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1
Content available remote

Magnetic Force Microscopy Study of Zn_{1-x}Co_{x}O Nanowires Grown by Rapid Thermal Evaporation

100%
Aleszkiewicz M., Fronc K., Aleszkiewicz P., Zaleszczyk W., Dziawa P., Wojciechowski T., Wojtowicz T., Karczewski G.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
865-867
EN
In this work we studied domain structure of Zn_{1-x}Co_{x}O nanowires which are single arms of tetrapode crystals. The as-grown material exhibits hysteretic behavior even at room temperature as revealed by SQUID mesurements. In order to get insight into the magnetic properties of individual tetrapodes they were dismembered into nanowires of nanometric diameters, deposited on a flat substrate and imaged by magnetic force microscopy. A magnetic interaction between the magnetic force microscopy probe and single nanowires has been detected which confirms that nanometric volume of the material possesses a magnetic moment. The magnetic force microscopy contrast is attractively independent of the tip magnetization direction which indicates that shape anisotropy of nanowires is not strong enough to prevent occurrence of tip-induced magnetic field disturbance.
2
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Desorption of Gasses Induced by Ferroelectric Transition in SbSI Nanowires

80%
Szperlich P., Nowak M., Jesionek M., Starczewska A., Mistewicz K., Szala J.
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vol. 126
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issue 5
1110-1112
EN
For the first time the thermal desorption of H_2, N_2, O_2 and CO_2 is presented for antimony sulfoiodide (SbSI) xerogel made up of large quantity nanowires. The desorption has been observed near ferroelectric phase transition established at T_{c}=293.0(2) K. The Sievert measurements have shown that the hydrogen uptake is linear function of H_2 pressure (when p < 1.1×10^5 Pa). The hydrogen storage density in SbSI gel amounted 1.24× 10^{-2} wt% (for p = 1.08×10^5 Pa at room temperature).
3
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A DFT Study of the Strain Effect on the Optical Properties of Linear and Dimerized Titanium Nanochains

80%
Sohrabikia Z., Jafari M.
Acta Physica Polonica A
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2016
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vol. 129
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issue 3
344-347
EN
Optical properties of both linear and dimerized nanochains of titanium at different atomic distances are calculated using the full potential linearized augmented plane wave plus local orbital method, and using the generalized gradient approximation. When Ti nanochains were compressed, the position of critical points such as static dielectric constants and the main peaks in optical spectra shifted with an increased or decreased energy comparative to that at equilibrium constants. Under tensile strain ε_{1max}(ω) decreases in linear and dimerized structures. The plasma frequency for both structures decreases as the bond length increases. Moreover, the peaks of the energy loss function move toward higher energies with increasing bond length for linear structure, while they do not change significantly for the dimerized structure. The absorption for both nanostructures decreases by increasing the bond lengths.
4
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Observation and Control of Interfacial Defects in ZnO/ZnSe Coaxial Nanowires

80%
Bhutto W., Wu Z., Cao Y., Wang W., Kang J.
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vol. 125
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issue 4
994-996
EN
ZnO/ZnSe coaxial nanowires with different ZnO core diameters were synthesized by using a two-step chemical vapor deposition. The scanning electron microscopy images demonstrated that the coaxial nanowires with small ZnO core diameter had the smoother surface than that with large ZnO core diameter. A coherent ZnSe layer with wurtzite structure was observed in the nanowire interface between the ZnO core and the ZnSe shell by high resolution transmission electron microscopy. This coherent layer is beneficial to reduce the defect density and improve the crystal quality by suppressing the phase transition. It was found that the coherent thickness was significantly related to the ZnO core diameter. For the nanowire with large ZnO core, a thin critical thickness of 2 - 3 nm was obtained. As a result, a layer of zinc blende ZnSe appeared outside the nanowire, and a lot of defects existed in the interface between the ZnSe layers with different phase structures. For the nanowire with small ZnO core, however, the critical thickness increased and a coherent coaxial structure was observed with the same lattice spacing in the ZnO core and the ZnSe shell. To obtain defect-free coaxial nanowire, an optimal structure was also proposed by theoretical calculation.
5
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Thermal Evolution of Magnetic Interactions in Ni Nanowires Embedded in Polycarbonate Membranes by Ferromagnetic Resonance

