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Nano Letters

Dominik Irber, Jakob Seidl, Damon James Carrad, Jonathan Becker, Nari Jeon, Bernhard Loitsch, Julia Winnerl, Sonja Matich, Markus Döblinger, Yang Tang, Stefanie Morkötter, Gerhard Abstreiter, Jonathan J Finley, M Grayson, Lincoln Lauhon, Gregor Koblmueller
Modulation-doped III-V semiconductor nanowire (NW) heterostructures have recently emerged as promising candidates to host high-mobility electron channels for future high-frequency, low-energy transistor technologies. The one-dimensional geometry of NWs also makes them attractive for studying quantum confinement effects. Here, we report correlated investigations into the discrete electronic sub-band structure of confined electrons in the channel of Si delta-doped GaAs/AlAs core-superlattice NW heterostructures and the associated signatures in low-temperature transport...
July 21, 2017: Nano Letters
Jens Kügel, Markus Leisegang, Markus Böhme, Andreas Krönlein, Aimee Sixta, Matthias Bode
Molecular electronics where single molecules perform basic functionalities of digital circuits is a fascinating concept that one day may augment or even replace nowadays semiconductor technologies. The tautomerization of molecules, i.e., the bistable functional position of hydrogen protons within an organic frame, has recently been intensively discussed as a potential avenue towards nano-scale switches. It has been shown that tautomerization can be triggered locally or non-locally, i.e. by a scanning tunneling microscope (STM) tip positioned directly above or in close vicinity to the molecule...
July 21, 2017: Nano Letters
Juan Arturo Alanis, Dhruv Saxena, Sudha Mokkapati, Nian Jiang, Kun Peng, Xiaoyan Tang, Lan Fu, Hark Hoe Tan, Chennupati Jagadish, Patrick Parkinson
Single nanowire lasers based on bottom-up III-V materials have been shown to exhibit room-temperature near-infrared lasing, making them highly promising for use as nanoscale, silicon-integrable and coherent light sources. While lasing behavior is reproducible, small variations in growth conditions across a substrate arising from the use of bottom-up growth techniques can introduce inter-wire disorder, either through geometric or material inhomogeneity. Nanolasers critically depend on both high material quality and tight dimensional tolerances, and as such, lasing threshold is both sensitive to, and a sensitive probe of such inhomogeneity...
July 21, 2017: Nano Letters
Zhihua Zhu, Philip Gareth Evans, Richard F Haglund, Jason Valentine
Mastering dynamic free-space spectral control and modulation in the near-infrared and optical regimes remains a challenging task that is hindered by the available functional materials at high frequencies. Here, we realize an efficient metadevice capable of spectral control by minimizing the thermal mass of a vanadium dioxide phase-change material (PCM) and placing the PCM at the feed gap of a bow-tie field antenna. The device has an experimentally measured tuning range up to 360 nm in the NIR and a modulation depth of 33% at the resonant wavelength...
July 21, 2017: Nano Letters
Liang Zhang, Dan Sun, Jun Feng, Elton J Cairns, Jinghua Guo
Lithium sulfide (Li2S) is a promising cathode material for lithium/sulfur (Li/S) cells due to its high theoretical specific capacity (1166 mAh g(-1)) and capability to pair with non-metallic lithium anodes to avoid potential safety issues. However, when used as the cathode a high charging voltage (~ 4 V vs. Li+/Li) is always necessary to activate Li2S in the first charge process, and the voltage profile becomes similar to that of a common sulfur electrode in the following charge processes. In this report, we have prepared an electrode of nano-sphere Li2S particles and investigated its charging mechanism of the initial two charge processes by in-situ and operando X-ray absorption spectroscopy...
July 21, 2017: Nano Letters
Mary X Wang, Jeffrey D Brodin, Jaime A Millan, Soyoung E Seo, Martin Girard, Monica Olvera de la Cruz, Byeongdu Lee, Chad A Mirkin
Colloidal crystal engineering with DNA can be used to realize precise control over nanoparticle (NP) arrangement. Here, we investigate a case of DNA-based assembly where the properties of DNA as a polyelectrolyte brush are employed to alter a hybridization-driven NP crystallization pathway. Using the coassembly of DNA-conjugated proteins and spherical gold nanoparticles (AuNPs) as a model system, we explore how steric repulsion between noncomplementary, neighboring NPs due to overlapping DNA shells can influence their ligand-directed behavior...
