well

Electron Transmission through Graphene Bilayer Flakes

Electron Transport in Magnetic Quantum Point Contacts

Electrical Resistivity of the Monoatomic Metallic Layer

Threshold Effects in Three-Terminal Hybrid Systems

An Experimental Investigation of Electrical Conductivity of Y₃Al₅O₁₂-Ethylene Glycol Nanofluids

Application of Non-Classical Distribution Function to Transport Properties of Semiconductor Nanodevices

Electrical Conductivity of Ethylene Glycol Based Nanofluids with Different Types of Thulium Oxide Nanoparticles

Low-Dimensional Thermoelectricity

Interplay of Kondo and Fano Resonance in Electronic Transport in Nanostructures

Molecular Electronics: A Review of Experimental Results

Thermoelectric Effects in Carbon Nanotube Quantum Dot in the Kondo Regime

Quantum States of Self-Assembled InAs Dots Probed by Magneto-Tunneling Spectroscopy

Size Effects on the Electrical Resistivity of the Ultra-Thin Metallic Film

Electron Transport and Spin Scattering in Very Thin Disordered Metallic Films

Fabrication and Magnetotransport Properties of Carbon Films with Embedded Metal Nanoclusters