Switching mechanism in two-terminal vanadium dioxide devices

Two-terminal thin film VO 2 devices show an abrupt decrease of resistance when the current or voltage applied exceeds a threshold value. This phenomenon is often described as a field-induced metal–insulator transition. We fabricate nano-scale devices with different electrode separations down to 100 nm and study how the dc switching voltage and current depend on device size and temperature. Our observations are consistent with a Joule heating mechanism governing the switching. Pulsed measurements show a switching time to the high resistance state of the order of one hundred nanoseconds, consistent with heat dissipation time. In spite of the Joule heating mechanism which is expected to induce device degradation, devices can be switched for more than 10 10 cycles making VO 2 a promising material for nanoelectronic applications.

Iuliana P Radu, B Govoreanu, S Mertens, X Shi, M Cantoro, M Schaekers, M Jurczak, S De Gendt, A Stesmans, J A Kittl, M Heyns and K Martens

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A simple criterion for determining the static friction force between nanowires and flat substrates using the most-bent-state method

A simple criterion was developed to assess the appropriateness of the currently available models that estimate the static friction force between nanowires and substrates using the ‘most-bent-state’ method. Our experimental testing of the static friction force between Al 2 O 3 nanowires and Si substrate verified our theoretical analysis, as well as the establishment of the criterion. It was found that the models are valid only for the bent nanowires with the ratio of wire length over the minimum curvature radius ##IMG## [http://ift.tt/1bB8pnA] {$\left( L/{{R}_{O}} \right)$} no greater than 1. For the cases with ##IMG## [http://ift.tt/1NhE23c] {$L/{{R}_{O}}$} greater than 1, the static friction force was overestimated as it neglected the effect of its tangential component.

Lizhen Hou, Shiliang Wang and Han Huang

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Pure, single crystal Ge nanodots formed using a sandwich structure via pulsed UV excimer laser annealing

In this paper, a sandwich structure comprising a SiO 2 capping layer, amorphous Germanium (a-Ge) nanodots (NDs), and a pit-patterned Silicon (Si) substrate is developed, which is then annealed by utilizing a pulsed ultraviolet excimer laser in order to fabricate an array of pure, single crystal Ge NDs at room temperature. A wide bandgap SiO 2 capping layer is used as a transparent thermally isolated layer to prevent thermal loss and Si–Ge intermixing. The two-dimensional pit-patterned Si substrate is designed to confine the absorbed laser energy, reduce the melting point, and block the surface migration of the Ge. After optimizing the laser radiation parameters such that the laser energy density is 200 mJ cm −2 , the laser annealing period is 10 s, and the number of laser shots is 10, pure, single crystal Ge NDs that have both a regular arrangement and a uniform size distribution are obtained in the pits of the Si substrates. The Raman spectrum shows ...

Ting-Wei Liao, Hung-Ming Chen, Kuan-Yuan Shen and Chieh-Hsiung Kuan

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Optimized electrospinning synthesis of iron–nitrogen–carbon nanofibers for high electrocatalysis of oxygen reduction in alkaline medium

To achieve iron–nitrogen–carbon (Fe–N–C) nanofibers with excellent electrocatalysis for replacing high-cost Pt-based catalysts in the cathodes of fuel cells and metal-air batteries, we have investigated and evaluated the effects of polyacrylonitrile (PAN) concentration and the proportion of iron to PAN, along with voltage and flow rate during the electrospinning process, and thus proposed three criteria to optimize these parameters for ideal nanofiber catalysts. The best half-wave potential of an optimized catalysts is 0.82 V versus reversible hydrogen electrode in an alkaline medium, which reaches the best range of the non-precious-metal catalysts reported and is very close to that of commercial Pt/C catalysts. Furthermore, the electron-transfer number of our catalysts is superior to that of the Pt/C, indicating the catalysts undergo a four-electron process. The durability of the optimized Fe–N–C nanofibers is also better than that of the Pt/C, which is attributed to the homogen...

Xingxu Yan, Kexi Liu, Xiangqing Wang, Tuo Wang, Jun Luo and Jing Zhu

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Oscillatory motion in layered materials: graphene, boron nitride, and molybdenum disulfide

Offset-driven self-retraction and oscillatory motion of bilayer graphene has been observed experimentally and is potentially relevant for nanoscale technological applications. In a previous article, we showed that friction between laterally offset graphene layers is controlled by roughness and proposed a simple reduced-order model based on density-functional theory (DFT) and molecular dynamics (MD) data, with which predictions on the experimental size-scale could be made. In this article, we extend our study to other layered materials, with emphasis on boron nitride (BN) and molybdenum disulfide (MoS 2 ). Using MD and DFT simulations of these systems and a generalized version of the reduced-order model, we predict that BN will exhibit behavior similar to graphene (heavily-damped oscillation with a decay rate that increases with roughness) and that MoS 2 shows no oscillatory behavior even in the absence of roughness. This is attributed to the higher energy barri...

