The Experts below are selected from a list of 252258 Experts worldwide ranked by ideXlab platform
Hannah J Joyce - One of the best experts on this subject based on the ideXlab platform.
-
a review of the electrical properties of semiconductor Nanowires insights gained from terahertz conductivity spectroscopy
Semiconductor Science and Technology, 2016Co-Authors: Hannah J Joyce, Jessica L. Boland, Chris Davies, Sarwat A Baig, Michael B JohnstonAbstract:© 2016 IOP Publishing Ltd. Accurately measuring and controlling the electrical properties of semiconductor Nanowires is of paramount importance in the development of novel Nanowire-based devices. In light of this, terahertz (THz) conductivity spectroscopy has emerged as an ideal non-contact technique for probing Nanowire electrical conductivity and is showing tremendous value in the targeted development of Nanowire devices. THz spectroscopic measurements of Nanowires enable charge carrier lifetimes, mobilities, dopant concentrations and surface recombination velocities to be measured with high accuracy and high throughput in a contact-free fashion. This review spans seminal and recent studies of the electronic properties of Nanowires using THz spectroscopy. A didactic description of THz time-domain spectroscopy, optical pump-THz probe spectroscopy, and their application to Nanowires is included. We review a variety of technologically important Nanowire materials, including GaAs, InAs, InP, GaN and InN Nanowires, Si and Ge Nanowires, ZnO Nanowires, Nanowire heterostructures, doped Nanowires and modulation-doped Nanowires. Finally, we discuss how THz measurements are guiding the development of Nanowire-based devices, with the example of single-Nanowire photoconductive THz receivers.
-
Increased Photoconductivity Lifetime in GaAs Nanowires by Controlled n-Type and p-Type Doping
ACS Nano, 2016Co-Authors: Jessica L. Boland, Alberto Casadei, Gözde Tütüncüoglu, Federico Matteini, F. Jabeen, Anna Fontcuberta I Morral, Hannah J Joyce, Laura M Herz, Chris Davies, Michael B JohnstonAbstract:Controlled doping of GaAs Nanowires is crucial for the development of Nanowire-based electronic and optoelectronic devices. Here, we present a noncontact method based on time-resolved terahertz photoconductivity for assessing n- and p-type doping efficiency in Nanowires. Using this technique, we measure extrinsic electron and hole concentrations in excess of 1018 cm–3 for GaAs Nanowires with n-type and p-type doped shells. Furthermore, we show that controlled doping can significantly increase the photoconductivity lifetime of GaAs Nanowires by over an order of magnitude: from 0.13 ns in undoped Nanowires to 3.8 and 2.5 ns in n-doped and p-doped Nanowires, respectively. Thus, controlled doping can be used to reduce the effects of parasitic surface recombination in optoelectronic Nanowire devices, which is promising for Nanowire devices, such as solar cells and Nanowire lasers.
-
ultralow surface recombination velocity in inp Nanowires probed by terahertz spectroscopy
Nano Letters, 2012Co-Authors: Hannah J Joyce, Qiang Gao, C Jagadish, Hark Hoe Tan, J Wongleung, Chaw Keong Yong, Callum J Docherty, Suriati Paiman, J Lloydhughes, Laura M HerzAbstract:Using transient terahertz photoconductivity measurements, we have made noncontact, room temperature measurements of the ultrafast charge carrier dynamics in InP Nanowires. InP Nanowires exhibited a very long photoconductivity lifetime of over 1 ns, and carrier lifetimes were remarkably insensitive to surface states despite the large Nanowire surface area-to-volume ratio. An exceptionally low surface recombination velocity (170 cm/s) was recorded at room temperature. These results suggest that InP Nanowires are prime candidates for optoelectronic devices, particularly photovoltaic devices, without the need for surface passivation. We found that the carrier mobility is not limited by Nanowire diameter but is strongly limited by the presence of planar crystallographic defects such as stacking faults in these predominantly wurtzite Nanowires. These findings show the great potential of very narrow InP Nanowires for electronic devices but indicate that improvements in the crystallographic uniformity of InP Nanowires will be critical for future Nanowire device engineering.