80%
Ghaddar A., Gieraltowski J., Gloaguen F., Żuberek R., Aleshkevych P., Kazmierczak J., Slawska-Waniewska A., Szymczak H.
Acta Physica Polonica A
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2009
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vol. 116
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issue 6
1039-1043
EN
Ni polycrystalline nanowires with diameters of 50, 80, and 100 nm were electrodeposited in cylindrical pores of track-etched polycarbonate membranes. Their magnetic properties were determined as a function of temperature using ferromagnetic resonance and magnetization measurements. At room temperature, the uniaxial anisotropy is equal to the shape anisotropy whereas an additional contribution is evidenced at low temperature. This additional contribution is attributed to magnetoelastic effects induced in the nanowires due to the different thermal expansion constants of Ni and polycarbonate. The analysis of magnetization processes in Ni nanowire arrays evidenced strong dipolar interactions inside the wires due to the domain structure. The coercive field of the nanowires was shown to be nearly a linear function of the temperature and could be accounted for temperature dependence of the uniaxial anisotropy.
6
Content available remote

GaMnAs: Layers, Wires and Dots

80%
Sadowski J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1001-1012
EN
Thin layers of GaMnAs ferromagnetic semiconductor grown by molecular beam epitaxy on GaAs(001) substrates were studied. To improve their magnetic properties the post-growth annealing procedures were applied, using the surface passivation layers of amorphous arsenic. This post-growth treatment effectively increases the ferromagnetic-to-paramagnetic phase transition in GaMnAs, and provides surface-rich MnAs layer which can be used for formation of low-dimensional structures such as superlattices. If the surface rich MnAs layer consists of MnAs dots, then it is possible to grow Mn-doped GaAs nanowires.
7
Content available remote

Free-Standing Si and Ge, and Ge/Si Core-Shell Semiconductor Nanowires

80%
Peelaers H., Partoens B., Peeters F.
Acta Physica Polonica A
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2012
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vol. 122
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issue 2
294-298
EN
The properties of free-standing silicon and germanium nanowires oriented along the [110] direction are studied using different first principles methods. We show the corrections due to quasi-particles to the band structures obtained using the local-density approximation. The formation energies of B and P doped nanowires are calculated, both in the absence and presence of dangling bond defects and we link these to experimental results. Furthermore, we report on the phonon properties of pure Si and Ge nanowires, as well as Ge/Si core-shell nanowires, and discuss the differences between them.
8
Content available remote

Temperature Dependences of Optical Energy Gaps of SbSI@CNT and SbSeI@CNT

80%
Jesionek M., Nowak M., Kępińska M., Bednarczyk I.
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EN
This paper presents for the first time temperature dependences of optical energy gaps of SbSI@CNT and SbSeI@CNT, i.e. carbon nanotubes (CNTs) filled with antimony sulfoiodide (SbSI) and antimony selenoiodide (SbSeI). The heterostructures were prepared sonochemically using CNTs and elemental Sb, S or Se and I in the presence of solvent under ultrasonic irradiation. Spectral characteristics of diffusive transmittance and reflectance of SbSI@CNT and SbSeI@CNT were measured in temperature range 274 K < T < 333 K. The determinal temperature dependence of indirect forbidden optical energy gap of SbSI@CNT has been fitted with E_{gIf} (T) = (1.92(2)-3.6(6) × 10^{-4} × T) eV. Indirect allowed optical energy gap of SbSeI@CNT has been fitted with E_{gIa} (T) = (1.817(5)-7.1(2) × 10^{-4} × T) eV.
9
Content available remote

Electrochemical Deposition of Nanowires in Porous Alumina

70%
Kalska-Szostko B., Brancewicz E., Mazalski P., Sveklo J., Olszewski W., Szymański K., Sidor A.
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
542-544
EN
Electrochemical deposition is a very efficient method for producing many types of modern materials. The method is not expensive and does not have a limit for sample size. In our work the preparation of Ni, Co and Fe nanowires is presented. The obtained nanowires had different diameter and length which were tunable by template porous material and time of deposition, respectively. The quality of the prepared wires was dependent also on deposition mode. The smallest wires of the diameter around 40 nm were prepared in porous anodic alumina oxide obtained from oxalic acid. The largest ones, around 120 nm, were produced in phosphoric acid. The length could be as large as the thickness of the oxide and reached up to about 1 μm. The morphology of wires was studied by atomic force microscopy and scanning electron microscopy. The magnetic characterization was done with usage of magnetic force microscopy and the Mössbauer spectroscopy. The wires show magnetization along their growth direction.
10
Content available remote

In Situ Electron Beam Amorphization of Sb₂Te₃ within Single Walled Carbon Nanotubes

61%
Marks S., Morawiec K., Dluzewski P., Kret S., Sloan J.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1324-1327
EN
In this study, we reveal the crystallography, crystallinity, and amorphization of low-dimensional crystals of the topological insulator and phase change material Sb₂Te₃ within both discrete and bundled single walled carbon nanotubes with a diameter range spanning 1.3-1.7 nm by a combination of electron diffraction, aberration-corrected high resolution imaging, and variable dose electron beam irradiation. We further reveal that electron diffraction indicates that the crystallinity of the host single walled carbon nanotubes is largely unaffected by this process indicating that mass loss during the observed in situ glass transition had not occurred and that the template had maintained its structural integrity. Such a transition would not be possible with any other common nanoporous template for which the pores would be enlarged due to likely sintering.
11
Content available remote

Influence of Iron Nanowires Oxidation on Their Semiconducting Properties

61%
Krajewski M., Gołasa K., Wasik D.
Acta Physica Polonica A
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2016
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vol. 129
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issue 1a
A-135-A-137
EN
The main aim of this work was to study the impact of thermal annealing on the structure of iron oxide shell covering iron nanowires in relation to their semiconducting properties. Studied nanomaterial has been produced via a simple chemical reduction in an external magnetic field and then it has been thermally-treated at 400°C, 600°C and also 800°C in a slightly oxidizing argon atmosphere. Annealed iron nanowires have been characterized by means of the Raman spectroscopy and photoluminescence in order to study the structure of iron oxide shell and its influence on semiconducting properties of the whole nanostructure. According to obtained experimental results, the composition of iron oxide shell covering the studied nanomaterial is changing with annealing temperature. The thermal treatment at 400°C leads to oxidation of iron coming from the core of nanomaterial and formation of a mixture of Fe₃O₄ and α -Fe₂O₃ on the surfaces of nanowires, while annealing at higher temperatures results in further oxidation of iron as well as the phase transformation of previously created Fe₃O₄ into the most thermodynamically stable form of iron oxide at ambient conditions - α -Fe₂O₃. This oxide has a major impact on the semiconducting properties of studied nanomaterial. Thereby, the measurements of photoluminescence enabled to estimate the bandgap of bulk and surface layer at about 1.8 eV and 2.1 eV, respectively.
12
Content available remote

TEM Study of the Structural Properties of Nanowires Based on Cd, Zn, Te grown by MBE on Silicon Substrates

41%
Kaleta A., Kret S., Sanchez A., Bilska M., Kurowska B., Szczepańska A., Płachta J., Wojnar P., Wojciechowski T.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1399-1405
EN
In this work we report on the atomic structures, elemental distribution, defects and dislocations of three types of semiconductor nanowires: ZnTe, CdTe, and complex ZnTe/(Cd,Zn)Te core/shell hetero-nanowires grown by a molecular beam epitaxy on (111) Si substrate using a vapor-liquid-solid mechanism. The structural properties and the chemical gradients were measured by transmission electron microscopy methods. The nanowires reveal mainly sphalerite structure, however wurtzite nanowires were also observed.
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