July 21, 2017: Nano Letters
Shunfeng Wang, Junyong Wang, Weijie Zhao, Francesco Giustiniano, Leiqiang Chu, Ivan Verzhbitskiy, Justin Zhou Yong, Goki Eda
We report on efficient carrier-to-exciton conversion and planer electroluminescence from tunnel diodes based on a metal-insulator-semiconductor van der Waals heterostack consisting of few-layer graphene (FLG), hexagonal boron nitride (hBN), and monolayer tungsten disulfide (WS2). These devices exhibit excitonic electroluminescence with extremely low threshold current density of a few pA∙μm-2, which is several orders of magnitude lower compared to the previously reported values for the best planar EL devices...
July 21, 2017: Nano Letters
Yinxiao Li, Mohammad Amin Alibakhshi, Yihong Zhao, Chuanhua Duan
Capillary evaporation in nanoscale conduits is an efficient heat/mass transfer strategy that has been widely utilized by both nature and mankind. Despite its broad impact, the ultimate transport limits of capillary evaporation in nanoscale conduits, governed by the evaporation/condensation kinetics at the liquid-vapor interface, have remained poorly understood. Here we report experimental study of the kinetic limits of water capillary evaporation in two dimensional nanochannels using a novel hybrid channel design...
July 21, 2017: Nano Letters
Peter C Sercel, A Shabaev, Al L Efros
We present a theoretical model for the effect of symmetry breaking introduced by the doping of semiconductor nanocrystals with Coulomb impurities. The presence of a Coulomb center breaks the nanocrystal symmetry and affects its optical properties through the mixing of the hole spin and parity sublevels, breaking the selection rules responsible for the exciton dark state in undoped nanocrystals. After reviewing the effects on the exciton fine structure and optical selection rules using symmetry theory, we present a perturbative model to quantify the effects...
July 21, 2017: Nano Letters
Shiqi Dong, Yongsheng Liu, Ziruo Hong, En-Ping Yao, Pengyu Sun, Lei Meng, Yuze Lin, Jinsong Huang, Gang Li, Yang Yang
We have demonstrated high performance integrated perovskite/bulk-heterojunction (BHJ) solar cells due to the low carrier recombination velocity, high open circuit voltage (Voc) and increased light absorption ability in near-infrared (NIR) region of integrated devices. In particular, we find that the Voc of the integrated devices is dominated by (or pinned to) the perovskite cells, not the OPV cells. A Quasi-Fermi Level Pinning Model was proposed to understand the working mechanism and the origin of the Voc of the integrated perovskite/BHJ solar cell, which following that of the perovskite solar cell and is much higher than that of the low bandgap polymer based organic BHJ solar cell...
July 20, 2017: Nano Letters
Hui Chen, Thomas Pope, Zhuoyan Wu, Dongfei Wang, Lei Tao, De-Liang Bao, Wende Xiao, Jun-Long Zhang, Yu-Yang Zhang, Shi-Xuan Du, Song Gao, Sokrates T Pantelides, Werner A Hofer, Hong-Jun Gao
The quantum efficiency or the rate of conversion of incident photon to free electron in photosynthesis is known to be extremely high. It has long been thought that the origin of this efficiency are molecular vibrations leading to a very fast separation of electrons and holes within the involved molecules. However, molecular vibrations are commonly in the range above 100 meV, which is too high for excitations in an ambient environment. Here, we analyze experimental spectra of single organic molecules on metal surfaces at ~ 4 K, which often exhibit a pronounced dip...
July 20, 2017: Nano Letters
Xi Zhao, Krishna Kanti Dey, Selva Jeganathan, Peter J Butler, Ubaldo M Córdova-Figueroa, Ayusman Sen
Colloidal suspensions containing microscopic swimmers have been the focus of recent studies aimed at understanding the principles of energy transfer in fluidic media at low Reynolds number conditions. Going down in scale, active enzymes have been shown to be force-generating, non-equilibrium systems, thus offering opportunity to examine energy transfer at the ultralow Reynolds number regime. By monitoring the change of diffusion of inert tracers dispersed in active enzyme solutions, we demonstrate that the nature of energy transfer in these systems is similar to that reported for larger microscopic active systems, despite the large differences in scale, modes of energy transduction and propulsion...
July 20, 2017: Nano Letters
Xiang-Tian Kong, Runbo Zhao, Zhiming Wang, Alexander O Govorov
It is very interesting to bring plasmonic circular dichroism spectroscopy to the mid-infrared spectral interval, and there are two reasons for this. This spectral interval is very important for thermal bioimaging, and simultaneously, this spectral range includes vibrational lines of many chiral biomolecules. Here we demonstrate that graphene plasmons indeed offer such opportunity. In particular, we show that chiral graphene assemblies consisting of a few graphene nanodisks can generate strong circular dichroism (CD) in the mid-infrared interval...
