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Nano Letters

Damien Salomon, Agnès Messanvi, Joel Eymery, Gema Martínez-Criado
Noncentrosymmetric one dimensional structures are key driving forces behind advanced nanodevices. Owing to the critical role of silane injection in creating nanosized architectures, it has become a challenge to investigate the induced local lattice polarity in single GaN wires. Thus, if axial and radial structures are well-grown by a silane-mediated approach, an ideal model to study their polar orientations is formed. By combining synchrotron X-ray fluorescence and X-ray excited optical luminescence, we show here experimental evidence of the role of silane to promote the N-polarity, light emission and elemental incorporation within single wires...
January 19, 2017: Nano Letters
Yun Chen, Liyi Li, Cheng Zhang, Chia-Chi Tuan, Xin Chen, Jian Gao, Ching-Ping Wong
Kinked silicon (Si) nanowires (NWs) have many special properties that make them attractive for a number of applications, such as microfluidics devices, microelectronic devices, and biosensors. However, fabricating NWs with controlled 3D geometry has been challenging. In this work, a novel method called alternating metal-assisted chemical etching, or alternating MACE, is reported for the fabrication of kinked Si NWs with controlled 3D geometry. By the use of multiple etchants with carefully selected composition, one can control the number of kinks, their locations, and their angles by controlling the number of etchant alternations and the time in each etchant...
January 19, 2017: Nano Letters
Yunlong Zi, Sergey Suslov, Chen Yang
Self-catalyzed growth of III-V nanowires has drawn plenty of attention due to the potentials of integration in current Si-based technologies. The homoparticle-assisted vapor-liquid-solid growth mechanism has been demonstrated for self-catalyzed III-V nanowire growth. However, the understandings of the preferred growth sites of these nanowires are still limited, which obstructs the controlled synthesis and the applications of self-catalyzed nanowire arrays. Here we experimentally demonstrated that thermally created pits could serve as the preferred sites for self-catalyzed InAs nanowire growth...
January 19, 2017: Nano Letters
Ravini U Chandrasena, Weibing Yang, Qingyu Lei, Mario Ulises Delgado-Jaime, Kanishka D Wijesekara, Maryam Golalikhani, Bruce Davidson, Elke Arenholz, Keisuke Kobayashi, Masaaki Kobata, Frank M F de Groot, Ulrich Aschauer, Nicola A Spaldin, Xiaoxing Xi, Alexander X Gray
We demonstrate a novel pathway to control and stabilize oxygen vacancies in complex transition-metal oxide thin films. Using atomic layer-by-layer pulsed laser deposition (PLD) from two separate targets, we synthesize high-quality single-crystalline CaMnO3 films with systematically varying oxygen vacancy defect formation energies as controlled by coherent tensile strain. The systematic increase of the oxygen vacancy content in CaMnO3 as a function of applied in-plane strain is observed and confirmed experimentally using high-resolution soft x-ray absorption spectroscopy (XAS) in conjunction with bulk-sensitive hard x-ray photoemission spectroscopy (HAXPES)...
January 19, 2017: Nano Letters
Hasti Amiri, Kenneth L Shepard, Colin Nuckolls, Raúl Hernández Sánchez
Here we report on the ion conductance through individual, small diameter single-walled carbon nanotubes. We find that they are mimics of ion channels found in natural systems. We explore the factors governing the ion selectivity and permeation through single-walled carbon nanotubes by considering an electrostatic mechanism built around a simplified version of the Gouy-Chapman theory. We find that the single-walled carbon nanotubes preferentially transported cations and that the cation permeability is size-dependent...
January 19, 2017: Nano Letters
Lixia Li, Dong Pan, Yongzhou Xue, Xiaolei Wang, Miaoling Lin, Dan Su, Qinglin Zhang, Xuezhe Yu, Hyok So, Dahai Wei, Baoquan Sun, PingHeng Tan, Anlian Pan, Jianhua Zhao
Here we report on the Ga self-catalyzed growth of near full-composition-range energy-gap-tunable GaAs1-xSbx nanowires by molecular-beam epitaxy. GaAs1-xSbx nanowires with different Sb content are systematically grown by tuning the Sb and As fluxes, and the As background. We find that GaAs1-xSbx nanowires with low Sb content can be grown directly on Si (111) substrates (0 ≤ x ≤ 0.60) and GaAs nanowire stems (0 ≤ x ≤ 0.50) by tuning the Sb and As fluxes. To obtain GaAs1-xSbx nanowires with x ranging from 0...
