Search query: radial nanowire rotating

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abstract: Developing efficient charge separation strategies is essential to achieve high power conversion efficiency in fields of chemistry, biology and material science. Herein, we develop a facile strategy for fabrication of unique wafer scale radial nanowire assemblies by exploiting shear force in rotary solution. The assembling mechanism can be well revealed by the large scale stochastic dynamics simulation. Free electrons can be rapidly generated to produce quantitatively tunable current output when the radial nanowire as semblies rotating under the magnetic field. Moreover, the photoconductive performance of the radial semiconductor nanowire assemblies can be remarkably enhanced as the electron hole recombination was retrained by the efficient charge separation under the rotating magnetic field. Such large scale unique nanowire assemblies will facilitate the design of efficient charge separation process in bio system, sensors and photocatalysis.
author_names: Jin-Long Wang

Huijun Jiang

Zhenbei He

Jian-Wei Liu

Rui Wang

Wei-Ran Huang

Lan-Tian Feng

Xiyun Ren

Zhonghuai Hou

Shuhong Yu
title: Radial Nanowire Assemblies under Rotating Magnetic Field Enabled Efficient Charge Separation.
venue: Nano letters
year: 2020

abstract: Nanowires are currently being developed for use in next generation solar cells. In order to produce and improve these solar cells, improved nanowire synthesis methods and non contact measurement techniques are needed. The goal of this project was to design, build, and test a fixture for measuring both axial and radial conductivity of nanowires by terahertz spectroscopy. In order to measure conductivity along both directions, an adjustable rotating fixture for holding nanowire samples was designed and manufactured. The samples prepared for testing consisted of aligned and unaligned zinc oxide nanowires grown on both quartz and silicon substrates.
author_names: Andrew Ling-Ying Belz

Michael E Cournoyer

Anthony Joseph Lawinger
title: Major Qualifying Projects All Years Major Qualifying Projects April 2017 Terahertz Testing Fixture
year: 2019

abstract: We report a comprehensive study of the impact of the structural properties in radial GaAs Al0.3Ga0.7As nanowire quantum well heterostructures on the optical recombination dynamics and electrical transport properties, emphasizing particularly the role of the commonly observed variations of the quantum well thickness at different facets. Typical thickness fluctuations of the radial quantum well observed by transmission electron microscopy lead to pronounced localization. Our optical data exhibit clear spectral shifts and a multipeak structure of the emission for such asymmetric ring structures resulting from spatially separated, yet interconnected quantum well systems. Charge carrier dynamics induced by a surface acoustic wave are resolved and prove efficient carrier exchange on native, subnanosecond time scales within the heterostructure. Experimental findings are corroborated by theoretical modeling, which unambiguously show that electrons and holes localize on facets where the quantum well is the thickest and that even minute deviations of the perfect hexagonal shape strongly perturb the commonly assumed 6 fold symmetric ground state.
author_names: Maximilian M Sonner

Anna Sitek

Lisa Janker

Daniel Rudolph

Daniel Ruhstorfer

Markus Doblinger

Andrei Manolescu

Gerhard Abstreiter

Jonathan J Finley

Achim Wixforth

Gregor Koblmuller

Hubert J Krenner
title: Breakdown of Corner States and Carrier Localization by Monolayer Fluctuations in Radial Nanowire Quantum Wells.
venue: Nano letters
year: 2019

