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Static analysis of tapered nanowires based on nonlocal Euler-Bernoulli beam theory via differential quadrature method

Janghorban,Maziar
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2012 EN
Relevância na Pesquisa
56.83%
As a first endeavor, bending analysis of tapered nano wires with circular cross section is investigated. In this research, nonlocal elasticity theory based on Euler-Bernoulli beam theory is used to formulate the equations. Differential quadrature method (DQM) is employed to solve the governing equations. Different parameters such as nonlocal parameter, length and radius of tapered nano wires are also considered. The results of present work can be used as bench marks for future works.

Synthesis of Tapered CdS Nanobelts and CdSe Nanowires with Good Optical Property by Hydrogen-Assisted Thermal Evaporation

Wang, Min; Fei, GuangTao
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 10/07/2009 EN
Relevância na Pesquisa
27%
The tapered CdS nanobelts and CdSe nanowires were prepared by hydrogen-assisted thermal evaporation method. Different supersaturation leads to two different kinds of 1D nanostructures. The PL measurements recorded from the as-prepared tapered CdS nanobelts and CdSe nanowires show only a bandgap emission with relatively narrow full-width half maximum, which means that they possess good optical property. The as-synthesized high-quality tapered CdS nanobelts and CdSe nanowires may be excellent building blocks for photonic devices.

Investigation of Nucleation Mechanism and Tapering Observed in ZnO Nanowire Growth by Carbothermal Reduction Technique

Kar, Ayan; Low, Ke-Bin; Oye, Michael; Stroscio, Michael A; Dutta, Mitra; Nicholls, Alan; Meyyappan, M
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 19/08/2010 EN
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26.5%
ZnO nanowire nucleation mechanism and initial stages of nanowire growth using the carbothermal reduction technique are studied confirming the involvement of the catalyst at the tip in the growth process. Role of the Au catalyst is further confirmed when the tapering observed in the nanowires can be explained by the change in the shape of the catalyst causing a variation of the contact area at the liquid–solid interface of the nanowires. The rate of decrease in nanowire diameter with length on the average is found to be 0.36 nm/s and this rate is larger near the base. Variation in the ZnO nanowire diameter with length is further explained on the basis of the rate at which Zn atoms are supplied as well as the droplet stability at the high flow rates and temperature. Further, saw-tooth faceting is noticed in tapered nanowires, and the formation is analyzed crystallographically.

Bright single-photon sources in bottom-up tailored nanowires

Reimer, Michael E.; Bulgarini, Gabriele; Akopian, Nika; Hocevar, Moïra; Bavinck, Maaike Bouwes; Verheijen, Marcel A.; Bakkers, Erik P.A.M.; Kouwenhoven, Leo P.; Zwiller, Val
Fonte: Nature Pub. Group Publicador: Nature Pub. Group
Tipo: Artigo de Revista Científica
Publicado em 13/03/2012 EN
Relevância na Pesquisa
26.5%
The ability to achieve near-unity light-extraction efficiency is necessary for a truly deterministic single-photon source. The most promising method to reach such high efficiencies is based on embedding single-photon emitters in tapered photonic waveguides defined by top-down etching techniques. However, light-extraction efficiencies in current top-down approaches are limited by fabrication imperfections and etching-induced defects. The efficiency is further tempered by randomly positioned off-axis quantum emitters. Here we present perfectly positioned single quantum dots on the axis of a tailored nanowire waveguide using bottom-up growth. In comparison to quantum dots in nanowires without waveguides, we demonstrate a 24-fold enhancement in the single-photon flux, corresponding to a light-extraction efficiency of 42%. Such high efficiencies in one-dimensional nanowires are promising to transfer quantum information over large distances between remote stationary qubits using flying qubits within the same nanowire p–n junction.

Silicon nanowires: where mechanics and optics meet at the nanoscale

Ramos, Daniel; Gil-Santos, Eduardo; Malvar, Oscar; Llorens, Jose M.; Pini, Valerio; Paulo, Alvaro San; Calleja, Montserrat; Tamayo, Javier
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 06/12/2013 EN
Relevância na Pesquisa
26.61%
Mechanical transducers based on nanowires promise revolutionary advances in biological sensing and force microscopy/spectroscopy. A crucial step is the development of simple and non-invasive techniques able to detect displacements with subpicometer sensitivity per unit bandwidth. Here, we design suspended tapered silicon nanowires supporting a range of optical resonances that confine and efficiently scatter light in the visible range. Then, we develop an optical method for efficiently coupling the evanescent field to the regular interference pattern generated by an incoming laser beam and the reflected beam from the substrate underneath the nanowire. This optomechanical coupling is here applied to measure the displacement of 50 nm wide nanowires with sensitivity on the verge of 1 fm/Hz1/2 at room temperature with a simple laser interferometry set-up. This method opens the door to the measurement of the Brownian motion of ultrashort nanowires for the detection of single biomolecular recognition events in liquids, and single molecule spectroscopy in vacuum.

Enhanced optical confinement and lasing characteristics of individual urchin-like ZnO microstructures prepared by oxidation of metallic Zn

Lu, Chia-Hao; Chao, Tzu-Yang; Chiu, Ying-Feng; Tseng, Shuo-Yen; Hsu, Hsu-Cheng
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 11/04/2014 EN
Relevância na Pesquisa
26.18%
We prepared urchin-like micron-sized ZnO cavities with high optical quality by oxidizing metallic Zn and proposed the mechanism that resulted in the growth of the urchin-like microstructures. The photoluminescence spectra of the ZnO microstructures had a predominant excitonic emission at room temperature. The lasing properties of the urchin-like ZnO microstructures were investigated systematically through excitation power- and size-dependent photoluminescence measurements. The results showed that a low lasing threshold with high quality factors could be achieved because of the high reflectivity of the optical reflectors formed by the tapered nanowires. The unique optical characteristics may facilitate the development of high-efficiency random lasers.

Designing Novel Semiconductor Nanowire Structures: Synthesis and Fabrication for Localized Photodetection and Sensing

Gao, Ruixuan
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
Relevância na Pesquisa
16.88%
Semiconductor nanowires display a wide range of structural and functional diversity, and as such provide a platform for nanomaterials research. At present, a number of nanowire structural motifs have been discovered and configured into devices with unique electrical and optical functionalities. For example, a kinked nanowire with a localized axial dopant modulation can record intracellular action potentials when incorporated into a three dimensional device. A radially modulated p-i-n nanowire can function as a nanoscale photovoltaic device to power logic gates and sensors. This thesis focuses on novel electrical and optical device functionalities based on rational design, synthesis and characterization of semiconductor nanowire structures for applications in the physical, chemical and biological sciences. First, I will present the design, synthesis and fabrication of two nanodevices for intracellular sensing that are based on core/shell and branched nanowire structural motifs. In both types of devices, a nanotube bridge templated by nanowires conducts the intracellular electrical and chemical potentials to the gating regions and the change in potential is recorded as the change of the device conductance. Both nanowire-based devices can sense extra- and intracellular action potentials with high spatial resolution. Furthermore...

Small diameter nano- and micro-wire tapers in single mode fibre

Clohessy, A. M.; Healy, Noel; Murphy, Dominic F.; Hussey, Conleth D.
Fonte: IEEE Publicador: IEEE
Tipo: Conference paper
Publicado em //2005 EN
Relevância na Pesquisa
26.42%
Prompted by the recent interest in nano-wires, this paper reports on the successful production of very small diameter (submicron), low-loss tapers in single mode fibre. This approach gives a convenient single mode launch into the tapered waveguide or micro-wire and conserves the single mode throughout the structure. Results from couplers fabricated by twisting two such structures together and other related phenomena are reported.; A.M. Clohessy, N. Healy, D.F. Murphy and C.D. Hussey

Engineering Application-Specific Plasmonic Nanoparticles: Quantitative Measurements and Precise Characterization

