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Nano Letters

Wei Ting Chen, Alexander Yutong Zhu, Jared Sisler, Yao-Wei Huang, Kerolos Yousef, Eric Lee, Chengwei Qiu, Federico Capasso
Existing methods to correct for chromatic aberrations in optical systems are limited to two approaches: varying the material dispersion in refractive lenses, or incorporating grating dispersion via diffractive optical elements. Recently, single-layer broadband achromatic metasurface lenses have been demonstrated but are limited to diameters of the order of 100 microns due to the required large group delays. Here, we circumvent this limitation and design a metacorrector by an approach combining tunable phase and artificial dispersion to correct spherical and chromatic aberrations in a large spherical plano-convex lens...
November 13, 2018: Nano Letters
Ya-Lun Ho, J Kenji Clark, Kamal Syazwan, Jean-Jacques Delaunay
Plasmonic-waveguide lasers, which exhibit sub-diffraction limit lasing and light propagation, are promising for the next-generation of nanophotonic devices in computation, communication, and biosensing. Plasmonic lasers supporting waveguide modes are often based on nanowires grown with bottom-up techniques that need to be transferred and aligned for use in optical circuits. Here, we demonstrate a monolithically fabricated ZnO/Al plasmonic-waveguide nanolaser compatible with the fabrication requirements of on-chip circuits...
November 13, 2018: Nano Letters
Emiel W A Visser, Matěj Horáček, Peter Zijlstra
Biopolymers such as DNA, RNA and proteins exploit conformational changes to modulate their function. Although state-of-the-art single-molecule approaches enable identification of conformational states, the transition path and metastable intermediates often remain elusive because they occur on microsecond timescales. Here we introduce a method to probe conformational dynamics with microsecond integration times based on a heterodimer of plasmonic particles. By combining Brownian dynamics and electromagnetic simulations we find that integration times of 1 µs can be routinely achieved, providing the capability to identify short-lived intermediates and transition paths at the single-molecule level in real-time...
November 13, 2018: Nano Letters
Robert Czaplicki, Antti Kiviniemi, Mikko Johannes Huttunen, Xiaorun Zang, Timo Stolt, Ismo Vartiainen, Jérémy Butet, Markku Kuittinen, Olivier J F Martin, Martti Kauranen
We investigate optical second-harmonic generation (SHG) from metasurfaces where noncentrosymmetric V-shaped gold nanoparticles are ordered into regular array configurations. In contrast to expectations, a substantial enhancement of the SHG signal is observed when the number density of the particles in the array is reduced. More specifically, by halving the number density, we obtain over five-fold enhancement in SHG intensity. This striking result is attributed to favorable interparticle interactions mediated by the lattice, where surface-lattice resonances lead to spectral narrowing of the plasmon resonances...
November 13, 2018: Nano Letters
Suo Wang, Huazhou Chen, Ren-Min Ma
Plasmonic nanolasers break the diffraction limit for an optical oscillator, which brings new capabilities for various applications, ranging from on-chip optical interconnector to biomedical sensing and imaging. However, the inevitably accompanied metallic absorption loss could convert the input power to heat rather than radiations leading to undesired low external quantum efficiency and device degradation. To date, direct characterization of quantum efficiency of plasmonic nanolasers is still a forbidden task due to its near-field surface plasmon emissions, divergent emission profile and the limited emission power...
November 13, 2018: Nano Letters
Chuanzhe Meng, Nitin Muralidharan, Eti Teblum, Kathleen Moyer, Gilbert Nessim, Cary L Pint
Here we demonstrate a composite material exhibiting dual multifunctional properties of a structural material and a redox-active battery. This incorporates three-dimensional aligned carbon nanotube interfaces that weave together a structural frame, redox-active battery materials, and a Kevlar-infiltrated solid electrolyte that facilitates ion transfer. Relative to the total measured composite material mass, we demonstrate energy density up to ~ 1.4 Wh/kg, elastic modulus of 7 GPa, and tensile strength exceeding 0...
November 13, 2018: Nano Letters
Hyomin Lee, Jihye Choi, Euihwan Jeong, Seongho Baek, Hee Chan Kim, Jong-Hee Chae, Youngil Koh, Sang Woo Seo, Jin-Soo Kim, Sung Jae Kim
The-state-of-the-art bio- and nanotechnology have opened up an avenue to non-invasive liquid biopsy for identifying diseases from biomolecules in bloodstream, especially DNA. In this work, we combined sequence-specific-labeling scheme using mutated Clustered Regularly Interspaced Short Palindromic Repeats associated protein 9 without endonuclease activity (CRISPR/dCas9) and ion concentration polarization (ICP) phenomenon as a mechanism to selectively preconcentrate targeted DNA molecules for rapid and direct detection...
