DOI•
Morphological, Structural, and Compositional Characterization of Electrodeposited Bi(1-x)Sb(x) Nanowires
01 Jan 2012-
TL;DR: In this article, the influence of the electrolyte and the deposition potential on the electrochemical deposition of Bi$1-x}$Sb$_x$ nanowires in polymer templates made of polycarbonate (PC) and poly(ethylene terephthalate) (PET) was investigated.
Abstract: Bi$_{1-x}$Sb$_x$ nanowires with controlled diameter ($20$ to $200$,nm) and composition over a wide range from $x = 0$ to $05$ and $x=1$ were fabricated by electrochemical deposition in etched ion-track templates These nanowires are interesting for the investigation of the influence of quantum-size effects on the thermoelectric efficiency The influence of the electrolyte and the deposition potential on the electrochemical deposition of Bi$_{1-x}$Sb$_x$ nanowires in polymer templates made of polycarbonate (PC) and poly(ethylene terephthalate) (PET) was investigated Composition, crystalline orientation, and crystallite size of the nanowires were measured using X-ray diffraction and scanning and transmission electron microscopy It was demonstrated that the composition of the nanowires can be adjusted by the concentrations of bismuth and antimony in the electrolyte and the deposition potential Nanowires grown in PET exhibited a pronounced surface roughness compared to the nanowires deposited in PC and offer a novel possibility for the structuring of the nanowire surface to increase the thermoelectrical efficiency by enhanced phonon surface scattering Seebeck coefficient and temperature dependence of the resistance of nanowire arrays were measured in a cryostat for temperatures down to $sim 30$,K The absolute value of the Seebeck coefficient decreased with decreasing temperature and was lower than the value of the respective bulk material
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13 citations
Dissertation•
30 May 2018
TL;DR: In this article, the fabrication and characterization of Bi(1-x)Sb(x) nanowire assemblies with well-controlled and systematically adjusted wire diameter, composition, and vertical or tilted geometrical alignment are presented.
Abstract: This thesis presents the fabrication and characterization of Bi(1-x)Sb(x) nanowire assemblies with wellcontrolled and systematically adjusted wire diameter, composition, and vertical or tilted geometrical alignment. The nanowire assemblies were fabricated by means of ion-track technology combining chemical etching of ion-irradiated polymer membranes with electrodeposition of Bi and Sb into track-etched nanochannels. By systematic variation of the etching and deposition conditions, including pulsed potential
parameters and surfactant concentration in the electrolyte, the fabrication process was optimized yielding homogeneously grown, uniform nanowire assemblies and networks. The influence of the deposition parameters on morphology and crystalline structure of the resulting Bi, Sb and Bi(1-x)Sb(x) nanowires and networks was investigated by means of X-ray diffraction, high resolution transmission and scanning
electron microscopy. Seebeck coefficient and electrical resistance of the nanowire assemblies were investigated
in detail as a function of nanowire diameter and temperature. The results confirm the p- and n-type
behavior of the Sb and Bi nanowires and provide evidence of the influence of size effects on the thermoelectric
transport properties. In addition, a method to measure all relevant thermoelectrical cross-plane properties to deduce the thermoelectric efficiency of a given nanowire assembly was developed. This includes the measurement of the electrical and thermal conductivity as well as the Seebeck coefficient of a nanowire assembly. Finally, more complex nanowire systems were fabricated by combining ion-track
nanotechnology and microtechnology to prepare thermocouples formed by Sb and Bi nanowire arrays. These three-dimensional nanowire assemblies of parallel or interconnected nanowires with adjustable diameter and density, embedded in polymer templates, are of great interest for future implementation as e.g. flexible infrared sensors.
6 citations
Cites background from "Morphological, Structural, and Comp..."
...Similar behavior for Sb nanowires and thin films has already been reported in literature [200, 190, 188, 152, 20]....
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...5: Transport properties as a function of charge carrier density [117, 152]...
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...In the case of the studied nanowire assembles, it should be mentioned that the measured values always show an average of the sample since a large number of wires are contacted simultaneously, and nanowires grown in multipores can influence the results [68, 152]....
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Dissertation•
01 Jan 2003
TL;DR: In this paper, a theoretical framework for predicting the electrical properties of superlattice nanowires is presented, taking into account the effects of cylindrical wire boundary, multiple and anisotropic carrier pockets, and non-parabolic dispersion relations.
