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Thesis (M.Sc.) -- University of Toronto, 1994.
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Download CdS band gap measurement of bulk and nanowires using resonance Raman spectroscopy
Nanowires (NWs) are filamentary crystals with diameters of tens of nanometers and lengths of few microns. Semiconductor NWs have recently attracted a great interest, because they are emerging as building blocks for novel nanoscale devices. Since physical properties are size dependent, NWs display novel properties with respect to their bulk counterparts.
Raman scattering is a nondestructive Author: Marta De Luca, Ilaria Zardo. Electronic Band Structure of Wurtzite GaP Nanowires via Resonance Raman Spectroscopy Article (PDF Available) in Applied Physics Letters (2) July with Reads How we measure 'reads'.
Raman spectroscopy and Resonance Raman spectroscopy are well-established techniques that are widely exploited scientifically and technologically.
Whilst first reported by Raman himself in 1 the key to wide spread use of Raman spectroscopy was the development of lasers, tunable lasers in the case of Resonance Raman, to provide high. We report the graded electronic band gap along the axis of individual heterostructured WZ-ZB InAs/InSbAs nanowires.
Resonance Raman imaging has been exploited to. Resonant Raman scattering (RRS) was used to probe the electronic states of CdS nanowires (∼10nm diameter) grown by chemical vapor deposition.
Individual Ar+ laser lines were used to vary the excitation energy while observing scattering from CdS phonons; strong 1-longitudinal optical (LO) and 2-LO Raman resonances were readily observed within the broader photoluminescence Cited by: nanowires. Specifically, Raman spectroscopy, aided by mass spectrometry, was used to identify unintentional impurities in ZnO and GaN nanowires and their incorporation route.
Phonon dynamics, in particular the enharmonic phonon coupling strength, was also studied by Raman spectroscopy. temperature dependence of the band-edge for bulk CdS single crystals as measured by Imada and collaborators.8 The temperature dependence of both the bulk CdS band-edge and the nanowire NBE energy were fit to the extended phenomenological Varshni equation 9 3 4 0 T T Eg E + = − β α.
Strongly confined nano-systems, such as one-dimensional nanowires, feature deviations in their structural, electronic and optical properties from the corresponding bulk.
In this work, we investigate the behavior of long-wavelength, optical phonons in vertical arrays of InAs nanowires by Raman spectroscopy. We attribute the main changes in the spectral features to thermal Cited by: Resonance Raman spectroscopy 17 is an ideal tool both for understanding the fundamental physics of extreme nanowires and, once the resonance energies have been determined, for characterizing the type and quality of samples of by: 1.
A complete Raman study of GaP nanowires is presented. By comparison with the Raman spectra of GaP bulk material, microcrystals and nanoparticles, we give evidence that the Raman spectrum is affected by the one-dimensional shape of the nanowires. The Raman spectrum is sensitive to the polarization of the laser light.
A specific shape of the overtones located between and cm Cited by: 5. Introduction. The study of nano-particles has generated a tremendous amount of interest recently because of their novel properties and wide-ranging potential applications 1, 2, nce Raman spectroscopy is one of the techniques that has been used to study CdS band gap measurement of bulk and nanowires using resonance Raman spectroscopy book, in particular CdS 4, 5, 6, ly, Routkevitch et al.
8, 9have fabricated CdS nanowires in porous anodic Cited by: nanowires (NWs) are expected to contain large strain fields due to the lattice-mismatch at the core/shell interface. Here we report the measurement of core strain in a NW heterostructure using Raman spectroscopy.
We compare the Raman spectra, and the frequency of the Ge-Ge mode measured in individual Ge-Si Ge core-shell, and bare Ge NWs. Fig. 3 presents the room-temperature Raman spectrum of the CdS nanowires array excited by the laser with nm wavelength.
Two stronger peaks can be observed and located at cm −1 and cm −1, which are ascribed to the first-order and second-order longitudinal optic (LO) phonon modes of CdS, the bulk CdS, the 1LO and 2LO phonon peaks should be located at cm −1 Cited by: We present recent developments in Raman probe of confined optical and acoustic phonons in nonpolar semiconducting nanowires, with emphasis on Si and Ge.