abstract: Abstract It is well known that rotating beams are stretched due to centrifugal forces. Accordingly, it can be speculated that the stretching effect for rotating curved beams leads to changes of the curvature. But this speculation has been not verified and reported in existing literatures. In this paper, a dynamic model of curved beams is derived by using the Absolute Nodal Coordinate Formulation based on radial point interpolation method (ANCF/RPIM) and the transient analysis of curved beams rotating at the steady state angular speed are especially performed by using the ANCF/RPIM. The results show that the curvature of curved beams is reduced due to centrifugal forces. These configuration changes have an important influence on frequency characteristics. Thus, modal analysis should take account of the configuration changes by using steady states which can be obtained in a manner of static analysis. The "static external force" for steady states is a non zero centrifugal force, while centrifugal forces are identically equal to zero in the original ANCF. To this end, this paper uses a floating frame to describe overall rotations of beams, and defines the nodal coordinates located on the floating frame to describe configurations of beam. Based on this description, new ANCF dynamic equations can be easily obtained by using coordinate transformation of the original ANCF dynamic equations, in which the centrifugal forces are not equal to zero. The results show that the configurations in steady and transient states are very close, and transient states are almost located in both sides of the steady state. Therefore, steady states can be regarded approximately as equilibrium positions of vibrational curved beams. By using steady states, the new ANCF dynamic equations can be linearized to determine frequencies of curved beams. Finally, the effects of curvature changes on the frequencies of curved beams, especially "dynamic softening" effect, are investigated, and the reason that these effects are caused in curved beams is explained in detail.
author_names: Yuanzhao Chen

Dingguo Zhang

Liang Li
title: Dynamic analysis of rotating curved beams by using Absolute Nodal Coordinate Formulation based on radial point interpolation method
venue: Journal of Sound and Vibration
year: 2019

abstract: ZnO CuxO core shell radial heterojunction nanowire arrays were fabricated by a straightforward approach which combine two simple, cost effective and large scale preparation methods: (i) thermal oxidation in air of a zinc foil for obtaining ZnO nanowire arrays and (ii) radio frequency magnetron sputtering for covering the surface of the ZnO nanowires with a CuxO thin film. The structural, compositional, morphological and optical properties of the high aspect ratio ZnO CuxO core shell nanowire arrays were investigated. Individual ZnO CuxO core shell nanowires were contacted with Pt electrodes by means of electron beam lithography technique, diode behaviour being demonstrated. Further it was found that these n p radial heterojunction diodes based on single ZnO CuxO nanowires exhibit a change in the current under UV light illumination and therefore behaving as photodetectors.
author_names: Andreea Costas

Camelia Florica

Nicoleta Preda

Nicoleta Georgiana Apostol

Andrei Kuncser

Andrei Nitescu

Ionut Enculescu
title: Radial heterojunction based on single ZnO CuxO core shell nanowire for photodetector applications
venue: Scientific Reports
year: 2019

abstract: Nanowires (NWs) with radial p i n junction have advantages, such as large junction area and small influence from the surface states, which can lead to highly efficient material use and good device quantum efficiency. However, it is difficult to make high quality core shell NW devices, especially single NW devices. Here, the key factors during the growth and fabrication process that influence the quality of single core shell p i n NW devices are studied using GaAs(P) NW photovoltaics as an example. By p doping and annealing, good ohmic contact is achieved on NWs with a diameter as small as 50 60 nm. Single NW photovoltaics are subsequently developed and a record fill factor of 80.5% is shown. These results bring valuable information for making single NW devices, which can further benefit the development of high density integration circuits.
author_names: Yunyan Zhang

Ana M Sanchez

Martin Aagesen

Suguo Huo

H Aruni Fonseka

James A Gott

Dongyoung Kim

Xuezhe Yu

Xingyou Chen

Jia Xu

Tianyi Li

Haotian Zeng

Giorgos Boras

Huiyun Liu
title: Growth and Fabrication of High Quality Single Nanowire Devices with Radial p i n Junctions.
venue: Small
year: 2019

abstract: Semiconductors are essential for modern electronic and optoelectronic devices. To further advance the functionality of such devices, the ability to fabricate increasingly complex semiconductor nanostructures is of utmost importance. Nanowires offer excellent opportunities for new device concepts; heterostructures have been grown in either the radial or axial direction of the core nanowire but never along both directions at the same time. This is a consequence of the common use of a foreign metal seed particle with fixed size for nanowire heterostructure growth. In this work, we present for the first time a growth method to control heterostructure growth in both the axial and the radial directions simultaneously while maintaining an untapered self seeded growth. This is demonstrated for the InAs/InAs1 xPx material system. We show how the dimensions and composition of such axio radial nanowire heterostructures can be designed including the formation of a "pseudo superlattice" consisting of five separate InAs1 xPx segments with varying length. The growth of axio radial nanowire heterostructures offers an exciting platform for novel nanowire structures applicable for fundamental studies as well as nanowire devices. The growth concept for axio radial nanowire heterostructures is expected to be fully compatible with Si substrates.
author_names: Bernhard Mandl