November 13, 2018: Nano Letters
Fabian Mooshammer, Fabian Sandner, Markus Andreas Huber, Martin Zizlsperger, Helena Weigand, Markus Plankl, Christian Weyrich, Martin Lanius, Jörn Kampmeier, Gregor Mussler, Detlev Grützmacher, Jessica L Boland, Tyler Liam Cocker, Rupert Huber
Three-dimensional topological insulators (TIs) have attracted tremendous interest for their possibility to host massless Dirac fermions in topologically protected surface states (TSSs), which may enable new kinds of high-speed electronics. However, recent reports have outlined the importance of band bending effects within these materials, which results in an additional two-dimensional electron gas (2DEG) with finite mass at the surface. TI surfaces are also known to be highly inhomogeneous on the nanoscale, which is masked in conventional far-field studies...
November 13, 2018: Nano Letters
Spencer A Wells, Alex Henning, J Tyler Gish, Vinod K Sangwan, Lincoln J Lauhon, Mark C Hersam
With exceptional charge carrier mobilities and a direct bandgap at most thicknesses, indium selenide (InSe) is an emerging layered semiconductor that has generated significant interest for electronic and optoelectronic applications. However, exfoliated InSe nanosheets are susceptible to rapid degradation in ambient conditions, thus limiting their technological potential. In addition to morphological changes upon ambient exposure, the mobilities and current modulation on/off ratios of InSe transistors, as well as the responsivities of InSe photodetectors, decrease by over three orders of magnitude within 12 hours of ambient exposure...
November 12, 2018: Nano Letters
Achim Harzheim, Jean Spiece, Charalambos Evangeli, Edward McCann, Vladimir I Fal'ko, Yuewen Sheng, Jamie H Warner, G Andrew D Briggs, Jan A Mol, Pascal Gehring, Oleg V Kolosov
The influence of nanostructuring and quantum confinement on the thermoelectric properties of materials has been extensively studied. While this has made possible multiple breakthroughs in the achievable figure of merit, classical confinement and its effect on the local Seebeck coefficient has mostly been neglected, as has the Peltier effect in general due to the complexity of measuring small temperature gradients locally. Here we report that reducing the width of a graphene channel to 100 nanometers changes the Seebeck coefficient by orders of magnitude...
November 12, 2018: Nano Letters
Sohyun Park, Hyo Jae Yoon
A challenge in organic thermoelectrics is to relate thermoelectric performance of devices to the chemical and electronic structures of organic component inside them on a molecular scale. To this end, a reliable and reproducible platform relevant to molecular-level thermoelectric measurements is essentially needed. This paper shows a new, efficient approach for thermoelectric characterization of large-area of molecular monolayers using liquid eutectic gallium-indium (EGaIn). Cone-shaped EGaIn microelectrode permits access to non-invasive, reversible top-contact formation onto organic surfaces in ambient conditions, high yields of working devices (up to 97%), and thus statistically sufficient thermoelectric data sets (~6000 data per sample in a few hours)...
November 12, 2018: Nano Letters
Won Mo Seong, Kyungho Yoon, Myeong Hwan Lee, Sung-Kyun Jung, Kisuk Kang
No abstract text is available yet for this article.
November 12, 2018: Nano Letters
Omri Sharon, Avner Avraham Shaulov, Jorge Berger, Amos Sharoni, Richard Berkovits, Yosef Yeshurun
Magnetoresistance measurements in a granular Nb nanoring reveal current-induced crossover between two distinct quantum coherence effects. At low bias currents, Cooper-pair coherence is manifested by Little-Parks oscillations with flux periodicity of h/2 e. At high bias currents, magnetoresistance oscillations with flux periods of h/ e are observed and interpreted as Aharonov-Bohm oscillations, reflecting the phase coherence of individual quasi-particles. The model explaining these data views the ring as a chain of superconducting grains weakly coupled by tunnel junctions...
November 12, 2018: Nano Letters
Jan-Chi Yang, Yi-De Liou, Wen-Yen Tzeng, Heng-Jui Liu, Yao-Wen Chang, Ping-Hua Xiang, Zaoli Zhang, Chun-Gang Duan, Chih-Wei Luo, Yi-Chun Chen, Ying-Hao Chu
Photostriction, optical stimulus driven mechanical deformation in materials, provides a solution toward next-generation technology. Here, the giant photostriction (∼2% change of lattice) of epitaxial strontium iridate (SrIrO3 ) films under illumination at room temperature is revealed via power-dependent Raman scattering, which is significantly larger as compared to conventional inorganic materials. The time scale and mechanism of this giant photostriction in SrIrO3 are further studied through time-resolved transient reflectivity measurements...