First, a review of the theoretical spatial correlation phenomenological model widely used to explain the downshift and asymmetric broadening to lower energies observed in the Raman profile is by: Raman Spectroscopy on Semiconductor Nanowires, Nanowires, Paola Prete, IntechOpen, DOI: / Available from: Ilaria Zardo, Gerhard Abstreiter and Anna Fontcuberta i Cited by: 2.
Time-resolved photoluminescence (PL) and micro-PL imaging were used to study single CdS nanowires at 10K. The low-temperature PL of all CdS nanowires exhibits spectral features near energies associated with free and bound exciton transitions, with the transition energies and emission intensities varying along the length of the nanowire.
In addition, several nanowires show spatially localized Cited by: nanowires were intentionally bent with an atomic force microscope and variations in the optical phonon frequency along the wires were mapped using Raman spectroscopy. Sections of the nanowires with a high curvature showed signiﬁcantly broadened phonon lines.
58 nanowires. It is well known that Raman spectroscopy is a non-destructive method for material characterization. However, a noticeable problem in testing Raman spectra is to remove the thermal effect. When irradiated by a focussed laser beam, the local temperature of the sample can reach several hundred (a) (b) (c) Figure 5.
(a) Raman. short-range EM coupling between nanowires. Surface-enhanced Raman spectroscopy (SERS) is a powerful tool for chemical analysis with its molecular specificity and extraordinary sensitivity capable of single-molecule detection.
For molecules adsorbed to nanostructured metal surfaces, Raman cross sections have been reported to increase by ,2 In. The influence of GaN nanowires on the optical and electrical properties of graphene deposited on them was studied using Raman spectroscopy and a microwave-induced electron transport method.
It was found that the interaction with the nanowires induces spectral changes and leads to a significant enhancement of the Raman scattering intensity.
Time-resolved photoluminescence (PL) and micro-PL imaging were used to study single CdS nanowires at 10 K. The low-temperature PL of all CdS nanowires exhibits spectral features near energies associated with free and bound exciton transitions, with the transition energies and emission intensities varying along the length of the by: Raman spectrum of a SiGe NW (a), Raman spectrum of the NW and Raman spectrum of a bulk Si sample, showing the strong resonance of the NW signal (b).
(excitation nm) A typical Raman spectrum obtained in a SiGe NW with nm excitation is shown in Figa. It presents the typical bands corresponding to Ge-Ge, Si-Si and Si-Ge bonds. Raman spectroscopy has emerged as a powerful and important characterisation tool for probing molecular semiconducting materials.
The useful optoelectronic properties of these materials arise from the delocalised π-electron density in the conjugated core of the molecule, which also results in large Raman scattering cross-sections and a strong coupling between its electronic states and Cited by: Semiconductor nanowires, due to their unique electronic, optical, and chemical properties, are firmly placed at the forefront of nanotechnology research.
The rich physics of semiconductor nanowire optics arises due to the enhanced light–matter interactions at the nanoscale and coupling of optical modes to electronic resonances.
Furthermore, confinement of light can be taken to new extremes Cited by: 8. dent confocal Raman spectroscopy on single carbon nano-tubes and/or nanowires indicates that the physics behind Ra-man scattering of such one-dimensional nanostructures can differ signiﬁcantly from the bulk.
Indeed, the highly aniso-tropic shape of the nanowires can lead to angular dependen-cies of the modes, which otherwise would not be expected.
Uniform nanogaps were produced in silver nanowires previously fabricated by AC electrodeposition in porous anodic alumina templates and released by dissolving the oxide matrix. Configuring the nanowires with electrodes and passing current through them created nanogaps by electromigration.
Uniform nanogaps approximately perpendicular to the axes of the nanowires were produced with widths in the Cited by: Surface plasmon resonance (SPR) is the resonant oscillation of conduction electrons at the interface between negative and positive permittivity material stimulated by incident light.
SPR is the basis of many standard tools for measuring adsorption of material onto planar metal (typically gold or silver) surfaces or onto the surface of metal nanoparticles. Materials and Methods.
The bandgap-graded CdS x Se 1−x nanowires were grown on sapphire substrate by a source-moving chemical vapor deposition technique, which employed a specially designed horizontal tube furnace.
The detailed growth processes were described in previous report The carrier dynamics and photoconductivity were investigated using OPTP by: 5. Silver nanowires (AgNWs) were chemically etched to significantly increase the surface roughness and then self-assembled on the liquid/gas interfaces via the interfacial assembly method to obtain aligned chemically etched silver nanowire films.