January 19, 2017: Nano Letters
Rachel H Gilmore, Elizabeth M Y Lee, Mark C Weidman, Adam P Willard, William A Tisdale
Energetic disorder in quantum dot solids adversely impacts charge carrier transport in quantum dot solar cells and electronic devices. Here, we use ultrafast transient absorption spectroscopy to show that homogeneously broadened PbS quantum dot arrays (σhom(2):σinh(2)>19:1, σinh/kBT<0.4) can be realized if quantum dot batches are sufficiently monodisperse (δ ≲ 3.3%). Homogeneous linewidth is found to be an inverse function of quantum dot size, monotonically increasing from ~25 meV for the largest quantum dots (5...
January 19, 2017: Nano Letters
Kai Xu, Dongxue Chen, Fengyou Yang, Zhenxing Wang, Lei Yin, Feng Wang, Ruiqing Cheng, Kaihui Liu, Jie Xiong, Qian Liu, Jun He
Two-dimensional materials (2DMs) are competitive candidates in replacing or supplementing conventional semiconductors owing to their atomically uniform thickness. However, current conventional micro/nanofabrication technologies realize hardly ultrashort channel and integration, especially for sub-10 nm. Meanwhile, experimental device performance associated with the scaling of dimension needs to be investigated, due to the short channel effects. Here, we show a novel and universal technological method to fabricate sub-10 nm gaps with sharp edges and steep sidewalls...
January 19, 2017: Nano Letters
Andrew D La Croix, Andrew O'Hara, Kemar R Reid, Noah J Orfield, Sokrates T Pantelides, Sandra J Rosenthal, Janet E Macdonald
A new ligand that covalently attaches to the surface of colloidal CdSe/CdS nanorods and can simultaneously chelate a molecular metal center is described. The dithiocarbamate-bipyridine ligand system facilitates hole transfer through energetic overlap at the inorganic-organic interface and conjugation through the organic ligand to a chelated metal center. Density functional theory calculations show that the coordination of the free ligand to a CdS surface causes the formation of two hybridized molecular states that lie in the band gap of CdS...
January 19, 2017: Nano Letters
Alessio Andreoni, Su Lin, Haijun Liu, Robert E Blankenship, Hao Yan, Neal W Woodbury
Taking inspiration from photosynthetic mechanisms in natural systems, we introduced a light-sensitive photo protective quenching element to an artificial light-harvesting antenna model to control the flow of energy as a function of light intensity excitation. The orange carotenoid protein (OCP) is a nonphotochemical quencher in cyanobacteria: under high-light conditions, the protein undergoes a spectral shift, and by binding to the phycobilisome, it absorbs excess light and dissipates it as heat. By the use of DNA as a scaffold, an antenna system made of organic dyes (Cy3 and Cy5) was constructed, and OCP was assembled on it as a modulated quenching element...
January 19, 2017: Nano Letters
A M R V L Monteiro, D J Groenendijk, N Manca, E Mulazimoglu, S Goswami, Ya Blanter, L M K Vandersypen, A D Caviglia
Novel physical phenomena arising at the interface of complex oxide heterostructures offer exciting opportunities for the development of future electronic devices. Using the prototypical LaAlO3/SrTiO3 interface as a model system, we employ a single-step lithographic process to realize gate-tunable Josephson junctions through a combination of lateral confinement and local side gating. The action of the side gates is found to be comparable to that of a local back gate, constituting a robust and efficient way to control the properties of the interface at the nanoscale...
January 19, 2017: Nano Letters
Seunghyun Hong, Charlotte Constans, Marcos Vinicius Surmani Martins, Yong Chin Seow, Juan Alfredo Guevara Carrió, Slaven Garaj
Nanostructured graphene-oxide (GO) laminate membranes, exhibiting ultrahigh water flux, are excellent candidates for next generation nanofiltration and desalination membranes, provided the ionic rejection could be further increased without compromising the water flux. Using microscopic drift-diffusion experiments, we demonstrated the ultrahigh charge selectivity for GO membranes, with more than order of magnitude difference in the permeabilities of cationic and anionic species of equivalent hydration radii...
January 19, 2017: Nano Letters
Qinsheng Wang, Cai-Zhen Li, Shaofeng Ge, Jin-Guang Li, Wei Lu, Jiawei Lai, Xuefeng Liu, Junchao Ma, Dapeng Yu, Zhi-Min Liao, Dong Sun
Photodetection with extreme performances in terms of ultrafast response time, broad detection wavelength range, and high sensitivity has wide range of optoelectronic and photonic applications, such as optical communications, interconnects, imaging and remote sensing. Graphene, a typical two-dimensional Dirac semimetal, has shown excellent potential toward high performance photodetector with high operation speed, broadband response and efficient carrier multiplications benefiting from its linear dispersion band structure with high carrier mobility and zero bandgap...