-
phase perfection in zinc blende and wurtzite iii v Nanowires using basic growth parameters
Nano Letters, 2010Co-Authors: Hannah J Joyce, Qiang Gao, Hark Hoe Tan, J Wongleung, C JagadishAbstract:Controlling the crystallographic phase purity of III-V Nanowires is notoriously difficult, yet this is essential for future Nanowire devices. Reported methods for controlling Nanowire phase require dopant addition, or a restricted choice of Nanowire diameter, and only rarely yield a pure phase. Here we demonstrate that phase-perfect Nanowires, of arbitrary diameter, can be achieved simply by tailoring basic growth parameters: temperature and V/III ratio. Phase purity is achieved without sacrificing important specifications of diameter and dopant levels. Pure zinc blende Nanowires, free of twin defects, were achieved using a low growth temperature coupled with a high V/III ratio. Conversely, a high growth temperature coupled with a low V/III ratio produced pure wurtzite Nanowires free of stacking faults. We present a comprehensive nucleation model to explain the formation of these markedly different crystal phases under these growth conditions. Critical to achieving phase purity are changes in surface energy of the Nanowire side facets, which in turn are controlled by the basic growth parameters of temperature and V/III ratio. This ability to tune crystal structure between twin-free zinc blende and stacking-fault-free wurtzite not only will enhance the performance of Nanowire devices but also opens new possibilities for engineering Nanowire devices, without restrictions on Nanowire diameters or doping.
-
novel growth phenomena observed in axial inas gaas Nanowire heterostructures
Small, 2007Co-Authors: Mohanchand Paladugu, G.j. Auchterlonie, Hannah J Joyce, Chennupati JagadishAbstract:Growth behavior in Axial InAs/GaAs Nanowire heterostructures was observed as they have important applications in optoelectronics. The physical phenomena, which resulted in the failure of axial InAs Nanowire growth on GaAs Nanowires, was demonstrated. The vapor-liquid-solid (VPS) method was used for the growth of Nanowire heterostructures. The changes in the growth directions of Nanowires were studied by Transmission electron microscopy (TEM), which lead to the growth failure of InAs Axial growth on the GaAs Nanowires. The catalyst used for the growth of the InAs/GaAs Nanowires was gold. TEM investigations have determined that the initial InAs clustering at the edge of an Au/GaAs interface results in Au particles that are unbalanced with the GaAs surface and wetting between the Au and the GaAs Nanowire sidewalls results in the downward growth of InAs, in which InAs Nanowire sections have an epitaxial relationship with GaAs sections.
Benjamin J Wiley - One of the best experts on this subject based on the ideXlab platform.
-
The resistance of Cu Nanowire–Nanowire junctions and electro-optical modeling of Cu Nanowire networks
Applied Physics Letters, 2020Co-Authors: Hugh G. Manning, Benjamin J Wiley, Patrick F. Flowers, Mutya A. Cruz, Claudia Gomes Da Rocha, Colin O' Callaghan, Mauro S. Ferreira, John J. BolandAbstract:Flexible transparent conductors made from networks of metallic Nanowires are a potential replacement for conventional, non-flexible, and transparent conducting materials such as indium tin oxide. Cu Nanowires are particularly interesting as cost-effective alternatives to Ag Nanowires—the most investigated metallic Nanowire to date. To optimize the conductivity of Cu Nanowire networks, the resistance contributions from the material and Nanowire junctions must be independently known. In this paper, we report the resistivity values (ρ) of individual solution-grown Cu Nanowires ⟨ρ⟩ = 20.1 ± 1.3 nΩ m and the junction resistance (Rjxn) between two overlapping Cu Nanowires ⟨Rjxn⟩ = 205.7 ± 57.7 Ω. These electrical data are incorporated into an electro-optical model that generates analogs for Cu Nanowire networks, which accurately predict without the use of fitting factors the optical transmittance and sheet resistance of the transparent electrode. The model's predictions are validated using experimental data from the literature of Cu Nanowire networks composed of a wide range of aspect ratios (Nanowire length/diameter). The separation of the material resistance and the junction resistance allows the effectiveness of post-deposition processing methods to be evaluated, aiding research and industry groups in adopting a materials-by-design approach.
-
copper Nanowire networks with transparent oxide shells that prevent oxidation without reducing transmittance
ACS Nano, 2014Co-Authors: Zuofeng Chen, Ian E Stewart, Benjamin J WileyAbstract:Transparent conducting films of solution-synthesized copper Nanowires are an attractive alternative to indium tin oxide due to the relative abundance of Cu and the low cost of solution-phase Nanowire coating processes. However, there has to date been no way to protect Cu Nanowires with a solution-phase process that does not adversely affect the optoelectric performance of Cu Nanowire films. This article reports that the electrodeposition of zinc, tin, or indium shells onto Cu Nanowires, followed by oxidation of these shells, enables the protection of Cu Nanowire films against oxidation without decreasing film performance.
-
integrating simulations and experiments to predict sheet resistance and optical transmittance in Nanowire films for transparent conductors
ACS Nano, 2013Co-Authors: Rose M Mutiso, Aaron R Rathmell, Benjamin J Wiley, Michelle C Sherrott, Karen I WineyAbstract:Metal Nanowire films are among the most promising alternatives for next-generation flexible, solution-processed transparent conductors. Breakthroughs in Nanowire synthesis and processing have reported low sheet resistance (Rs ≤ 100 Ω/sq) and high optical transparency (%T > 90%). Comparing the merits of the various Nanowires and fabrication methods is inexact, because Rs and %T depend on a variety of independent parameters including Nanowire length, Nanowire diameter, areal density of the Nanowires and contact resistance between Nanowires. In an effort to account for these fundamental parameters of Nanowire thin films, this paper integrates simulations and experimental results to build a quantitatively predictive model. First, by fitting the results from simulations of quasi-2D rod networks to experimental data from well-defined Nanowire films, we obtain an effective average contact resistance, which is indicative of the Nanowire chemistry and processing methods. Second, this effective contact resistance i...
-
the effect of Nanowire length and diameter on the properties of transparent conducting Nanowire films
Nanoscale, 2012Co-Authors: Stephen M Bergin, Patrick Charbonneau, Aaron R Rathmell, Yuhui Chen, Zhiyuan Li, Benjamin J WileyAbstract:This article describes how the dimensions of Nanowires affect the transmittance and sheet resistance of a random Nanowire network. Silver Nanowires with independently controlled lengths and diameters were synthesized with a gram-scale polyol synthesis by controlling the reaction temperature and time. Characterization of films composed of Nanowires of different lengths but the same diameter enabled the quantification of the effect of length on the conductance and transmittance of silver Nanowire films. Finite-difference time-domain calculations were used to determine the effect of Nanowire diameter, overlap, and hole size on the transmittance of a Nanowire network. For individual Nanowires with diameters greater than 50 nm, increasing diameter increases the electrical conductance to optical extinction ratio, but the opposite is true for Nanowires with diameters less than this size. Calculations and experimental data show that for a random network of Nanowires, decreasing Nanowire diameter increases the number density of Nanowires at a given transmittance, leading to improved connectivity and conductivity at high transmittance (>90%). This information will facilitate the design of transparent, conducting Nanowire films for flexible displays, organic light emitting diodes and thin-film solar cells.
Yu Huang - One of the best experts on this subject based on the ideXlab platform.
-
Silicon and Silicide Nanowires: Applications, Fabrication, and Properties - Silicon and silicide Nanowires : applications, fabrication, and properties
2016Co-Authors: Yu HuangAbstract:In Situ Observations of Vapor-Liquid-Solid Growth of Silicon Nanowires, S. Kodambaka Introduction Experimental 4 Silicon Nanowire Nucleation Kinetics Silicon Nanowire Growth Kinetics Summary and Outlook Growth of Germanium, Silicon, and Ge-Si Heterostructured Nanowires, Shadi A. Dayeh and S. Thomas Picraux Introduction 23 The VLS Growth Mechanism Size Effects in Nanowire Growth Temperature Effects on Nanowire Growth Pressure Effects on Nanowire Growth Dopant Precursor Influence on Nanowire Growth Defects during VLS Growth of Semiconductor Nanowires Ge Core/Si Shell Heterostructured Nanowires Unique Opportunities for Bandgap Engineering in Semiconductor Nanowires Conclusions Transition Metal Silicide Nanowires: Synthetic Methods and Applications, Jeremy M. Higgins, Andrew L. Schmitt, and Song Jin Introduction Formation of Bulk and Thin-Film Metal Silicides in Diffusion Couples Silicide Nanowire Growth Techniques Conclusion Metal Silicide Nanowires: Growth and Properties, L. J. Chen and W. W. Wu Introduction Epitaxial Growth of Silicide Nanowires on Si Substrate Growth of Free-Standing Silicide Nanowires and Their Properties Formation of Silicide/Si/Silicide Nano-Heterostructures from Si Nanowires Conclusions Formation of Epitaxial Silicide in Silicon Nanowires, Yi-Chia Chou, Kuo-Chang Lu, and King-Ning Tu Introduction Introduction to Solid-State Phase Transformation in Thin Film Nanoscale Silicide Formation by Point Contact Reaction between Ni/Co and Si Nanowires Homogeneous Nucleation of Nanoscale Silicide Formation Conclusion Interaction between Inverse Kirkendall Effect and Kirkendall Effect in Nanoshells and Nanowires, A. M. Gusak and T. V. Zaporozhets Introduction Basic Notions Instability of Hollow Nanostructures Formation of Hollow Shells Cross-Over from Formation to Collapse Electrical Transport Properties of Doped Silicon Nanowires, Aya Seike and Iwao Ohdomari Introduction Fabrication Processes and Electrical Measurements Introduction of Strain into Nanowire Channels by Oxidation, and Evaluation of Stress within Individual Nanowires Electrical Characterization of Nanowire FETs Summary Silicon Nanowires and Related Nanostructures as Lithium-Ion Battery Anodes, Liangbing Hu, Lifeng Cui, Seung Sae Hong, James McDonough, and Yi Cui Lithium-Ion Batteries and Different Types of Anodes Advantages and Challenges of Silicon Anodes Thin Film Silicon Anodes and Microsized Particles Vapor-Liquid-Solid (VLS)-Grown SiNWs as High-Capacity Anode Surface Characterization and Electrochemical Analysis of the Solid-Electrolyte Interphase (SEI) on Silicon Nanowires Si Core-Shell Structures for Anodes Other Si Nanostructures Solution-Processed Si Nanostructures Some Fundamental Aspects Remaining Challenges and Commercialization Porous Silicon Nanowires, Yongquan Qu and Xiangfeng Duan Introduction Synthesis of Porous Silicon Nanowires Properties of Porous Silicon Nanowire Applications of Porous Silicon Nanowire Conclusion Nanoscale Contact Engineering for Si Nanowire Devices, Yung-Chen Lin and Yu Huang Scope of the Chapter Introduction Synthetic Approaches to Nanoscale Silicides Contact Formation through Solid-State Reaction Silicide Growth Mechanism New Technical Approaches or Structures for Low-Contact Resistance FET and Short-Channel Device Electronic Properties of Silicide NWs and Silicide/Si/Silicide Heterostructures Conclusion Index
-
Single crystalline PtSi Nanowires, PtSi/Si/PtSi Nanowire heterostructures, and nanodevices.
Nano letters, 2008Co-Authors: Yung-chen Lin, Jingwei Bai, Lih J. Chen, Yu HuangAbstract:We report the formation of PtSi Nanowires, PtSi/Si/PtSi Nanowire heterostructures, and nanodevices from such heterostructures. Scanning electron microscopy studies show that silicon Nanowires can be converted into PtSi Nanowires through controlled reactions between lithographically defined platinum pads and silicon Nanowires. High-resolution transmission electron microscopy studies show that PtSi/Si/PtSi heteorstructure has an atomically sharp interface with epitaxial relationships of Si[110]//PtSi[010] and Si(111)//PtSi(101). Electrical measurements show that the pure PtSi Nanowires have low resistivities ∼28.6 μΩ·cm and high breakdown current densities >1 × 108 A/cm2. Furthermore, using single crystal PtSi/Si/PtSi Nanowire heterostructures with atomically sharp interfaces, we have fabricated high-performance nanoscale field-effect transistors from intrinsic silicon Nanowires, in which the source and drain contacts are defined by the metallic PtSi Nanowire regions, and the gate length is defined by the ...
Michael B Johnston - One of the best experts on this subject based on the ideXlab platform.
-
a review of the electrical properties of semiconductor Nanowires insights gained from terahertz conductivity spectroscopy
Semiconductor Science and Technology, 2016Co-Authors: Hannah J Joyce, Jessica L. Boland, Chris Davies, Sarwat A Baig, Michael B JohnstonAbstract:© 2016 IOP Publishing Ltd. Accurately measuring and controlling the electrical properties of semiconductor Nanowires is of paramount importance in the development of novel Nanowire-based devices. In light of this, terahertz (THz) conductivity spectroscopy has emerged as an ideal non-contact technique for probing Nanowire electrical conductivity and is showing tremendous value in the targeted development of Nanowire devices. THz spectroscopic measurements of Nanowires enable charge carrier lifetimes, mobilities, dopant concentrations and surface recombination velocities to be measured with high accuracy and high throughput in a contact-free fashion. This review spans seminal and recent studies of the electronic properties of Nanowires using THz spectroscopy. A didactic description of THz time-domain spectroscopy, optical pump-THz probe spectroscopy, and their application to Nanowires is included. We review a variety of technologically important Nanowire materials, including GaAs, InAs, InP, GaN and InN Nanowires, Si and Ge Nanowires, ZnO Nanowires, Nanowire heterostructures, doped Nanowires and modulation-doped Nanowires. Finally, we discuss how THz measurements are guiding the development of Nanowire-based devices, with the example of single-Nanowire photoconductive THz receivers.
-
Increased Photoconductivity Lifetime in GaAs Nanowires by Controlled n-Type and p-Type Doping
ACS Nano, 2016Co-Authors: Jessica L. Boland, Alberto Casadei, Gözde Tütüncüoglu, Federico Matteini, F. Jabeen, Anna Fontcuberta I Morral, Hannah J Joyce, Laura M Herz, Chris Davies, Michael B JohnstonAbstract:Controlled doping of GaAs Nanowires is crucial for the development of Nanowire-based electronic and optoelectronic devices. Here, we present a noncontact method based on time-resolved terahertz photoconductivity for assessing n- and p-type doping efficiency in Nanowires. Using this technique, we measure extrinsic electron and hole concentrations in excess of 1018 cm–3 for GaAs Nanowires with n-type and p-type doped shells. Furthermore, we show that controlled doping can significantly increase the photoconductivity lifetime of GaAs Nanowires by over an order of magnitude: from 0.13 ns in undoped Nanowires to 3.8 and 2.5 ns in n-doped and p-doped Nanowires, respectively. Thus, controlled doping can be used to reduce the effects of parasitic surface recombination in optoelectronic Nanowire devices, which is promising for Nanowire devices, such as solar cells and Nanowire lasers.
Eric N. Dattoli - One of the best experts on this subject based on the ideXlab platform.
-
Branched SnO2 Nanowires on metallic Nanowire backbones for ethanol sensors application
Applied Physics Letters, 2008Co-Authors: Qing Wan, Jin Huang, Zhong Xie, Taihong Wang, Eric N. DattoliAbstract:We report the synthesis of hierarchically branched semiconducting SnO2 Nanowire on metallic Sb-doped SnO2 Nanowires by the sequential seeding of multiple Nanowire generations with Au nanoparticles as catalysts. Such semiconducting Nanowire/metallic backbone complex structures increase the potential functionality of SnO2 Nanowires. Branched SnO2 Nanowire films are used as sensing materials for high-performance ethanol sensor fabrication. The Nanowire sensors show sub-ppm sensitivity and fast response and recovery times at 300°C. A linear equation relationship between sensitivity and the ethanol vapor concentration was observed.