The as-fabricated silver nanowire films were used as novel surface-enhanced Raman scattering (SERS) by: 4. carried out with a home-built Raman spectroscopy system on an inverted microscope (Eclipse Ti-U, Nikon, Japan) equipped with a dark-field condenser ( Spatially-Resolved Imaging and Temperature Dependence of Single CdS Nanowire Photoluminescence Thang B.
Hoang 1, L. Titova 1, L. Smith 1 and H. Jackson 1 J. Yarrison-Rice 2, J. Lensch 3 and L. Lauhon 3 1Department of Physics, University of Cincinnati, Cincinnati, OH 2 Department of Physics, Miami University, OH 3 Department of Mat. Sci. and Engineering, Northwestern.
OPTICAL SPECTROSCOPY OF WIDE-BAND-GAP SEMICONDUCTORS: RAMAN AND PHOTOLUMINESCENCE OF GALLIUM NITRIDE, ZINC OXIDE AND THEIR NANOSTRUCTURES Dake Wang Doctor of Philosophy, Decem (B.S. Sichuan University, Chengdu, China, August ) Typed Pages Directed by Minseo Park.
Si Nanowires for spectroscopy. Christiansen, M. Becker, V. Sivakov, and G. Andrae. Silicon nanowires grown by the vapor-liquid-solid (VLS) growth mechanism with gold as the catalyst show gold caps ~50 nm – nm in diameter with an almost ideal hemispherical shape atop a silicon column.
The second part of the thesis focused on the assessment of free carriers by Raman spectroscopy in systems with an expected high electron mobility: GaAs nanowires with a modulation doped structure and InAs(Sb) nanowires.
Raman measurements were performed as a function of the temperature on modulation doped GaAs/AlGaAs : Francesca Amaduzzi. 1 INTRODUCTION. A perspective review of the field of Raman spectroscopy is published annually in the Journal of Raman Spectroscopy (JRS), first initiated in 1 and continued throughin which highlights of current trends in Raman spectroscopy are presented.
The scope of the current review incudes papers published in the JRS during calendar year as well as a survey of Raman Cited by: 4. FIG. Raman spectra for SiNW’s with diameter of 10, 15, and 21 nm and for bulk c-Si.~b.
Full proﬁle of a Raman spectrum of the SiNW’s with a diameter of 10 nm and its decomposition. The solid line represents the recorded Raman spectrum, and the dashed lines are its decomposition. 16 WANG, ZHOU, LIU, PAN, ZHANG, YU, AND ZHANG PRB The structural and electronic properties of (10 0) faceted CdTe nanowires with hexagonal or triangular cross sections were investigated using the self-consistent-charge density-functional tight-binding (SCC-DFTB) method.
The formation energies and band gap of CdTe nanowires are studied as a function of both nanowire size and surface atom ratio. The atomic relaxations of the surface of the (10 Cited by: In Fig. 3 we show the absorption dependence on NW length, using the geometric cross section parameters from the fabrication of Samples A-D.
Cited by: We present a noninvasive optical method to determine the local strain in individual semiconductor nanowires. InP nanowires were intentionally bent with an atomic force microscope and variations in the optical phonon frequency along the wires were mapped using Raman spectroscopy.
Sections of the nanowires with a high curvature showed significantly broadened phonon lines. High densities of Au- and Mncatalyzed self-assembled GaAs nanowires (NWs) with diameter in the range of 20 to nm and length of few microns were synthesized by molecular beam epitaxy (MBE) on different substrates at varied substrate temperatures.
These nanowires were investigated by means of μ-Raman spectroscopy at room by: 4. The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency.
Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure Cited by: CdSe, nanowires, photoluminescence 1. Introduction Direct band-gap semiconductor nanowires (NWs) have great potential for nano-photonic devices [1–3], including solar cells [4, 5], light emitting diodes , and photodetectors .
CdSe is particularly interesting .uted to the band gap emission ( eV at room tempera-ture). The tapered CdS nanobelts and CdSe nanowires with high-quality optical property should be good building blocks for photonic devices.
Conclusions In summary, tapered CdS nanobelts and CdSe nanowires were prepared by hydrogen-assisted thermal evaporation by: