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1
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Samarium-Doped Ceria Nanostructured Thin Films Grown on FTO Glass by Electrodepostion

100%
Živković L., Lair V., Lupan O., Cassir M., Ringuedé A.
Acta Physica Polonica A
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2011
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vol. 120
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issue 2
298-302
EN
Electrical, optical or catalytic properties of ceria can be tuned via doping by rare earth elements. The innate properties of ceria-based materials can be further amplified by using nanostructured ceria. In this study, Sm-doped ceria (SDC) coatings were grown on the FTO glass substrate by means of cathodic deposition. Films were obtained from mixed Sm^{3+}/Ce^{3+} aqueous nitrate solutions, applying -0.8V/(SCE) potential for 1 h. Selected conditions gave rise to adherent, homogeneous and well-covering nanostructured SDC thin films. EDX analysis showed that 0.8 and 1.5 mol% Sm^{3+} led to 3.4 and 6.3 at.% Sm in the SDC films. XRD and Raman analysis confirmed the formation of cubic fluorite-type CeO_{2}. However, Sm-doping decreased the crystallite size of nanostructured ceria. The effect of annealing on SDC film was also studied. An improvement in crystallite quality was found with increasing temperature. Optical absorption properties were studied and the band gap value (E_g) of 3.07 eV was determined for pure ceria. Sm-doped ceria exhibited a red shifting. The E_g values were 2.97 and 2.81 eV, in due order.
2
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Observation and Control of Interfacial Defects in ZnO/ZnSe Coaxial Nanowires

100%
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.
3
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Electron Diffraction Tomography and Dynamical Refinement for Crystal-Structure Characterization of Nanocrystalline Materials

100%
Corrêa C., Klementová M., Palatinus L.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
651-653
EN
Three-dimensional electron diffraction tomography allows one to obtain structure information from nanocrystals. However, in order to get accurate results the dynamical theory must be used due to the strong dynamical interaction between electrons and matter. Full structure refinement using dynamical theory has been in use for some time, in spite of being hampered by the fact that the intensities are very sensitive to variations of thickness and of the orientation of the sample. A remedy to this problem is the technique called precession electron diffraction. The use of precession electron diffraction in combination with electron diffraction tomography results in more accurate structure parameters and lower figures of merit in the structure refinement. The principles of electron diffraction tomography, precession electron diffraction and dynamical refinement will be demonstrated on the structural analysis of a nanowire of Ni₃Si₂.
4
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Structural and Optical Properties of ZnO Nanowires Doped with Magnesium

100%
Zhuang H., Wang J., Liu H., Li J., Xu P.
Acta Physica Polonica A
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2011
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vol. 119
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issue 6
819-823
EN
ZnO nanowires doped with Mg have been successfully prepared on Au-coated Si (111) substrates using chemical vapor deposition method with a mixture of ZnO, Mg, and activated carbon powders as reactants at 850°C. The structural, compositional, morphological and optical properties of the samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectroscopy. The nanowires are single crystalline in nature and preferentially grow up along [0001] direction with the average diameter and length of about 60 nm and several hundred micrometers, respectively, thinner and longer than the results of literature using the similar method. Room temperature photoluminescence spectroscopy shows a blueshift from the bulk band gap emission, which can be attributed to Mg doping that were detected by energy dispersive X-ray analysis EDX in the nanowires. Finally, the possible growth mechanism of crystalline ZnO nanowires is discussed briefly.
5
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Structural and Optical Characterization of GaN/AlGaN Single Quantum Disk Nanorods

100%
Almokhtar M., Emura S., Tambo H., Hasegawa S., Asahi H.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
473-475
EN
GaN/AlGaN single quantum disks on GaN nanorods were grown on Si (001) substrate with native SiO_2 layer by a plasma-assisted molecular-beam epitaxy under nitrogen-rich conditions. The transmission electron microscopy observations show single GaN nanorods images with an average thickness of 4 nm for the GaN single quantum disk and nanorod diameter of 15 nm. The observed photoluminescence spectra at 8 K show a peak at 3.475 eV, attributed to an exciton recombination in GaN. A strong peak was observed at 3.542 eV. This peak is attributed to the quantum confinement of excitons in the GaN quantum disks.
6
Content available remote

Diffraction from WS_2 and MoS_2 Nanotubes

100%
Damnjanović M., Vuković T., Milošević I.
Acta Physica Polonica A
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2011
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vol. 120
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issue 2
224-226
EN
We present a symmetry based analysis of diffraction intensities of transition metal dichalcogenide nanotubes. Obtained results point out specific features of the intensity distribution that are related to group parameters. It is possible to read out all the group parameters from diffraction patterns, and therefore to characterize nanotube, since symmetry group uniquely determines the chiralty indices.
7
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Electrochemically Deposited Cobalt Nanoarrays in SiO_2/n-Si Templates Produced by Swift Heavy Ion-Induced Modification Technology