Mario Keplinger

Maria E Messing

Dominik Kriegner

Reine Wallenberg

Lars Samuelson

G Bauer

J Stangl

Vaclav Holy

Knut Deppert
title: Self Seeded Axio Radial InAs InAs1 xPx Nanowire Heterostructures beyond "Common" VLS Growth.
venue: Nano letters
year: 2018

abstract: The electrical and optical properties of low dimensional nanostructures depend critically on size and geometry and may differ distinctly from those of their bulk counterparts. In particular, ultrathin semiconducting layers as well as nanowires have already proven the feasibility to realize and study quantum size effects enabling novel ultrascaled devices. Further, plasmonic metal nanostructures attracted recently a lot of attention because of appealing near field mediated enhancement effects. Thus, combining metal and semiconducting constituents in quasi one dimensional heterostructures will pave the way for ultrascaled systems and high performance devices with exceptional electrical, optical, and plasmonic functionality. This Letter reports on the sophisticated fabrication and structural properties of axial and radial Al Ge and Al Si nanowire heterostructures, synthesized by a thermally induced exchange reaction of single crystalline Ge Si core shell nanowires and Al pads. This enables a self aligned metallic contact formation to Ge segments beyond lithographic limitations as well as ultrathin semiconducting layers wrapped around monocrystalline Al core nanowires. High resolution transmission electron microscopy, energy dispersive X ray spectroscopy, and m Raman measurements proved the composition and perfect crystallinity of these metal semiconductor nanowire heterostructures. This exemplary selective replacement of Ge by Al represents a general approach for the elaboration of radial and axial metal semiconductor heterostructures in various Ge semiconductor heterostructures.
author_names: Masiar Sistani

Minh Anh Luong

Martien I den Hertog

Eric Robin

Maria Spies

Bruno Fernandez

J Yao

Emmerich Bertagnolli

Alois Lugstein
title: Monolithic Axial and Radial Metal Semiconductor Nanowire Heterostructures.
venue: Nano letters
year: 2018

abstract: Nanowires have the potential to play an important role for next generation light emitting diodes. In this work, we present a growth scheme for radial nanowire quantum well structures in the AlGaInP material system using a GaInP nanowire core as a template for radial growth with GaInP as the active layer for emission and AlGaInP as charge carrier barriers. The different layers were analyzed by X ray diffraction to ensure lattice matched radial structures. Furthermore, we evaluated the material composition and heterojunction interface sharpness by scanning transmission electron microscopy energy dispersive X ray spectroscopy. The electro optical properties were investigated by injection luminescence measurements. The presented results can be a valuable track toward radial nanowire light emitting diodes in the AlGaInP material system in the red/orange/yellow color spectrum.
author_names: Alexander H Berg

S Yazdi

Ali Nowzari

Kristian Storm

Vandana Jain

Neimantas Vainorius

Lars Samuelson

Jakob B Wagner

M T Borgstrom
title: Radial Nanowire Light Emitting Diodes in the (AlxGa1 x)yIn1 yP Material System.
venue: Nano letters
year: 2016

abstract: Abstract This paper studies flow and heat transfer of nanofluids over a rotating disk with uniform stretching rate. Three types of nanoparticles Cu, Al2O3 and CuO with water based nanofluids are considered. The governing equations are reduced by Von Karman transformation and then solved by the homotopy analysis method (HAM) which is in close agreement with numerical results. Results indicate that with increasing in stretching strength parameter, the skin friction and the local Nusselt number, the velocity in radial and axial directions increase, whereas the velocity in tangential direction and the thermal boundary layer thickness decrease, respectively. Moreover, the effects of volume fraction and types of nanofluids on velocity and temperature fields are also analyzed.
author_names: Chenguang Yin

Liancun Zheng

Chaoli Zhang

Xinxin Zhang
title: Flow and heat transfer of nanofluids over a rotating disk with uniform stretching rate in the radial direction
year: 2017