Showing papers on "Nanowire published in 2005"
TL;DR: This work introduces a version of the dye-sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires, which features a surface area up to one-fifth as large as a nanoparticle cell.
Abstract: Excitonic solar cells1—including organic, hybrid organic–inorganic and dye-sensitized cells (DSCs)—are promising devices for inexpensive, large-scale solar energy conversion. The DSC is currently the most efficient2 and stable3 excitonic photocell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light-harvesting molecules. However, nanoparticle DSCs rely on trap-limited diffusion for electron transport, a slow mechanism that can limit device efficiency, especially at longer wavelengths. Here we introduce a version of the dye-sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires. The nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one-fifth as large as a nanoparticle cell. The direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun efficiency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.
5,308 citations
TL;DR: Both the improved crystalline nature of films and increased but controlled demixing between the two constitutes therein after annealing explains the considerable increase of the power conversion efficiency observed in these devices.
Abstract: Transmission electron microscopy and electron diffraction are used to study the changes in morphology of composite films of poly(3-hexylthiophene) (P3HT) and a methanofullerene derivative (PCBM) in bulk heterojunction solar cells. Thermal annealing produces and stabilizes a nanoscale interpenetrating network with crystalline order for both components. P3HT forms long, thin conducting nanowires in a rather homogeneous, nanocrystalline PCBM film. Both the improved crystalline nature of films and increased but controlled demixing between the two constitutes therein after annealing explains the considerable increase of the power conversion efficiency observed in these devices.
1,552 citations
TL;DR: A method for growing vertical ZnO nanowire arrays on arbitrary substrates using either gas-phase or solution-phase approaches is presented and the nanorod arrays made in solution have a rod diameter, length, density, and orientation desirable for use in ordered Nanorod-polymer solar cells.
Abstract: A method for growing vertical ZnO nanowire arrays on arbitrary substrates using either gas-phase or solution-phase approaches is presented. A ∼10 nm-thick layer of textured ZnO nanocrystals with their c axes normal to the substrate is formed by the decomposition of zinc acetate at 200−350 °C to provide nucleation sites for vertical nanowire growth. The nanorod arrays made in solution have a rod diameter, length, density, and orientation desirable for use in ordered nanorod−polymer solar cells.
1,437 citations
TL;DR: Pd-functionalized nanostructures exhibited a dramatic improvement in sensitivity toward oxygen and hydrogen due to the enhanced catalytic dissociation of the molecular adsorbate on the Pd nanoparticle surfaces and the subsequent diffusion of the resultant atomic species to the oxide surface.
Abstract: The sensing ability of individual SnO2 nanowires and nanobelts configured as gas sensors was measured before and after functionalization with Pd catalyst particles. In situ deposition of Pd in the same reaction chamber in which the sensing measurements were carried out ensured that the observed modification in behavior was due to the Pd functionalization rather than the variation in properties from one nanowire to another. Changes in the conductance in the early stages of metal deposition (i.e., before metal percolation) indicated that the Pd nanoparticles on the nanowire surface created Schottky barrier-type junctions resulting in the formation of electron depletion regions within the nanowire, constricting the effective conduction channel and reducing the conductance. Pd-functionalized nanostructures exhibited a dramatic improvement in sensitivity toward oxygen and hydrogen due to the enhanced catalytic dissociation of the molecular adsorbate on the Pd nanoparticle surfaces and the subsequent diffusion ...
1,307 citations
TL;DR: Single-crystal PbSe nanowires are synthesized in solution through oriented attachment of nanocrystal building blocks, resulting in a nearly defect-free crystal lattice and high uniformity of nanowire diameter along the entire length.
Abstract: Single-crystal PbSe nanowires are synthesized in solution through oriented attachment of nanocrystal building blocks. Reaction temperatures of 190-250 degrees C and multicomponent surfactant mixtures result in a nearly defect-free crystal lattice and high uniformity of nanowire diameter along the entire length. The wires' dimensions are tuned by tailoring reaction conditions in a range from approximately 4 to approximately 20 nm in diameter with wire lengths up to approximately 30 microm. PbSe nanocrystals bind to each other on either {100}, {110}, or {111} faces, depending on the surfactant molecules present in the reaction solution. While PbSe nanocrystals have the centrosymmetric rocksalt lattice, they can lack central symmetry due to a noncentrosymmetric arrangement of Pb- and Se-terminated {111} facets and possess dipole driving one-dimensional oriented attachment of nanocrystals to form nanowires. In addition to straight nanowires, zigzag, helical, branched, and tapered nanowires as well as single-crystal nanorings can be controllably prepared in one-pot reactions by careful adjustment of the reaction conditions.
1,164 citations
TL;DR: It is demonstrated that the nonradiating character of the silver nanowires together with minimized damping due to the well developed wire crystal structure allow them to apply as efficient surface plasmon Fabry-Perot resonators.
Abstract: We report on chemically prepared silver nanowires (diameters around 100 nm) sustaining surface plasmon modes with wavelengths shortened to about half the value of the exciting light. As we find by scattered light spectroscopy and near-field optical microscopy, the nonradiating character of these modes together with minimized damping due to the well developed wire crystal structure gives rise to large values of surface plasmon propagation length and nanowire end face reflectivity of about 10 microm and 25%, respectively. We demonstrate that these properties allow us to apply the nanowires as efficient surface plasmon Fabry-Perot resonators.
1,061 citations
TL;DR: In this article, a ZnO nanowire-based dye-sensitized solar cell was proposed to provide a direct conduction path for electrons between the point of photogeneration and the conducting substrate and may offer improved electron transport compared to films of sintered nanoparticles.
Abstract: We describe the design and performance of a ZnO nanowire-based dye-sensitized solar cell. ZnO nanowires with a branched structure were employed as the wide-band-gap semiconductor to construct dye-sensitized solar cells which exhibit energy conversion efficiencies of 0.5% with internal quantum efficiencies of 70%. The nanowires provide a direct conduction path for electrons between the point of photogeneration and the conducting substrate and may offer improved electron transport compared to films of sintered nanoparticles. The devices have light harvesting efficiencies under 10%, indicating that current densities and efficiencies can be improved by an order of magnitude by increasing the nanowire surface area.
1,016 citations
TL;DR: The ability to synthesize rationally III-nitride core/multishell nanowire radial heterostructures opens up significant potential for integrated nanoscale photonic systems, including multicolor lasers.
Abstract: We report the growth and characterization of core/multishell nanowire radial heterostructures, and their implementation as efficient and synthetically tunable multicolor nanophotonic sources. Core/multishell nanowires were prepared by metal-organic chemical vapor deposition with an n-GaN core and InxGa1-xN/GaN/p-AlGaN/p-GaN shells, where variation of indium mole fraction is used to tune emission wavelength. Cross-sectional transmission electron microscopy studies reveal that the core/multishell nanowires are dislocation-free single crystals with a triangular morphology. Energy-dispersive X-ray spectroscopy clearly shows shells with distinct chemical compositions, and quantitatively confirms that the thickness and composition of individual shells can be well controlled during synthesis. Electrical measurements show that the p-AlGaN/p-GaN shell structure yields reproducible hole conduction, and electroluminescence measurements demonstrate that in forward bias the core/multishell nanowires function as light-emitting diodes, with tunable emission from 365 to 600 nm and high quantum efficiencies. The ability to synthesize rationally III-nitride core/multishell nanowire heterostructures opens up significant potential for integrated nanoscale photonic systems, including multicolor lasers.
945 citations
TL;DR: It is found that for Au nanowires, Young's modulus is essentially independent of diameter, whereas the yield strength is largest for the smallest diameter wires, with strengths up to 100 times that of bulk materials, and substantially larger than that reported for bulk nanocrystalline metals.
Abstract: Nanowires have attracted considerable interest as nanoscale interconnects and as the active components of both electronic and electromechanical devices. Nanomechanical measurements are a challenge, but remain key to the development and processing of novel nanowire-based devices. Here, we report a general method to measure the spectrum of nanowire mechanical properties based on nanowire bending under the lateral load from an atomic force microscope tip. We find that for Au nanowires, Young's modulus is essentially independent of diameter, whereas the yield strength is largest for the smallest diameter wires, with strengths up to 100 times that of bulk materials, and substantially larger than that reported for bulk nanocrystalline metals (BNMs)1,2,3,4,5. In contrast to BNMs, nanowire plasticity is characterized by strain-hardening, demonstrating that dislocation motion and pile-up is still operative down to diameters of 40 nm. Possible origins for the different mechanical properties of nanowires and BNMs are discussed.
900 citations
841 citations
TL;DR: By controlling various aspects of nanowire growth, these methods will enable their efficient and economical incorporation into devices to enable their practical integration into devices.
Abstract: Silicon nanowires were synthesized, in a controlled manner, for their practical integration into devices. Gold colloids were used for nanowire synthesis by the vapor−liquid−solid growth mechanism. Using SiCl4 as the precursor gas in a chemical vapor deposition system, nanowire arrays were grown vertically aligned with respect to the substrate. By manipulating the colloid deposition on the substrate, highly controlled growth of aligned silicon nanowires was achieved. Nanowire arrays were synthesized with narrow size distributions dictated by the seeding colloids and with average diameters down to 39 nm. The density of wire growth was successfully varied from ∼0.1−1.8 wires/μm2. Patterned deposition of the colloids led to confinement of the vertical nanowire growth to selected regions. In addition, Si nanowires were grown directly into microchannels to demonstrate the flexibility of the deposition technique. By controlling various aspects of nanowire growth, these methods will enable their efficient and eco...
TL;DR: A dynamic gate effect that seems to involve mobile surface charges and causes hysteresis in the transconductance, among other effects is described.
Abstract: ZnO nanowire field-effect transistors (FETs) were fabricated and studied in vacuum and a variety of ambient gases from 5 to 300 K. In air, these n-type nanowire transistors have among the highest mobilities yet reported for ZnO FETs (Ie ) 13 ( 5c m 2 V -1 s -1 ), with carrier concentrations averaging 5.2 ( 2.5 10 17 cm -3 and on-off current ratios ranging from 10 5 to 10 7 . Four probe measurements show that the resistivity of the Ti/Au-ZnO contacts is 0.002-0.02 ?‚cm. The performance characteristics of the nanowire transistors are intimately tied to the presence and nature of adsorbed surface species. In addition, we describe a dynamic gate effect that seems to involve mobile surface charges and causes hysteresis in the transconductance, among other effects.
TL;DR: Electrical transport in the dark and under ultraviolet (UV) illumination through GaN nanowhiskers grown by molecular beam epitaxy (MBE) is reported, which is sensitively dependent on the column diameter.
Abstract: We report on electrical transport in the dark and under ultraviolet (UV) illumination through GaN nanowhiskers grown by molecular beam epitaxy (MBE), which is sensitively dependent on the column diameter. This new effect is quantitatively described by a size dependent surface recombination mechanism. The essential ingredient for the interpretation of this effect is a diameter dependent recombination barrier, which arises from the interplay between column diameter and space charge layer extension at the column surface.
TL;DR: The galvanic replacement reaction between a Ag template and HAuCl4 in an aqueous solution transforms 30-200 mn Ag nanocubes into Au nanoboxes and nanocages.
Abstract: The galvanic replacement reaction between a Ag template and HAuCl4 in an aqueous solution transforms 30-200 mn Ag nanocubes into Au nanoboxes and nanocages (nanoboxes with porous walls). By controlling the molar ratio of Ag to HAuCl4, the extinction peak of resultant structures can be continuously tuned from the blue (400 nm) to the near-infrared (1200 nm) region of the electromagnetic spectrum. These hollow An nanostructures are characterized by extraordinarily large cross sections for both absorption and scattering. Optical coherence tomography measurements indicate that the 36 nm nanocage has a scattering cross-section of similar to 0.8 X 10(-15) m(2) and an absorption cross-section of similar to 7.3 X 10(-15) m(2). The absorption cross-section is more than five orders of magnitude larger than those of conventional organic dyes. Exposure of Au nanocages to a camera flash resulted in the melting and conversion of Au nanocages into spherical particles due to photothermal heating. Discrete-di poleapproximation calculations suggest that the magnitudes of both scattering and absorption cross-sections of An nanocages can be tailored by controlling their dimensions, as well as the thickness and porosity of their walls. This novel class of hollow nanostructures is expected to find use as both a contrast agent for optical imaging in early stage tumor detection and as a therapeutic agent for photothermal cancer treatment.
TL;DR: The velocity-field characteristic of a domain wall in a nanowire shows two linear regimes, with the wall mobility at high fields reduced tenfold from that at low fields, in accord with theoretical predictions.
Abstract: Ferromagnetic nanowires are likely to play an important role in future spintronic devices. Magnetic domain walls, which separate regions of opposing magnetization in a nanowire, can be manipulated and used to encode information for storage or to perform logic operations. Owing to their reduced size and dimensionality, the characterization of domain-wall motion is an important problem. To compete with other technologies, high-speed operation, and hence fast wall propagation, is essential. However, the domain-wall dynamics in nanowires has only been investigated in the last five years and some results indicate a drastic slowing down of wall motion in higher magnetic fields. Here we show that the velocity-field characteristic of a domain wall in a nanowire shows two linear regimes, with the wall mobility at high fields reduced tenfold from that at low fields. The transition is marked by a region of negative differential mobility and highly irregular wall motion. These results are in accord with theoretical predictions that, above a threshold field, uniform wall movement gives way to turbulent wall motion, leading to a substantial drop in wall mobility. Our results help resolve contradictory reports of wall propagation velocities in laterally confined geometries, and underscore the importance of understanding and enhancing the breakdown field for practical applications.
TL;DR: The growth habits of the nanobelts and nanowires in the two temperature regions indicate the role of growth rate anisotropy and surface energy in dictating the ultimate nanomorphologies.
Abstract: Vertically aligned iron oxide nanobelt and nanowire arrays have been synthesized on a large-area surface by direct thermal oxidation of iron substrates under the flow of O2. The effects of reactive gas pressure, composition, and temperature have been systematically studied. It was found that nanobelts (width, tens of nanometers; thickness, a few nanometers) are produced in the low-temperature region (∼700 °C) whereas cylindrical nanowires tens of nanometers thick are formed at relatively higher temperatures (∼800 °C). Both nanobelts and nanowires are mostly bicrystallites with a length of tens of micrometers which grow uniquely along the [110] direction. The growth habits of the nanobelts and nanowires in the two temperature regions indicate the role of growth rate anisotropy and surface energy in dictating the ultimate nanomorphologies.
TL;DR: The synthesis and transport studies of a 1D hole gas system based on a free-standing germanium/silicon (Ge/Si) core/shell nanowire heterostructure are reported and a "0.7 structure" is observed, suggesting the universality of this phenomenon in interacting 1D systems.
Abstract: Two-dimensional electron and hole gas systems, enabled through band structure design and epitaxial growth on planar substrates, have served as key platforms for fundamental condensed matter research and high-performance devices. The analogous development of one-dimensional (1D) electron or hole gas systems through controlled growth on 1D nanostructure substrates, which could open up opportunities beyond existing carbon nanotube and nanowire systems, has not been realized. Here, we report the synthesis and transport studies of a 1D hole gas system based on a free-standing germanium/silicon (Ge/Si) core/shell nanowire heterostructure. Room temperature electrical transport measurements clearly show hole accumulation in undoped Ge/Si nanowire heterostructures, in contrast to control experiments on single-component nanowires. Low-temperature studies show well-controlled Coulomb blockade oscillations when the Si shell serves as a tunnel barrier to the hole gas in the Ge channel. Transparent contacts to the hole gas also have been reproducibly achieved by thermal annealing. In such devices, we observe conductance quantization at low temperatures, corresponding to ballistic transport through 1D subbands, where the measured subband energy spacings agree with calculations for a cylindrical confinement potential. In addition, we observe a “0.7 structure,” which has been attributed to spontaneous spin polarization, suggesting the universality of this phenomenon in interacting 1D systems. Lastly, the conductance exhibits little temperature dependence, consistent with our calculation of reduced backscattering in this 1D system, and suggests that transport is ballistic even at room temperature.
TL;DR: It is suggested that the interplay of the liquid-solid interfacial energy with the silicon surface energy expressed in terms of an edge tension is responsible for the change of the growth direction.
Abstract: We found that silicon nanowires grown epitaxially on Si (100) via the vapor−liquid−solid growth mechanism change their growth direction from 〈111〉 to 〈110〉 at a crossover diameter of approximately 20 nm. A model is proposed for the explanation of this phenomenon. We suggest that the interplay of the liquid−solid interfacial energy with the silicon surface energy expressed in terms of an edge tension is responsible for the change of the growth direction. The value of the edge tension is estimated by the product of the interfacial thickness with the surface energy of silicon. For large diameters, the direction with the lowest interfacial energy is dominant, whereas for small diameters the surface energy of the silicon nanowire determines the preferential growth direction.
TL;DR: In this paper, an optically pumped room-temperature lasing in GaN nanowires grown by metalorganic chemical vapor deposition (MOCVD) was reported, which achieved a stimulated emission of 22kW∕cm2 that was substantially lower than other previously reported GaN wires.
Abstract: We report optically pumped room-temperature lasing in GaN nanowires grown by metalorganic chemical vapor deposition (MOCVD). Electron microscopy images reveal that the nanowires grow along a nonpolar ⟨11-20⟩ direction, have single-crystal structures and triangular cross sections. The nanowires function as free-standing Fabry–Perot cavities with cavity mode spacings that depend inversely on length. Optical excitation studies demonstrate thresholds for stimulated emission of 22kW∕cm2 that are substantially lower than other previously reported GaN nanowires. Key contributions to low threshold lasing in these MOCVD GaN nanowire cavities and the development of electrically pumped GaN nanowire lasers are discussed.
TL;DR: In this article, ZnO nanowire field effect transistors were implemented as highly sensitive chemical sensors for detection of NO2 and NH3 at room temperature, and a strong negative field was utilized to refresh the sensors by an electrodesorption mechanism.
Abstract: ZnO nanowire field effect transistors were implemented as highly sensitive chemical sensors for detection of NO2 and NH3 at room temperature. Due to a Debye screening length comparable to the nanowire diameter, the electric field applied over the back gate electrode was found to significantly affect the sensitivity as it modulates the carrier concentration. A strong negative field was utilized to refresh the sensors by an electrodesorption mechanism. In addition, different chemisorbed species could be distinguished from the “refresh” threshold voltage and the temporal response of the conductance. These results demonstrated a refreshable field effect sensor with a potential gas identification function.
TL;DR: Nanoscale supercond conductor/semiconductor hybrid devices are assembled from indium arsenide semiconductor nanowires individually contacted by aluminum-based superconductor electrodes, which form superconducting weak links operating as mesoscopic Josephson junctions with electrically tunable coupling.
Abstract: Nanoscale superconductor/semiconductor hybrid devices are assembled from indium arsenide semiconductor nanowires individually contacted by aluminum-based superconductor electrodes. Below 1 kelvin, the high transparency of the contacts gives rise to proximity-induced superconductivity. The nanowires form superconducting weak links operating as mesoscopic Josephson junctions with electrically tunable coupling. The supercurrent can be switched on/off by a gate voltage acting on the electron density in the nanowire. A variation in gate voltage induces universal fluctuations in the normal-state conductance, which are clearly correlated to critical current fluctuations. The alternating-current Josephson effect gives rise to Shapiro steps in the voltage-current characteristic under microwave irradiation.
TL;DR: ZnO nanorod and nanowire films were fabricated on the Si substrates with comb type Pt electrodes by the vapor-phase transport method, and their humidity sensitive characteristics have been investigated.
TL;DR: In this paper, the atmospheric corrosion of silver nanowires and nanoparticles synthesized by the polyol method using poly(vinylpyrrolidone) (PVP) as the capping agent by different techniques, including transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).
Abstract: Metal nanostructures, such as nanoparticles and nanowires, have been proposed as building blocks for several applications in nanofabrication and nanoelectronics However, even when atmospheric corrosion is common in metals, there is a lack of information about the stability of those nanostructures against such phenomenon Therefore, we decided to study the atmospheric corrosion of silver nanowires and nanoparticles synthesized by the polyol method using poly(vinylpyrrolidone) (PVP) as the capping agent by different techniques, including transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) After synthesis and purification, the silver nanostructures were deposited on different substrates and exposed to laboratory air at ambient conditions The structural changes in the samples were monitored by TEM as a function of time for a period of time of 24 weeks Our results demonstrated that these silver nanostructures are susceptible to atmospheric corrosion and that, in most cases, a
TL;DR: In this paper, a variational approach is used to show that nanowire heterostructures are more effective at relieving mismatch strain coherently, in which the mismatch strain is shared by the overlayer and underlayer, and could as well be partially accomodated by the mesh.
Abstract: Due to their unique boundary conditions, nanowire heterostructures may exhibit defect-free interfaces even for systems with large lattice mismatch. Heteroepitaxial material integration is limited by lattice mismatches in planar systems, but we use a variational approach to show that nanowire heterostructures are more effective at relieving mismatch strain coherently. This is an equilibrium model based on the Matthews critical thickness in which the lattice mismatch strain is shared by the nanowire overlayer and underlayer, and could as well be partially accomodated by the
TL;DR: The method offers advantages of direct incorporation of functional biological molecules into the conducting-polymer nanowires during its synthesis, site-specific positioning, built-in electrical contacts, and scalability to high-density nanoarrays over the reported silicon nanowire and carbon nanotube biosensors.
Abstract: A simple, one-step method for fabricating single biologically functionalized conducting-polymer (polypyrrole) nanowire on prepatterned electrodes and its application to biosensing was demonstrated. The biologically functionalized polypyrrole was formed by the electropolymerization of an aqueous solution of pyrrole monomer and the model biomolecule, avidin- or streptavidin-conjugated ZnSe/CdSe quantum dots, within 100 or 200 nm wide by 3 μm long channels between gold electrodes on prefabricated silicon substrate. When challenged with biotin−DNA, the avidin− and streptavidin−polypyrrole nanowires generated a rapid change in resistance to as low as 1 nM, demonstrating the utility of the biomolecule-functionalized nanowire as biosensor. The method offers advantages of direct incorporation of functional biological molecules into the conducting-polymer nanowire during its synthesis, site-specific positioning, built-in electrical contacts, and scalability to high-density nanoarrays over the reported silicon nano...
IBM1
TL;DR: In situ the vapor-liquid-solid (VLS) growth of Si nanowires, in UHV-CVD using Au catalyst, exhibits periodic sawtooth faceting, reflecting an oscillatory growth process, which is interpreted as resulting from the interplay of the geometry and surface energies of the wire and liquid droplet.
Abstract: We observe in situ the vapor-liquid-solid (VLS) growth of Si nanowires, in UHV-CVD using Au catalyst. The nanowire sidewalls exhibit periodic sawtooth faceting, reflecting an oscillatory growth process. We interpret the facet alternation as resulting from the interplay of the geometry and surface energies of the wire and liquid droplet. Such faceting may be present in any VLS growth system in which there are no stable orientations parallel to the growth direction. The sawtooth structure has important implications for electronic mobility and scattering in nanowire devices.
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TL;DR: This procedure, termed on-wire lithography, combines advances in template-directed synthesis of nanowires with electrochemical deposition and wet-chemical etching and allows routine fabrication of face-to-face disk arrays and gap structures in the range of five to several hundred nanometers.
Abstract: We report a high-throughput procedure for lithographically processing one-dimensional nanowires. This procedure, termed on-wire lithography, combines advances in template-directed synthesis of nanowires with electrochemical deposition and wet-chemical etching and allows routine fabrication of face-to-face disk arrays and gap structures in the range of five to several hundred nanometers. We studied the transport properties of 13-nanometer gaps with and without nanoscopic amounts of conducting polymers deposited within by dip-pen nanolithography.
TL;DR: Temperature-dependent and time-resolved PL studies reveal rich spectral features and show that an exciton-exciton interaction is critical to lasing up to 75 K, while an excitation-phonon process dominates at higher temperatures.
Abstract: The mechanism of lasing in single cadmium sulfide (CdS) nanowire cavities was elucidated by temperature-dependent and time-resolved photoluminescence (PL) measurements. Temperature-dependent PL studies reveal rich spectral features and show that an exciton-exciton interaction is critical to lasing up to 75 K, while an exciton-phonon process dominates at higher temperatures. These measurements together with temperature and intensity dependent lifetime and threshold studies show that lasing is due to formation of excitons and, moreover, have implications for the design of efficient, low threshold nanowire lasers.
TL;DR: In this paper, a molecular statics approach based on embedded-atom-method interatomic potentials was employed to study the elasticity of copper nanowires along [001, [110], and [111] crystallographic directions.
Abstract: We employ a molecular statics approach based on embedded-atom-method interatomic potentials to study the elasticity of copper nanowires along [001], [110], and [111] crystallographic directions. Self-consistent comparison with the bulk response clearly shows that the overall nanowire elasticity is primarily due to nonlinear response of the nanowire core. While the surface-stress-induced surface elasticity modifies the behavior for ultrathin nanowires, their contribution is always considerably smaller than that due to nonlinear elasticity of the nanowire core. More importantly, for all three orientations, the surface is softer than an equivalently strained bulk, and the overall nanowire softening or stiffening is determined by orientation-dependent core elasticity.