Abstract: This thesis involves an extensive experimental and theoretical study of the thermoelectric-related transport properties of Bii_2Sb. nanowires, and presents a theoretical framework for predicting the electrical properties of superlattice nanowires. A template-assisted fabrication scheme is employed to synthesize Bi-based nanowires by pressure injecting liquid metal alloys into the hexagonally packed cylindrical pores of anodic alumina. These nanowires possess a very high crystalline quality with a diameter-dependent crystallographic orientation along the wire axis. A theoretical model for Bii_2Sb, nanowires is developed, taking into consideration the effects of cylindrical wire boundary, multiple and anisotropic carrier pockets, and non-parabolic dispersion relations. A unique semimetal-semiconductor (SM-SC) transition is predicted for these nanowires as the wire diameter decreases or as the Sb concentration increases. Also, an unusual physical phenomenon involving a very high hole density of states due to the coalescence of 10 hole carrier pockets, which is especially advantageous for improving the thermoelectric performance of p-type materials, is uncovered for Bii_.2Sb_ nanowires. Various transport measurements are reported for Bi-related nanowire arrays as a function of temperature, wire diameter, Sb content, and magnetic field. R(T) measurements show distinct T dependences for semimetallic and semiconducting nanowires, as predicted by the theory, and the condition for the SM-SC transition can be clearly identified. Enhanced thermopower is observed for Bii_,Sb, nanowires as the diameter decreases or as the Sb content increases, indicating that both quantum confinement effects and Sb alloying effects are important for improving the thermoelectric performance. The theoretical model is further extended to study transport properties of Te-doped Bi nanowires and Sb nanowires, and good agreement between theoretical predictions and experimental results is obtained. A model for superlattice nanowires is presented to evaluate their potential for thermoelectric applications. Thermoelectric properties of superlattice nanowires made of various lead salts (PbS, PbSe, and PbTe) are investigated as a function of segment length, wire diameter, crystal orientation along the wire axis, and length ratio of
1 citations
TL;DR: In this paper , the authors present temperature-dependent Seebeck coefficient and relative electrical resistance measurements of parallel bismuth nanowire arrays with diameters between 40 and 400 nm synthesized by pulsed electroplating in polymer templates.
Abstract: The electrical transport in bismuth nanowires is strongly influenced by both sample geometry and crystallinity. Compared to bulk bismuth, the electrical transport in nanowires is dominated by size effects and influenced by surface states, which gain increasing relevance with increasing surface-to-volume ratios, i.e. with decreasing wire diameter. Bismuth nanowires with tailored diameter and crystallinity constitute, therefore, excellent model systems, allowing to study the interplay of the different transport phenomena. Here, we present temperature-dependent Seebeck coefficient and relative electrical resistance measurements of parallel bismuth nanowire arrays with diameters between 40 and 400 nm synthesized by pulsed electroplating in polymer templates. Both electrical resistance and Seebeck coefficient exhibit a non-monotonic temperature dependence, with the sign of the Seebeck coefficient changing from negative to positive with decreasing temperature. The observed behavior is size-dependent and is attributed to limitations of the mean free path of the charge carriers within the nanowires. The observed size-dependent Seebeck coefficient and in particular the size-dependent sign change opens a promising avenue for single-material thermocouples with p- and n-legs made from nanowires with different diameters.
References
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TL;DR: An exact derivation of the Scherrer equation is given for particles of spherical shape, values of the constant for half-value breadth and for integral breadth being obtained in this article, and various approximation methods which have been used are compared with the exact calculation.
Abstract: An exact derivation of the Scherrer equation is given for particles of spherical shape, values of the constant for half-value breadth and for integral breadth being obtained. Various approximation methods which have been used are compared with the exact calculation. The tangent plane approximation of v. Laue is shown to be quite satisfactory, but some doubt is cast on the use of approximation functions. It is suggested that the calculation for the ellipsoidal particle based on the tangent plane approximation will provide a satisfactory basis for future work.
6,907 citations
Book•
01 Jan 1996
TL;DR: In this article, the transmission electron microscope (TEM) is used to detect X-ray spectra and images using a combination of parallel-beam diffraction patterns and CBED patterns.