Anderson, Lindsey
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
16.39%
Nobel metal nanoparticles that exhibit plasmon resonances in the visible and near infrared have been of great interest in recent years. Strong light-matter interactions on the nanoscale have a range of interesting properties that may be useful in applications in medicine, sensing, solar energy harvesting and information processing. Depending on the application, particle materials and geometries can be optimized for performance. A novel method of quantifying individual nanoparticle scattering cross-sections by comparing experiments with analytical theory for gold nanospheres is proposed and utilized. Results show that elongated particles scatter very brightly for their volumes. This brightness is due to a strong longitudinal plasmon resonance that occurs in the near infrared – where gold has minimal loss. Elongated particles, such as nanorods, are therefore, ideal for applications that rely on particles scattering brightly in small spaces, such as biological imaging. Next, gold nanobelts are discussed and characterized. These novel structures are akin to nanowires, but with a small, rectangular cross-sectional geometry. Gold nanobelts are shown to exhibit a strong transverse resonance that has never been reported previously in nanowires. The transverse resonance is shown to shift linearly with crosssectional aspect ratio. Other interesting products from the nanobelt synthesis...

Near field imaging of gallium nitride nanowires for characterization of minority carrier diffusion

Baird, Lee G.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
Relevância na Pesquisa
26.57%
Approved for public release, distribution unlimited; A novel system has been developed for the imaging of carrier transport within semiconductor nanostructures by operating a near field scanning optical microscopy (NSOM) within a scanning electron microscope. Luminescence associated with carrier recombination is collected with high spatial resolution to monitor the motion and recombination of charge generated by use of an electron beam as an independent point source. Light is collected in the near field from a scanning fiber using tuning fork feedback in an open architecture combined AFM/NSOM system allowing for independent motion of sample and tip. From a single image, it is possible to obtain a direct measure of minority carrier diffusion length. This technique has been used in the near-field collection mode to image the diffusion of holes in n-type GaN-AlGaN coreshell nanowires, unintentionally doped GaN nanowires and p-type GaN nanowires grown via Ni-catalyzed MOCVD. Measurements were made on tapered anowires ranging in diameter from 500 to 800 nm, with lengths up to ~ 30 ?m. The average 1-dimensional carrier diffusion length was measured to be 1.3 +/- 0.2 ?m for GaN/AlGaN core-shell, 0.96 +/- 0.25 ?m for the uncoated GaN wires...

Si-Doped Ceramic Al4O4C Nanowires: Full-Color Emission and Optical Waveguide Behavior

Sun, Y.; Lei, H. X.; Cui, H.; Yang, G. W.; Li, B. J.; Wang, C. X.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 30/10/2014 EN
Relevância na Pesquisa
26.18%
The increasing prosperity of the photonics field has hastened the development of several sub-disciplines, with the aim to create advanced photonic devices, produce photonic circuits and eventually enable all-optical communication. This development has resulted in the demand for micro-nano-sized functional units with specific space dimensions (1D & 2D) for subwavelength photon operation purposes. The fundamental task involves a search for available semiconductor materials as micro-nano light sources and optical interconnections; in this regard, finding a white-light source is the most challenging task because typical band-band emission is not possible in the single phase. Using current approaches, which rely on surface-state emission and the integration of various emission components, it is impossible to achieve single-phase, single-unit components with specific space dimensions. Here, we achieved continuous full-color (ultraviolet to red) emission by engineering a single Al4O4C nanowire with Si doping, which created impurity levels in the bandgap and conduction band. High light propagation performance was also observed when blue, green and red lasers were coupled into a single nanowire using a tapered optical fiber. This novel 1D nanostructure is an excellent candidate for use in future photonic circuits as a white-light source or interconnection component.

High-precision, large-domain three-dimensional manipulation of nano-materials for fabrication nanodevices

Zou, Rujia; Yu, Li; Zhang, Zhenyu; Chen, Zhigang; Hu, Junqing
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 27/07/2011 EN
Relevância na Pesquisa
16.57%
Nanoscaled materials are attractive building blocks for hierarchical assembly of functional nanodevices, which exhibit diverse performances and simultaneous functions. We innovatively fabricated semiconductor nano-probes of tapered ZnS nanowires through melting and solidifying by electro-thermal process; and then, as-prepared nano-probes can manipulate nanomaterials including semiconductor/metal nanowires and nanoparticles through sufficiently electrostatic force to the desired location without structurally and functionally damage. With some advantages of high precision and large domain, we can move and position and interconnect individual nanowires for contracting nanodevices. Interestingly, by the manipulating technique, the nanodevice made of three vertically interconnecting nanowires, i.e., diode, was realized and showed an excellent electrical property. This technique may be useful to fabricate electronic devices based on the nanowires' moving, positioning, and interconnecting and may overcome fundamental limitations of conventional mechanical fabrication.

