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1
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A DFT Study of the Strain Effect on the Optical Properties of Linear and Dimerized Titanium Nanochains

100%
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.
2
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Intersubband Absorption in Quantum Dash Nanostructures

100%
Crnjanski J., Gvozdić D.
Acta Physica Polonica A
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2009
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vol. 116
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issue 4
668-671
EN
The band structure and corresponding intersubband absorption coefficient of quantum dash structures are modeled using a self-consistent single-band effective-mass approach and dipole approximation. Size fluctuation of the quantum dash ensemble, described with Gaussian distribution, is included in the model and its effects on the absorption spectrum are analyzed. The profile of the absorption spectrum is suitable for fitting with a sum of Gaussian functions. We find that the quantum dash ensemble has a pronounced and broad absorption spectrum in mid-infrared region, which becomes broader and more asymmetric with increase of the size fluctuation. In addition, for very large size fluctuation, the spectrum becomes flattened in relatively wide wavelength range.
3
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Identification of Optical Transitions from CdTe and CdMnTe Quantum Dots Embedded in ZnTe Nanowires

100%
Szymura M., Kłopotowski Ł., Wojnar P., Karczewski G., Wojtowicz T., Kossut J.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
824-826
EN
We study photoluminescence properties of CdTe and CdMnTe quantum dots embedded in ZnTe nanowires. The nanowires were grown by molecular beam epitaxy, applying the vapor-liquid-solid growth mechanism. Linear polarization anisotropy measurements allow us to assess that the excitonic transitions originate from a single nanowire. We identify the optical transitions by comparing observed spectroscopic shifts with the universal emission pattern from the epitaxial CdTe dots. We support this identification by analyzing the photoluminescence intensity dependence on excitation power.
4
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Lateral Coupling within the Ensemble of InAs/InGaAlAs/InP Quantum Dashes

100%
Ryczko K., Sęk G., Misiewicz J.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
805-808
EN
In this work we investigate the electronic structure of coupled quantum dashes. The respective confined state energy levels are calculated for various cross-sectional shapes and sizes of the dashes and in function of the lateral distance between them. The results are confronted with the existing experimental data on the optical transitions in such structures. It has been concluded that for realistic system parameters (geometry and spatial in-plane separation) the obtained direct coupling is weak and in most of the applications the dashes can be considered individually, as long as the ensemble is strongly inhomegeneous.
5
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Temperature Dependences of Optical Energy Gaps of SbSI@CNT and SbSeI@CNT

100%
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.
6
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Fluorescence Microscopy of Corrole-Single Silver Nanowire Hybrid Nanostructures

88%
Czechowski N., Olejnik M., Nowak-Król A., Piątkowski D., Heiss W., Gryko D., Mackowski S.
Acta Physica Polonica A
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2012
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vol. 122
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issue 2
333-336
EN
We report on confocal microscopy imaging of hybrid nanostructures composed of silver nanowires and corroles. Both nanomaterials were separated by a 30 nm thick SiO_2 spacer in order to inhibit fluorescence quenching. The results show that for such a hybrid nanostructure the average enhancement of the fluorescence intensity reached 2.5. Importantly, the coupling to plasmon excitations in metallic nanowires leaves no effect on the fluorescence spectrum of the organic molecules.
7
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Second Harmonic Generation in AlGaAs Nanowaveguides

88%
Rutkowska K., Duchesne D., Volatier M., Arès R., Aimez V., Morandotti R.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
725-731
EN
In this paper, we investigate semiconductor nanowaveguides (i.e. ridge waveguides with core-widths narrower than 1 μm) intended to act as novel optical light sources through nonlinear wavelength/frequency conversion. In particular, numerical calculations have been performed in order to design suitable photonic devices (fabricated in the AlGaAs/GaAs platform) capable of high efficiency second harmonic generation. Particular interest has been dedicated to the effective conversion of optical signals from 1520-1600 nm (the third telecom window) down to 760-800 nm. We demonstrate that the output wavelength (resulting from modal phase-matching) can be dynamically tuned by proper adjustment of the temperature and/or geometrical parameters of the waveguides. In addition, by changing the waveguide width it is also possible to modify the device dispersion characteristics, giving the possibility to work in the region of anomalous dispersion and thus allowing for the generation of temporal solitons.
8
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Influence of Iron Nanowires Oxidation on Their Semiconducting Properties

75%
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.
9
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TEM Study of the Structural Properties of Nanowires Based on Cd, Zn, Te grown by MBE on Silicon Substrates

51%
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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