100%
Koltunowicz T., Zhukowski P., Fedotova J., Bayev V., Streltsov E., Baran L.
Acta Physica Polonica A
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2013
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vol. 123
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issue 5
929-931
EN
Nanoarrays of Co nanorods were formed by means of electrochemical deposition in the nanoporous SiO_2/n-Si templates. Structure and magnetic properties at room temperatures were studied by means of atomic force and scanning electron microscopies, vibrating sample magnetometry. The presence of perpendicular magnetic anisotropy component at room temperature makes Co nanorods in the nanoporous SiO_2/n-Si templates promising for nanoelectronic devices and biomedical applications.
8
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Free-Standing Si and Ge, and Ge/Si Core-Shell Semiconductor Nanowires

100%
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.
9
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Magnetic and Structural Study of (ZnTe)/Co Core-Shell Nanowires Grown by Molecular Beam Epitaxy

100%
Misiuna P., Dłużewski P., Wojciechowski T., Lewińska S., Ślawska-Waniewska A., Wawro A., Wiater M., Wojtowicz T., Baczewski L.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
517-519
EN
Arrays of crystalline ZnTe nanowires grown by vapor-liquid-solid mechanism were covered with cobalt in a molecular beam epitaxy system. Magnetic and structural characterization of such core/shell nanowires was performed. Using scanning electron microscopy and transmission electron microscopy it was found that the mean shell thickness of cobalt was about 35% of the nominal deposition thickness. Deposited cobalt had a polycrystalline structure covering the ZnTe nanowires evenly along their length. With the increment of temperature during Co deposition the roughness of the nanowire sidewalls increases. Vibrating sample magnetometry measurements revealed that the magnetization easy-axis direction is perpendicular to the long axis of the nanowires, which is in agreement with theoretical predictions. Oxidation of Co shell does not change the anisotropy direction of such structures, however it increases their coercivity. Exchange bias effect at the interface of cobalt and cobalt oxides suggested by some authors is not responsible for such anisotropy orientation.
10
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Properties of GaN Nanocolumns Grown by Plasma - Assisted MBE on Si (111) Substrates

100%
Zytkiewicz Z., Dluzewski P., Borysiuk J., Sobanska M., Klosek K., Witkowski B., Setkiewicz M., Pustelny T.
Acta Physica Polonica A
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2011
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vol. 120
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issue 6A
A-15-A-16
EN
We report on growth of GaN nanocolumns by plasma assisted MBE on (111) silicon substrates and on their characterization. The nanocolumns nucleate on the substrate spontaneously without use of any catalyst, probably by the Volmer-Weber mechanism. Transmission electron microscopy analysis shows high crystalline quality of GaN nanocolumns and their good alignment with the c-axis being perpendicular to the substrate. Preliminary results on use of GaN nanocolumns in gas sensor devices are presented.
11
Content available remote

Anisotropic Magnetoresistance of Ni Nanorod Arrays in Porous SiO₂/Si Templates Manufactured by Swift Heavy Ion-Induced Modification

100%
Fedotova J., Ivanou D., Mazanik A., Svito I., Streltsov E., Saad A., Zukowski P., Fedotov A., Bury P., Apel P.
Acta Physica Polonica A
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2015
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vol. 128
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issue 5
894-896
EN
In this work anisotropic magnetoresistance in nanogranular Ni films and Ni nanorods on Si(100) wafer substrates was studied in wide ranges of temperature and magnetic field. To produce Ni films and nanorods we used electrochemical deposition of Ni clusters either directly on the Si substrate or into pores in SiO₂ layer on the Si substrate. To produce mesopores in SiO₂ layer, SiO₂/Si template was irradiated by a scanned beam of swift heavy 350 MeV ¹⁹⁷Au²⁶⁺ ions with a fluence of 5×10⁸ cm¯² and then chemically etched in diluted hydrofluoric acid. Pores, randomly distributed in the template have diameters of 100-250 nm and heights about 400-500 nm. Comparison of temperature dependences of resistance and magnetoresistance in Ni films and n-Si/SiO₂/Ni structures with Ni nanorods showed that they are strongly dependent on orientation of magnetic field and current vectors relative to each other and the plane of Si substrate. Moreover, magnetoresistance values in n-Si/SiO₂/Ni nanostructures can be controlled not only by electric field applied along Si substrate but also by additionally applied transversal bias voltage.
12
Content available remote

[100] Loading of Fcc Based Nanofibre Reinforced Composites

88%
Černý M., Pokluda J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
505-508
EN
Ab initio calculations of theoretical tensile and compressive strengths in the 〈100〉 direction of a composite having continuous nanofibre reinforcements are performed using pseudopotential approach within density functional theory. Results for iridium or platinum nanofibres in copper or gold matrices, presented as case studies, reveal that the theoretical tensile and compressive strengths almost linearly increase with increasing atomic concentration of the reinforcement exhibiting only slight positive strength deviations from the linearity for Pt-Au and slight negative deviations of the tensile strength for Ir-Cu.
13
Content available remote

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.
14
Content available remote

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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