Diameter-dependent conductance of InAs nanowires

Scheffler, Marc; Nadj-Perge, Stevan; Kouwenhoven, Leo P.; Borgström, Magnus T.; Bakkers, Erik P. A. M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/12/2009
Relevância na Pesquisa
26.5%
Electrical conductance through InAs nanowires is relevant for electronic applications as well as for fundamental quantum experiments. Here we employ nominally undoped, slightly tapered InAs nanowires to study the diameter dependence of their conductance. Contacting multiple sections of each wire, we can study the diameter dependence within individual wires without the need to compare different nanowire batches. At room temperature we find a diameter-independent conductivity for diameters larger than 40 nm, indicative of three-dimensional diffusive transport. For smaller diameters, the resistance increases considerably, in coincidence with a strong suppression of the mobility. From an analysis of the effective charge carrier density, we find indications for a surface accumulation layer.; Comment: 9 pages, 5 figures

Optical properties of single ZnTe nanowires grown at low temperature

Artioli, Alberto; Rueda-Fonseca, Pamela; Stepanov, Petr; Bellet-Amalric, Edith; Hertog, Martien Den; Bougerol, Catherine; Genuist, Yann; Donatini, Fabrice; André, Régis; Nogues, Gilles; Kheng, Kuntheak; Tatarenko, Serge; Ferrand, David; Cibert, Joel
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/06/2013
Relevância na Pesquisa
26.67%
Optically active gold-catalyzed ZnTe nanowires have been grown by molecular beam epitaxy, on a ZnTe(111) buffer layer, at low temperature 350\degree under Te rich conditions, and at ultra-low density (from 1 to 5 nanowires per micrometer^{2}. The crystalline structure is zinc blende as identified by transmission electron microscopy. All nanowires are tapered and the majority of them are <111> oriented. Low temperature micro-photoluminescence and cathodoluminescence experiments have been performed on single nanowires. We observe a narrow emission line with a blue-shift of 2 or 3 meV with respect to the exciton energy in bulk ZnTe. This shift is attributed to the strain induced by a 5 nm-thick oxide layer covering the nanowires, and this assumption is supported by a quantitative estimation of the strain in the nanowires.

Bright single-photon sources in bottom-up tailored nanowires

Reimer, Michael E.; Bulgarini, Gabriele; Akopian, Nika; Hocevar, Moïra; Bavinck, Maaike Bouwes; Verheijen, Marcel A.; Bakkers, Erik P. A. M.; Kouwenhoven, Leo P.; Zwiller, Val
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 26/03/2012
Relevância na Pesquisa
26.5%
The ability to achieve near-unity light extraction efficiency is necessary for a truly deterministic single photon source. The most promising method to reach such high efficiencies is based on embedding single photon emitters in tapered photonic waveguides defined by top-down etching techniques. However, light extraction efficiencies in current top-down approaches are limited by fabrication imperfections and etching induced defects. The efficiency is further tempered by randomly positioned off-axis quantum emitters. Here, we present perfectly positioned single quantum dots on the axis of a tailored nanowire waveguide using bottom-up growth. In comparison to quantum dots in nanowires without waveguide, we demonstrate a 24-fold enhancement in the single photon flux, corresponding to a light extraction efficiency of 42 %. Such high efficiencies in one-dimensional nanowires are promising to transfer quantum information over large distances between remote stationary qubits using flying qubits within the same nanowire p-n junction.; Comment: 19 pages, 6 figures

Broadband and omnidirectional anti-reflection layer for III/V multi-junction solar cells

