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Nano Letters

Dawei Li, Zhiyong Xiao, Sai Mu, Fei Wang, Ying Liu, Jingfeng Song, Xi Huang, Lijia Jiang, Jun Xiao, Lei Liu, Stephen Ducharme, Bai Cui, Xia Hong, Lan Jiang, Jean-Francois Silvain, Yongfeng Lu
Single-crystal transition metal dichalcogenides (TMDs) and TMD-based hetero-junctions have recently attracted significant research and industrial interest owing to their intriguing optical and electrical properties. However, the lack of a simple, low-cost, environmentally friendly, synthetic method and a poor understanding of the growth mechanism post a huge challenge to implementing TMDs in practical applications. In this work, we developed a novel approach for direct formation of high-quality, monolayer and few-layer MoS2 single crystal domains via a single-step rapid thermal processing of a sandwiched reactor with sulfur and molybdenum (Mo) film in a confined reaction space...
January 19, 2018: Nano Letters
Shijiang Luo, Min Song, Xin Li, Yue Zhang, Jeongmin Hong, Xiaofei Yang, Xuecheng Zou, Nuo Xu, Long You
Magnetic skyrmion, a nano-sized spin texture with topological property, has become an area of significant interest due to the scientific insight that it can provide and also its potential impact on applications such as ultra low-energy and ultra high-density logic gates. In the quest for the reconfiguration of single logic device and the implementation of the complete logic functions, a novel reconfigurable skyrmion logic (RSL) is proposed and verified by micromagnetic simulations. Logic functions including AND, OR, NOT, NAND, NOR, XOR, and XNOR are implemented in the ferromagnetic (FM) nanotrack by virtue of various effects including spin orbit torque, skyrmion Hall effect, skyrmion-edge repulsions, and skyrmion-skyrmion collision...
January 19, 2018: Nano Letters
Chihun In, Sangwan Sim, Beom Kim, Hyemin Bae, Hyunseung Jung, Woosun Jang, Myungwoo Son, Jisoo Moon, Maryam Salehi, Seung Young Seo, Aloysius Soon, Moon-Ho Ham, Hojin Lee, Seongshik Oh, Dohun Kim, Moon-Ho Jo, Hyunyong Choi
Understanding the mutual interaction between electronic excitations and lattice vibrations is key for electronic transport and optoelectronic phenomena. Dynamic manipulation of such interaction is elusive as it requires varying the material composition on the atomic level. In turn, recent studies on topological insulators (TIs) have revealed the coexistence of a strong phonon resonance and topologically protected Dirac plasmon, both in the terahertz (THz) frequency range. Here, using these intrinsic characteristics of TIs, we demonstrate a new methodology for controlling electron-phonon interaction by lithographically engineered Dirac surface plasmons in the Bi2Se3 TI...
January 18, 2018: Nano Letters
Megan O Hill, Irene Calvo-Almazan, Mark Allain, Martin Holt, Andrew Ulvestad, Julian Treu, Gregor Koblmueller, Chunyi Huang, Xiaojing Huang, Hanfei Yan, E Nazarestski, Yong S Chu, G Brian Stephenson, Virginie Chamard, Lincoln Lauhon, Stephan O Hruszkewycz
III-As nanowires are candidates for near infrared light emitters and detectors that can be directly integrated onto silicon. However, nanoscale to microscale variations in structure, composition, and strain within a given nanowire, as well as variations between nanowires, pose challenges to correlating microstructure with device performance. In this work, we utilize coherent nano-focused x-rays to characterize stacking defects and strain in a single InGaAs nanowire supported on Si. By reconstructing diffraction patterns from the 2-1-10 Bragg peak, we show that the lattice orientation varies along the length of the wire, while the strain field along the cross-section is largely unaffected, leaving the band structure unperturbed...
January 18, 2018: Nano Letters
David Lynall, Selvakumar V Nair, David Gutstein, Alexander Shik, Igor Savelyev, Marina Blumin, Harry E Ruda
Because of their high aspect ratio, nanostructures are particularly susceptible to effects from surfaces such as slow electron trapping by surface states. However, non-equilibrium trapping dynamics have been largely overlooked when considering transport in nanoelectronic devices. In this study, we demonstrate the profound influence of dynamic trapping processes on transport in InAs nanowires through an investigation of the hysteretic and time-dependent behaviour of the transconductance. We observe large densities (∽1013 cm-2) of slow surface traps and demonstrate the ability to control and permanently fix their occupation and charge through electrostatic manipulation by the gate potential followed by thermal deactivation by cryogenic cooling...
January 18, 2018: Nano Letters
Byeongseop Song, Stephen R Forrest
No abstract text is available yet for this article.
January 18, 2018: Nano Letters
Kiyou Shibata, Toshiaki Tanigaki, Tetsuya Akashi, Hiroyuki Shinada, Ken Harada, Kodai Niitsu, Daisuke Shindo, Naoya Kanazawa, Yoshinori Tokura, Taka-Hisa Arima
To utilize magnetic skyrmions, nano-scale vortex-like magnetic structure, experimental elucidation of their dynamics against current application in various circumstances such as in confined structure and mixture of different magnetic phases is indispensable. Here, we investigate the current-induced dynamics of the coexistence state of magnetic skyrmions and helical magnetic structure in a thin plate of B20-type helimagnet FeGe in terms of in-situ realspace observation using Lorentz transmission electron microscopy (TEM)...
January 18, 2018: Nano Letters
Kai-Chih Huang, Jeremy McCall, Pu Wang, Chien-Sheng Liao, Gregory Eakins, Ji-Xin Cheng, Chen Yang
Graphene grain boundaries (GBs) and other nano-defects can deteriorate electronic properties. Here, using transient absorption (TA) microscopy, we directly visualized GBs by TA intensity increase due to change in density of state. We also observed a faster decay due to defect-accelerated carrier relaxation in the GB area. By line-illumination and parallel detection, we increased the TA intensity imaging speed to 1,000 frames per second, which is 6 orders of magnitude faster than Raman microscopy. Combined with a resonant optical delay tuner which scans a 5...
January 17, 2018: Nano Letters
Xu Zhen, Chen Xie, Yuyan Jiang, Xiangzhao Ai, Bengang Xing, Kanyi Pu
Nanomedicines have shown success in cancer therapy, but the pharmacological actions of most nanomedicine are often nonspecific to cancer cells because of utilization of the therapeutic agents that induce cell apoptosis from inner organelles. We herein report the development of semiconducting photothermal nanoagonists that can remotely and specifically initiate the apoptosis of cancer cells from cell membrane. The organic nanoagonists comprise semiconducting polymer nanoparticles (SPNs) and capsaicin (Cap) as the photothermally-responsive nanocarrier and the agonist for activation of transient receptor potential cation channel subfamily V member 1 (TRPV1), respectively...
January 17, 2018: Nano Letters
Xiaotian Zhang, Tanushree H Choudhury, Mikhail Chubarov, Yu Xiang, Bhakti Jariwala, Fu Zhang, Nasim Alem, Gwo-Ching Wang, Joshua A Robinson, Joan M Redwing
A multi-step diffusion-mediated process was developed to control the nucleation density, size and lateral growth rate of WSe2 domains on c-plane sapphire for the epitaxial growth of large area monolayer films by gas source chemical vapor deposition (CVD). The process consists of an initial nucleation step followed by an annealing period in H2Se to promote surface diffusion of tungsten-containing species to form oriented WSe2 islands with uniform size and controlled density. The growth conditions were then adjusted to suppress further nucleation and laterally grow the WSe2 islands to form a fully coalesced monolayer film in less than one hour...
January 17, 2018: Nano Letters
Jose Navarrete, Chris Siefe, Samuel Alcantar, Michael Belt, Galen D Stucky, Martin Moskovits
Metallic nanostructures exhibit a strong plasmon resonance at a wavelength whose value is sensitive to the charge density in the nanostructure, its size, shape, interparticle coupling and the dielectric properties of its surrounding medium. Here we use UV-Visible transmission and reflectance spectroscopy to track the shifts of the plasmon resonance in an array of gold nanoparticles buried under metal-oxide layers of varying thickness produced using atomic layer deposition (ALD), then coated with bulk layers of one of three metals: aluminum, silver, and gold...
January 17, 2018: Nano Letters
Tao Chen, Baorui Cheng, Guoyin Zhu, Renpeng Chen, Yi Hu, Lianbo Ma, Hongling Lv, Yanrong Wang, Jia Liang, Zuoxiu Tie, Zhong Jin, Jie Liu
No abstract text is available yet for this article.
January 17, 2018: Nano Letters
Wei Luo, Qian Cui, Kai Fang, Ke Chen, Huiru Ma, Jianguo Guan
Microenvironment sensing and imaging are of importance in microscale zones like microreactors, microfluidic systems, and biological cells. But they are so far implemented only based on chemical colors from dyes or quantum dots, which suffered either from photobleaching, quenching, or photoblinking behaviors, or from limited color gamut. In contrast, structural colors from hydrogel-based photonic crystals (PCs) may be stable and tunable in the whole visible spectrum by diffraction peak shift, facilitating the visual detection with high accuracy...
January 17, 2018: Nano Letters
Ioannis Lignos, Loredana Protesescu, Dilara Börte Emiroglu, Richard M Maceiczyk, Simon Schneider, Maksym V Kovalenko, Andrew J deMello
Hybrid organic-inorganic perovskites and in particular formamidinium lead halide (FAPbX3, X = Cl, Br, I) perovskite nanocrystals (NCs) have shown great promise for their implementation in optoelectronic devices. Specifically, the Br and I counterparts have shown unprecedented photoluminescence properties, including precise wavelength tuning (530-790 nm), narrow emission linewidths ( less than 100 meV) and high photoluminescence quantum yields (70-90%). However, the controlled formation of blue emitting FAPb(Cl1-xBrx)3 NCs lags behind their green and red counterparts and the mechanism of their formation remains unclear...
January 16, 2018: Nano Letters
Amaël Obliger, Franz-Josef Ulm, Roland J-M Pellenq
In a context of growing attention for shale gas, the precise impact of organic matter (kerogen) on hydrocarbon recovery from unconventional reservoirs still has to be assessed. Kerogen's microstructure is characterized by a very disordered pore network that greatly affects hydrocarbon transport. The specific structure and texture of this organic matter at the nanoscale is highly dependent on its origin. In this study, by the use of statistical physics and molecular dynamics, we shed some new lights on hydrocarbon transport through realistic molecular models of kerogen at different level of maturity [Bousige et al...
January 16, 2018: Nano Letters
Cynthia Vidal, Dmitry Sivun, Johannes Ziegler, Dong Wang, Peter Schaaf, Calin Hrelescu, Thomas A Klar
An electromagnetic wave impinging on a gold nanosponge coherently excites many electromagnetic hot-spots inside the nanosponge, yielding a polarization dependent scattering spectrum. In contrast, a hole, recombining with an electron, can locally excite plasmonic hot-spots only within a horizon given by the lifetime of localized plasmons and the speed carrying the information that a plasmon has been created. This horizon is about 57 nm, decreasing with increasing size of the nanosponge. Consequently, photoluminescence from large gold nanosponges appears unpolarized...
January 16, 2018: Nano Letters
Young Duck Kim, Yuanda Gao, Ren-Jye Shiue, Lei Wang, Ozgur Burak Aslan, Myung-Ho Bae, Hyungsik Kim, Dongjea Seo, Heon-Jin Choi, Suk Hyun Kim, Andrei Nemilentsau, Tony Low, Cheng Tan, Dmitri K Efetov, Takashi Taniguchi, Kenji Watanabe, Kenneth L Shepard, Tony F Heinz, Dirk Englund, James C Hone
Ultrafast electrically driven nanoscale light sources are critical components in nanophotonics. Compound semiconductor-based light sources for the nanophotonic platforms have been extensively investigated over the past decades. However, monolithic ultrafast light sources with a small footprint remain a challenge. Here, we demonstrate electrically driven ultrafast graphene light emitters that achieve light pulse generation with up to 10 GHz bandwidth, across a broad spectral range from the visible to the near-infrared...
January 16, 2018: Nano Letters
Dongli Wang, Xiaodong Fan, Xiaoguang Li, Siyuan Dai, Laiming Wei, Wei Qin, Fei Wu, Huayang Zhang, Zeming Qi, Changgan Zeng, Zhenyu Zhang, Jian Guo Hou
Quantum mechanical effects of single particles can affect the collective plasmon behaviors substantially. In this work, the quantum control of plasmon excitation and propagation in graphene is demonstrated by adopting the variable quantum transmission of carriers at Heaviside potential steps as a tuning knob. First, the plasmon reflection is revealed to be tunable within a broad range by varying the ratio γ between the carrier energy and potential height, which originates from the quantum mechanical effect of carrier propagation at potential steps...
January 16, 2018: Nano Letters
Sergio Scudino, Daniel Sopu
Due to the fast dynamics of shear band formation and propagation along with the small size and transient character of the shear transformation zones (STZs), the elementary units of plasticity in metallic glasses, the description of the nanoscale mechanism of shear banding often relies on molecular dynamics (MD) simulations. However, the unrealistic parameters used in the simulations related to time constrains may raise questions about whether quantitative comparison between results from experimental and computational analyses is possible...
January 16, 2018: Nano Letters
Marcos H D Guimarães, Gregory Stiehl, David MacNeill, Neal Reynolds, Daniel C Ralph
We present measurements of current-induced spin-orbit torques generated by NbSe2, a fully-metallic transition-metal dichalcogenide material, made using the spin-torque ferromagnetic resonance (ST-FMR) technique with NbSe2/Permalloy bilayers. In addition to the out-of-plane Oersted torque expected from current flow in the metallic NbSe2 layer, we also observe an in-plane antidamping torque with torque conductivity σ ∼ 103 (ħ / 2e) (Ωm)-1 and indications of a weak field-like contribution to the out-of-plane torque oriented opposite to the Oersted torque...
January 12, 2018: Nano Letters
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