July 20, 2017: Nano Letters
Boyang Liu, Kun Fu, Yunhui Gong, Chunpeng Yang, Yonggang Yao, Yanbin Wang, Chengwei Wang, Yudi Kuang, Glenn Pastel, Hua Xie, Eric D Wachsman, Liangbing Hu
High-temperature batteries require the battery components to be thermally stable and function properly at high temperatures. Conventional batteries have high-temperature safety issues such as thermal runaway, which are mainly attributed to the properties of liquid organic electrolytes such as low boiling points and high flammability. In this work, we demonstrate a truly all-solid-state high-temperature battery using a thermally stable garnet solid-state electrolyte, a lithium metal anode, and a V2O5 cathode, which can operate well at 100 °C...
July 20, 2017: Nano Letters
Benjamin L Greenberg, Zachary L Robinson, K V Reich, Claudia Gorynski, Bryan N Voigt, Lorraine F Francis, B I Shklovskii, Eray S Aydil, Uwe R Kortshagen
Networks of ligand-free semiconductor nanocrystals (NCs) offer a valuable combination of high carrier mobility and optoelectronic properties tunable via quantum confinement. In principle, maximizing carrier mobility entails crossing the insulator-metal transition (IMT), where carriers become delocalized. A recent theoretical study predicted that this transition occurs at nρ(3) ≈ 0.3, where n is the carrier density and ρ is the interparticle contact radius. In this work, we satisfy this criterion in networks of plasma-synthesized ZnO NCs by using intense pulsed light (IPL) annealing to tune n and ρ independently...
July 20, 2017: Nano Letters
Byungil Hwang, Wonsik Kim, Jaemin Kim, Subin Lee, Seoyoen Lim, Sangmin Kim, Sang Ho Oh, Seunghwa Ryu, Seung Min Jane Han
Nanoscale metal/graphene nanolayered composite is known to have ultra-high strength as the graphene effectively blocks dislocations from penetrating through the metal/graphene interface. The same graphene interface, which has a strong sp2 bonding, can simultaneously serve as an effective interface for deflecting the fatigue cracks that are generated under cyclic bending cycles. In this study, Cu/Gr composite with repeat layer spacing of 100 nm was tested for bending fatigue at 1.6% and 3.1% strain up to 1,000,000 cycles that showed for the first time a 5-6 times enhancement in fatigue resistance compared to the conventional Cu thin film...
July 19, 2017: Nano Letters
Yiqin Chen, Xiaoyang Duan, Marcus Matuschek, Yanming Zhou, Frank Neubrech, Huigao Duan, Na Liu
High-resolution multicolor printing based on pixelated optical nanostructures is of great importance for promoting advances in color display science. So far, most of the work in this field has been focused on achieving static colors, limiting many potential applications. This inevitably calls for the development of dynamic color displays with advanced and innovative functionalities. In this Letter, we demonstrate a novel dynamic color printing scheme using magnesium-based pixelated Fabry-Pérot cavities by grey-scale nanolithography...
July 19, 2017: Nano Letters
X X Yu, A Gulec, A Yoon, J M Zuo, P W Voorhees, L D Marks
We report direct observation of a "Pac-Man" like coarsening mechanism of a self-supporting thin film of nickel oxide. The ultrathin film has an intrinsic morphological instability due to surface stress leading to the development of local thicker regions at step edges. Density functional theory calculations and continuum modeling of the elastic instability support the model for the process.
July 19, 2017: Nano Letters
Ruiping Zhou, Vaibhav Ostwal, Joerg Appenzeller
The key appeal of two-dimensional (2D) materials such as graphene, transition metal dichalcogenides (TMDs), or phosphorene for electronic applications certainly lies in their atomically thin nature that offers opportunities for devices beyond conventional transistors. It is also this property that makes them naturally suited for a type of integration that is not possible with any three-dimensional (3D) material, that is, forming heterostructures by stacking dissimilar 2D materials together. Recently, a number of research groups have reported on the formation of atomically sharp p/n-junctions in various 2D heterostructures that show strong diode-type rectification...
July 18, 2017: Nano Letters
Jinjin Chen, Jianxun Ding, Weiguo Xu, Tianmeng Sun, Haihua Xiao, Xiuli Zhuang, Xuesi Chen
No abstract text is available yet for this article.
July 18, 2017: Nano Letters
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