Abstract: Basics.- The Transmission Electron Microscope.- Scattering and Diffraction.- Elastic Scattering.- Inelastic Scattering and Beam Damage.- Electron Sources.- Lenses, Apertures, and Resolution.- How to 'See' Electrons.- Pumps and Holders.- The Instrument.- Specimen Preparation.- Diffraction.- Diffraction in TEM.- Thinking in Reciprocal Space.- Diffracted Beams.- Bloch Waves.- Dispersion Surfaces.- Diffraction from Crystals.- Diffraction from Small Volumes.- Obtaining and Indexing Parallel-Beam Diffraction Patterns.- Kikuchi Diffraction.- Obtaining CBED Patterns.- Using Convergent-Beam Techniques.- Imaging.- Amplitude Contrast.- Phase-Contrast Images.- Thickness and Bending Effects.- Planar Defects.- Imaging Strain Fields.- Weak-Beam Dark-Field Microscopy.- High-Resolution TEM.- Other Imaging Techniques.- Image Simulation.- Processing and Quantifying Images.- Spectrometry.- X-ray Spectrometry.- X-ray Spectra and Images.- Qualitative X-ray Analysis and Imaging.- Quantitative X-ray Analysis.- Spatial Resolution and Minimum Detection.- Electron Energy-Loss Spectrometers and Filters.- Low-Loss and No-Loss Spectra and Images.- High Energy-Loss Spectra and Images.- Fine Structure and Finer Details.
2,679 citations
TL;DR: Calculations show that this approach has the potential to achieve a significant increase in the figure of merit over both the bulk value and the calculated two-dimensional superlattice values.
Abstract: We investigate the effect on the thermoelectric figure of merit of preparing materials in the form of one-dimensional conductors or quantum wires. Our calculations show that this approach has the potential to achieve a significant increase in the figure of merit over both the bulk value and the calculated superlattice values.
2,416 citations
"Morphological, Structural, and Comp..." refers background in this paper
...In 1993, Hicks and Dresselhaus proposed a new route to efficient thermoelectric materials via nanosized quantum-wells(4,5) or nanowires.(6,7)...
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...and quantized energy levels for the charge carriers.(4,6) The properties σ, S, and κ derived by regarding two bands can be represented by a set of functions Ki, which can be defined as follows:(2) Ki = − 2T Nm∗ ∫ ∞...
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IBM1
TL;DR: In this paper, the total resistivity of a thin metal film is calculated from a model in which three types of electron scattering mechanisms are simultaneously operative: an isotropic background scattering (due to the combined effects of phonons and point defects), scattering due to a distribution of planar potentials (grain boundaries), and scattering by the external surfaces.
Abstract: In this paper, the total resistivity of a thin metal film is calculated from a model in which three types of electron scattering mechanisms are simultaneously operative: an isotropic background scattering (due to the combined effects of phonons and point defects), scattering due to a distribution of planar potentials (grain boundaries), and scattering due to the external surfaces. The intrinsic or bulk resistivity is obtained by solving a Boltzmann equation in which both grain-boundary and background scattering are accounted for. The total resistivity is obtained by imposing boundary conditions due to the external surfaces (as in the Fuchs theory) on this Boltzmann equation. Interpretation of published data on grain-boundary scattering in bulk materials in terms of the calculated intrinsic resistivity, and of thin-film data in terms of the calculated total resistivity suggests that (i) the grain-boundary reflection coefficient in Al is \ensuremath{\approx} 0.15, while it is somewhat higher in Cu; (ii) the observed thickness dependence of the resistivity in thin films is due to grain-boundary scattering as well as to the Fuchs size effect; and (iii) the common observation that single-crystal films possess lower resistivities than polycrystalline films may be accounted for by grain-boundary effects rather than by differences in the nature of surface scattering.
1,842 citations
"Morphological, Structural, and Comp..." refers methods in this paper
...Two models describe these effects, namely the model of Dingle for scattering at the surface,(84) and the model of Mayadas and Shatzkes for scattering at grain boundaries.(85) In 1937, Fuchs calculated the influence of additional scattering of charge carriers at the surface of thin films....
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01 Jan 1938
TL;DR: In this paper, the conductivity of thin films of the alkali metals has been measured in the H. W. Wills Physical Laboratory, Bristol and the experimental results were compared with a formula derived on the basis of this hypothesis.
Abstract: The conductivity of thin films of the alkali metals has recently been measured in the H. W. Wills Physical Laboratory, Bristol*. It was found that as the thickness of the film is decreased to that of a few atomic layers the conductivity drops below that of the bulk metal. In the papers quoted the hypothesis was put forward that this effect is due to the shortening of the mean free paths of the conduction electrons of the metal by collisions with the boundaries of the film. The experimental results were compared with a formula derived on the basis of this hypothesis. This formula was, however, obtained subject to a number of simplifying assumptions, and it is the first purpose of this paper to obtain a more accurate formula. I also compare this formula with experiment, and make certain deductions about the surfaces of thin films.
1,812 citations
"Morphological, Structural, and Comp..." refers background in this paper
...In 1937, Fuchs calculated the influence of additional scattering of charge carriers at the surface of thin films.(86) Twenty-two years later, Dingle applied the theoretical considerations to thin wires with a circular cross-section and a spherical Fermi surface....
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