January 18, 2017: Nano Letters
John G Bartholomew, Karmel de Oliveira Lima, Alban Ferrier, Philippe Goldner
We identify the physical mechanisms responsible for the optical homogeneous broadening in Eu(3+):Y2O3 nanoparticles to determine whether rare-earth crystals can be miniaturized to volumes less than λ(3) while preserving their appeal for quantum technology hardware. By studying how the homogeneous line width depends on temperature, applied magnetic field, and measurement time scale, the dominant broadening interactions for various temperature ranges above 3 K were characterized. Below 3 K the homogeneous line width is dominated by an interaction not observed in bulk crystal studies...
January 18, 2017: Nano Letters
Giovanni Ligorio, Marco Vittorio Nardi, Norbert Koch
The scaling of non-volatile memory (NVM) devices based on resistive filament switching to below 100 nm2 footprint area without employing cumbersome lithography is demonstrated. Nanocolumns of the organic semiconductor 4,4-bis[N-(1-naphthyl)-N-phenyl-amino]diphenyl (-NPD) were grown by glancing angle deposition on a silver electrode. Individual NVM devices were electrically characterized by conductive atomic force microscopy with the tip of a conductive cantilever serving as second electrode. The resistive switching mechanism is unambiguously attributed to Ag filament formation between the electrodes...
January 18, 2017: Nano Letters
Fan Zhang, Jiajie Zhu, Daliang Zhang, Udo Schwingenschlögl, Husam N Alshareef
We have systematically changed the number of atomic layers stacked in 2D SnO nanosheet anodes and studied their Sodium Ion Battery (SIB) performance. The results indicate that as the number of atomic SnO layers in a sheet decreases, both the capacity and cycling stability of the Na ion battery improve. The thinnest SnO nanosheet anodes (2-6 SnO monolayers) exhibited the best performance. Specifically, an initial discharge and charge capacity of 1072 and 848 mAh g-1 were observed, respectively, at 0.1 A g-1...
January 18, 2017: Nano Letters
Li Huang, Yanfang Zhang, Yu-Yang Zhang, Wenyan Xu, Yande Que, En Li, Jinbo Pan, Yeliang Wang, Yunqi Liu, Shixuan Du, Sokrates T Pantelides, Hong-Jun Gao
Silicon-based two-dimensional (2D) materials are uniquely suited for integration in Si-based electronics. Silicene, an analog of graphene, was recently fabricated on several substrates and was used to make a field-effect transistor. Here, we report that, when Ru(0001) is used as a substrate, a range of distinct monolayer silicon structures forms, evolving towards silicene with increasing Si coverage. Low Si coverage produces a herringbone structure, a hitherto undiscovered 2D phase of silicon. With increasing Si coverage, herringbone elbows evolve into silicene-like honeycomb stripes under tension, resulting in a herringbone-honeycomb 2D superlattice...
January 18, 2017: Nano Letters
Paul Seifert, Kristina Vaklinova, Klaus Kern, Marko Burghard, Alexander Holleitner
Topological insulators constitute a fascinating class of quantum materials with nontrivial, gapless states on the surface and insulating bulk states. By revealing the optoelectronic dynamics in the whole range from femto- to microseconds, we demonstrate that the long surface lifetime of Bi2Te2Se nanowires allows us to access the surface states by a pulsed photoconduction scheme and that there is a prevailing bolometric response of the surface states. The interplay of the surface and bulk states dynamics on the different time scales gives rise to a surprising physical property of Bi2Te2Se nanowires: their pulsed photoconductance changes polarity as a function of laser power...
January 18, 2017: Nano Letters
S M Sadaf, S Zhao, Y Wu, Y-H Ra, X Liu, S Vanka, Z Mi
To date, semiconductor light emitting diodes (LEDs) operating in the deep ultraviolet (UV) spectral range exhibit very low efficiency due to the presence of large densities of defects and extremely inefficient p-type conduction of conventional AlGaN quantum well heterostructures. We have demonstrated that such critical issues can be potentially addressed by using nearly defect-free AlGaN tunnel junction core-shell nanowire heterostructures. The core-shell nanowire arrays exhibit high photoluminescence efficiency (∼80%) in the UV-C band at room temperature...
January 18, 2017: Nano Letters
Andrea Vezzoli, Richard J Brooke, Nicolò Ferri, Simon J Higgins, Walther Schwarzacher, Richard J Nichols
In most single- or few-molecule devices, the contact electrodes are simple ohmic resistors. Here we describe a new type of single-molecule device in which metal and semiconductor contact electrodes impart a function, namely, current rectification, which is then modified by a molecule bridging the gap. We study junctions with the structure Au STM tip/X/n-GaAs substrate, where "X" is either a simple alkanedithiol or a conjugated unit bearing thiol/methylthiol contacts, and we detect current jumps corresponding to the attachment and detachment of single molecules...
January 18, 2017: Nano Letters
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