November 12, 2018: Nano Letters
Nan Zhang, Alessandro Surrente, Michał Baranowski, Duncan K Maude, Patricia Gant, Andres Castellanos-Gomez, Paulina Plochocka
Spatially periodic structures with a long-range period, referred to as a moiré pattern, can be obtained in van der Waals bilayers in the presence of a small stacking angle or of lattice mismatch between the monolayers. Theoretical predictions suggest that the resulting spatially periodic variation of the band structure modifies the optical properties of both intra- and interlayer excitons of transition metal dichalcogenide heterostructures. Here, we report on the impact of the moiré pattern formed in a MoSe2 /MoS2 heterobilayer encapsulated in hexagonal boron nitride...
November 12, 2018: Nano Letters
John P Philbin, Eran Rabani
The fast nonradiative decay of multiexcitonic states via Auger recombination is a fundamental process affecting a variety of applications based on semiconductor nanostructures. From a theoretical perspective, the description of Auger recombination in confined semiconductor nanostructures is a challenging task due to the large number of valence electrons and exponentially growing number of excited excitonic and biexcitonic states that are coupled by the Coulomb interaction. These challenges have restricted the treatment of Auger recombination to simple, noninteracting electron-hole models...
November 12, 2018: Nano Letters
Qiao Li, Chaocheng He, Yaojia Wang, Erfu Liu, Miao Wang, Yu Wang, Junwen Zeng, Zecheng Ma, Tianjun Cao, Changjiang Yi, Naizhou Wang, Kenji Watanabe, Takashi Taniguchi, Lubing Shao, Youguo Shi, Xianhui Chen, Shi-Jun Liang, Qiang-Hua Wang, Feng Miao
Due to the nontrivial topological band structure in type II Weyl semi-metal tungsten ditelluride (WTe2 ), unconventional properties may emerge in its superconducting phase. While realizing intrinsic superconductivity has been challenging in the type II Weyl semi-metal WTe2 , the proximity effect may open an avenue for the realization of superconductivity. Here, we report the observation of proximity-induced superconductivity with a long coherence length along the c axis in WTe2 thin flakes based on a WTe2 /NbSe2 van der Waals heterostructure...
November 12, 2018: Nano Letters
Daling Cui, Maryam Ebrahimi, Jennifer M Macleod, Federico Rosei
The integration of molecules with irregular shape into a long-range, dense and periodic lattice represents a unique challenge for the fabrication of engineered molecular scale architectures. The tiling of pentagonal molecules on a two-dimensional (2D) plane can be used as a proof-of-principle investigation to overcome this problem because basic geometry dictates that a 2D surface cannot be filled with a periodic arrangement of pentagons, a fundamental limitation that suggests that pentagonal molecules may not be suitable as building blocks for dense films...
November 12, 2018: Nano Letters
John Thomas Gaskins, George Kotsonis, Ashutosh Giri, Shenghong Ju, Andrew Rohskopf, Yekan Wang, Tingyu Bai, Edward Sachet, Christopher T Shelton, Zeyu Liu, Zhe Cheng, Brian Foley, Samuel Graham, Tengfei Luo, Asegun Henry, Mark S Goorsky, Junichiro Shiomi, Jon-Paul Maria, Patrick E Hopkins
We present experimental measurements of the thermal boundary conductance (TBC) from 77 - 500 K across isolated heteroepitaxially grown ZnO films on GaN substrates. This data provides an assessment of the underlying assumptions driving phonon gas based models, such as the diffuse mismatch model (DMM), and atomistic Green's function (AGF) formalisms used to predict TBC. Our measurements, when compared to previous experimental data, suggest that TBC can be influenced by long wavelength, zone center modes in a material on one side of the interface as opposed to the "vibrational mismatch" concept assumed in the DMM; this disagreement is pronounced at high temperatures...
November 9, 2018: Nano Letters
Yong Ai, Andrii Kovalchuk, Xinkai Qiu, Yanxi Zhang, Sumit Kumar, Xintai Wang, Martin Kühnel, Kasper Nørgaard, Ryan C Chiechi
This paper describes tunneling junctions comprising self-assembled monolayers that can be converted between resistor and diode functionality in-place. The rectification ratio is affected by the hydration of densely packed carboxylic acid groups at the interface between the top-contact and the monolayer. We studied this process by treatment with water and a water scavenger using three different top-contacts, eutectic Ga-In (EGaIn), conducting-probe atomic force microscopy (CP-AFM), and reduced graphene oxide (rGO), demonstrating that the phenomena is molecular in nature and is not platform-speciffc...
November 9, 2018: Nano Letters
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