References of "Aabdin, Zainul"
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See detailPhonon spectroscopy in a Bi2Te3 nanowire array
Bessas, Dimitrios; Toellner, William; Aabdin, Zainul et al

in Nanoscale (2013), 5(21), 10629-10635

The lattice dynamics in an array of 56 nm diameter Bi2Te3 nanowires embedded in a self-ordered amorphous alumina membrane were investigated microscopically using Te-125 nuclear inelastic scattering. The ... [more ▼]

The lattice dynamics in an array of 56 nm diameter Bi2Te3 nanowires embedded in a self-ordered amorphous alumina membrane were investigated microscopically using Te-125 nuclear inelastic scattering. The element specific density of phonon states is measured on nanowires in two perpendicular orientations and the speed of sound is extracted. Combined high energy synchrotron radiation diffraction and transmission electron microscopy was carried out on the same sample and the crystallinity was investigated. The nanowires grow almost perpendicular to the c-axis, partly with twinning. The average speed of sound in the 56 nm diameter Bi2Te3 nanowires is similar to 7% smaller with respect to bulk Bi2Te3 and a decrease in the macroscopic lattice thermal conductivity by similar to 13% due to nanostructuration and to the reduced speed of sound is predicted. [less ▲]

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See detailNanostructure, Excitations, and Thermoelectric Properties of Bi2Te3-Based Nanomaterials
Aabdin, Zainul; Peranio, N.; Eibl, O. et al

in Journal of Electronic Materials (2012), 41(6), 1792-1798

The effect of dimensionality and nanostructure on thermoelectric properties in Bi2Te3-based nanomaterials is summarized. Stoichiometric single-crystalline Bi2Te3 nanowires were prepared by potential ... [more ▼]

The effect of dimensionality and nanostructure on thermoelectric properties in Bi2Te3-based nanomaterials is summarized. Stoichiometric single-crystalline Bi2Te3 nanowires were prepared by potential-pulsed electrochemical deposition in a nanostructured Al2O3 matrix, yielding transport in the basal plane. Polycrystalline, textured Sb2Te3 and Bi2Te3 thin films were grown at room temperature using molecular beam epitaxy and subsequently annealed at 250A degrees C. Sb2Te3 films revealed low charge carrier density of 2.6 x 10(19) cm(-3), large thermopower of 130 V K-1, and large charge carrier mobility of 402 cm(2) V-1 s(-1). Bi-2(Te0.91Se0.09)(3) and (Bi0.26Sb0.74)(2)Te-3 nanostructured bulk samples were prepared from as-cast materials by ball milling and subsequent spark plasma sintering, yielding grain sizes of 50 nm and thermal diffusivities reduced by 60\%. Structure, chemical composition, as well as electronic and phononic excitations were investigated by x-ray and electron diffraction, nuclear resonance scattering, and analytical energy-filtered transmission electron microscopy. calculations yielded point defect energies, excitation spectra, and band structure. Mechanisms limiting the thermoelectric figure of merit for Bi2Te3 nanomaterials are discussed. [less ▲]

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See detailSb2Te3 and Bi2Te3 Thin Films Grown by Room-Temperature MBE
Aabdin, Zainul; Peranio, N.; Winkler, M. et al

in Journal of Electronic Materials (2012), 41(6), 1493-1497

Sb2Te3 and Bi2Te3 thin films were grown on SiO2 and BaF2 substrates at room temperature using molecular beam epitaxy. Metallic layers with thicknesses of 0.2 nm were alternately deposited at room ... [more ▼]

Sb2Te3 and Bi2Te3 thin films were grown on SiO2 and BaF2 substrates at room temperature using molecular beam epitaxy. Metallic layers with thicknesses of 0.2 nm were alternately deposited at room temperature and the films were subsequently annealed at 250A degrees C for 2 h. x-Ray diffraction and energy-filtered transmission electron microscopy (TEM) combined with high-accuracy energy-dispersive x-ray spectrometry revealed stoichiometric films, grain sizes of less than 500 nm, and a texture. High-quality in-plane thermoelectric properties were obtained for Sb2Te3 films at room temperature, i.e., low charge carrier density (2.6 x 10(19) cm(-3)), large thermopower (130 V K-1), large charge carrier mobility (402 cm(2) V-1 s(-1)), and resulting large power factor (29 W cm(-1) K-2). Bi2Te3 films also showed low charge carrier density (2.7 x 10(19) cm(-3)), moderate thermopower (-153 V K-1), but very low charge carrier mobility (80 cm(2) V-1 s(-1)), yielding low power factor (8 W cm(-1) K-2). The low mobilities were attributed to Bi-rich grain boundary phases identified by analytical energy-filtered TEM. [less ▲]

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See detailRoom-temperature MBE deposition, thermoelectric properties, and advanced structural characterization of binary Bi2Te3 and Sb2Te3 thin films
Peranio, Nicola; Winkler, Markus; Bessas, Dimitrios ULiege et al

in Journal of Alloys and Compounds (2012), 521

Sb2Te3 and Bi2Te3 thin films were grown at room temperature on SiO2 and BaF2 substrates using molecular beam epitaxy. A layer-by-layer growth was achieved such that metallic layers of the elements with 0 ... [more ▼]

Sb2Te3 and Bi2Te3 thin films were grown at room temperature on SiO2 and BaF2 substrates using molecular beam epitaxy. A layer-by-layer growth was achieved such that metallic layers of the elements with 0.2 nm thickness were deposited. The layer structure in the as-deposited films was confirmed by X-ray diffraction and was seen more clearly in Sb2Te3 thin films. Subsequent annealing was done at 250 degrees C for 2 h and produced the Sb2Te3 and Bi2Te3 crystal structure as confirmed by high-energy X-ray diffraction. This preparation process is referred to as nano-alloying and it was demonstrated to yield single-phase thin films of these compounds. In the thin films a significant texture could be identified with the crystal c axis being almost parallel to the growth direction for Sb2Te3 and tilted by about 30 degrees for Bi2Te3 thin films. Inplane transport properties were measured for the annealed films at room temperature. Both films yielded a charge carrier density of about 2.6 x 10(19) cm (3). The Sb2Te3 films were p-type, had a thermopower of +130 mu V K-1, and surprisingly high mobilities of 402 cm(2) V-1 s(-1). The Bi2Te3 films were n-type, showed a thermopower of -153 mu V K-1, and yielded significantly smaller mobilities of 80 cm(2) V-1 s(-1). The chemical composition and microstructure of the films were investigated by transmission electron microscopy (TEM) on cross sections of the thin films. The grain sizes were about 500 nm for the Sb2Te3 and 250 nm for the Bi2Te3 films. In the Bi2Te3 thin film, energy-filtered TEM allowed to image a Bi-rich grain boundary phase, several nanometers thick. This secondary phase explains the poor mobilities of the Bi2Te3 thin film. With these results the high potential of the nano-alloying deposition technique for growing films with a more complex layer architecture is demonstrated. (C) 2012 Elsevier B.V. All rights reserved. [less ▲]

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