Diedenhofen, Silke L.; Grzela, Grzegorz; Haverkamp, Erik; Bauhuis, Gerard; Schermer, John; Rivas, Jaime Gómez
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/10/2012
Relevância na Pesquisa
27%
We report a novel graded refractive index antireflection coating for III/V quadruple solar cells based on bottom-up grown tapered GaP nanowires. We have calculated the photocurrent density of an InGaP-GaAs-InGaAsP-InGaAs solar cell with a MgF2/ZnS double layer antireflection coating and with a graded refractive index coating. The photocurrent density can be increased by 5.9 % when the solar cell is coated with a graded refractive index layer with a thickness of 1\mu m. We propose to realize such a graded refractive index layer by growing tapered GaP nanowires on III/V solar cells. For a first demonstration of the feasibility of the growth of tapered nanowires on III/V solar cells, we have grown tapered GaP nanowires on AlInP/GaAs substrates. We show experimentally that the reflection from the nanowire coated substrate is reduced and that the transmission into the substrate is increased for a broad spectral and angular range.; Comment: 5 Figures

Broadband Quantum Efficiency Enhancement in High Index Nanowires Resonators

Yang, Yiming; Peng, Xingyue; Hyatt, Steven; Yu, Dong
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/02/2015
Relevância na Pesquisa
26.39%
Light trapping in sub-wavelength semiconductor nanowires (NWs) offers a promising approach to simultaneously reducing material consumption and enhancing photovoltaic performance. Nevertheless, the absorption efficiency of a NW, defined by the ratio of optical absorption cross section to the NW diameter, lingers around 1 in existing NW photonic devices, and the absorption enhancement suffers from a narrow spectral width. Here, we show that the absorption efficiency can be significantly improved in NWs with higher refractive indices, by an experimental observation of up to 350% external quantum efficiency (EQE) in lead sulfide (PbS) NW resonators, a 3-fold increase compared to Si NWs. Furthermore, broadband absorption enhancement is achieved in single tapered NWs, where light of various wavelengths is absorbed at segments with different diameters analogous to a tandem solar cell. Overall, the single NW Schottky junction solar cells benefit from optical resonance, near bandgap open circuit voltage, and long minority carrier diffusion length, demonstrating power conversion efficiency (PCE) comparable to single Si NW coaxial p-n junction cells11, but with much simpler fabrication processes.

Optical absorption of silicon nanowires

Xu, Tao; Lambert, Yannick; Krzeminski, Christophe; Grandidier, Bruno; Stiévenard, Didier; Lévêque, Gaëtan; Akjouj, Abdellatif; Pennec, Yan; Djafari-Rouhani, Bahram
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/09/2012
Relevância na Pesquisa
26.5%
We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods : the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the Finite Difference Time Domain (FDTD) method is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies, that allows to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

Generation of parabolic similaritons in tapered silicon photonic wires: comparison of pulse dynamics at telecom and mid-IR wavelengths

Lavdas, Spyros; Driscoll, Jeffrey B.; Jiang, Hongyi; Grote, Richard R.; Osgood, Jr., Richard M.; Panoiu, Nicolae C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/07/2013
Relevância na Pesquisa
26.54%
We study the generation of parabolic self-similar optical pulses in tapered Si photonic nanowires (Si-PhNWs) both at telecom (\lambda=1.55 \mu m) and mid-IR (\lambda=2.2 \mu m) wavelengths. Our computational study is based on a rigorous theoretical model, which fully describes the influence of linear and nonlinear optical effects on pulse propagation in Si-PhNWs with arbitrarily varying width. Numerical simulations demonstrate that, in the normal dispersion regime, optical pulses evolve naturally into parabolic pulses upon propagating in millimeter-long tapered Si-PhNWs, with the efficiency of this pulse reshaping process being strongly dependent on the spectral and pulse parameter regime in which the device operates, as well as the particular shape of the Si-PhNW.; Comment: 4 pages, 5 figures

Evanescent coupling to chalcogenide glass photonic crystal waveguides via tapered microstructured optical fibre nanowires

Grillet, Christian; Moss, David J; Magi, Eric; Freeman, Darren; Madden, Steve; Luther-Davies, Barry; Eggleton, Benjamin J
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Relevância na Pesquisa
26.42%
We demonstrate coupling to chalcogenide glass based photonic crystal waveguides via tapered microstructured fibre nano-wires.