Zhijiang Ye, Alberto Otero-de-la-Roza, Erin R Johnson and Ashlie Martini

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Electric Field Control of Spin-Dependent Dissipative Electron Transfer Dynamics in Mixed-Valence Molecules

The Journal of Physical Chemistry C

DOI: 10.1021/jp512102n

A. V. Palii, J. M. Clemente-Juan, E. Coronado and B. Tsukerblat

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Light Harvesting and Charge Recombination in CH3NH3PbI3 Perovskite Solar Cells Studied by Hole Transport Layer Thickness Variation

ACS Nano

DOI: 10.1021/acsnano.5b00447

Nevena Marinova, Wolfgang Tress, Robin Humphry-Baker, M. Ibrahim Dar, Vladimir Bojinov, Shaik Mohammed Zakeeruddin, Mohammad Khaja Nazeeruddin and Michael Grätzel

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Monolayer-Precision Synthesis of Molybdenum Sulfide Nanoparticles and Their Nanoscale Size Effects in the Hydrogen Evolution Reaction

ACS Nano

DOI: 10.1021/acsnano.5b00786

Bora Seo, Gwan Yeong Jung, Young Jin Sa, Hu Young Jeong, Jae Yeong Cheon, Jeong Hyeon Lee, Ho Young Kim, Jin Chul Kim, Hyeon Suk Shin, Sang Kyu Kwak and Sang Hoon Joo

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Insights into the Transport of Alkali Metal Ions Doped into a Plastic Crystal Electrolyte

Chemistry of Materials

DOI: 10.1021/acs.chemmater.5b00538

Fangfang Chen, Jennifer M. Pringle and Maria Forsyth

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Superconductivity in Single Crystals of Lu3T4Ge13–x (T = Co, Rh, Os) and Y3T4Ge13–x (T = Ir, Rh, Os)

Chemistry of Materials

DOI: 10.1021/cm504658h

Binod K. Rai, Iain W. H. Oswald, Jiakui K. Wang, Gregory T. McCandless, Julia Y. Chan and E. Morosan

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Highly Efficient Electron Transport Obtained by Doping PCBM with Graphdiyne in Planar-Heterojunction Perovskite Solar Cells

Nano Letters

DOI: 10.1021/acs.nanolett.5b00787

Chaoyang Kuang, Gang Tang, Tonggang Jiu, Hui Yang, Huibiao Liu, Bairu Li, Weining Luo, Xiaodong Li, Wenjun Zhang, Fushen Lu, Junfeng Fang and Yuliang Li

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Nano-Scale Corrugations in Graphene: A Density Functional Theory Study of Structure, Electronic Properties and Hydrogenation

The Journal of Physical Chemistry C

DOI: 10.1021/jp511409b

Antonio Rossi, Simone Piccinin, Vittorio Pellegrini, Stefano de Gironcoli and Valentina Tozzini

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Branched Segments in Polymer Gate Dielectric as Intrinsic Charge Trap Sites in Organic Transistors

The Journal of Physical Chemistry C

DOI: 10.1021/acs.jpcc.5b01522

Junghwi Lee, Hyun Ho Choi, Namwoo Park, Honggi Min, Singu Han, Heejeong Jeong, Inseok Song, Se Hyun Kim and Hwa Sung Lee

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Penn Algorithm Including Damping for Calculating the Electron Inelastic Mean Free Path

The Journal of Physical Chemistry C

DOI: 10.1021/acs.jpcc.5b00403

Hieu T. Nguyen-Truong

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Atomistic Simulations of Coating of Silver Nanoparticles with Poly(vinylpyrrolidone) Oligomers: Effect of Oligomer Chain Length

The Journal of Physical Chemistry C

DOI: 10.1021/jp510369a

Alexander Kyrychenko, Oleksandr M. Korsun, Iurii I. Gubin, Sergiy M. Kovalenko and Oleg N. Kalugin

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Hydrogen Adsorption and Storage in Heteroatoms (B, N) Modified Carbon-Based Materials Decorated with Alkali Metals: A Computational Study

The Journal of Physical Chemistry C

DOI: 10.1021/acs.jpcc.5b01416

Hsien-Wei Huang, Han-Ju Hsieh, I-Hsiang Lin, Yu-Jhe Tong and Hsin-Tsung Chen

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Gold Nanocube–Nanosphere Dimers: Preparation, Plasmon Coupling, and Surface-Enhanced Raman Scattering

The Journal of Physical Chemistry C

DOI: 10.1021/acs.jpcc.5b00314

Daedu Lee and Sangwoon Yoon

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Structural Study of Mg-Based Metal–Organic Frameworks by X-ray Diffraction, 1H, 13C, and 25Mg Solid-State NMR Spectroscopy, and First-Principles Calculations

The Journal of Physical Chemistry C

DOI: 10.1021/acs.jpcc.5b01381

Gregor Mali, Julien Trebosc, Charlotte Martineau and Matjaž Mazaj

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The “Surface Optical” Phonon in CdSe Nanocrystals

ACS Nano

DOI: 10.1021/nn5008513

Chen Lin, David F. Kelley, Mikaela Rico and Anne Myers Kelley

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Higher Open Circuit Voltage and Reduced UV-Induced Reverse Current in ZnO-Based Solar Cells by a Chemically Modified Blocking Layer

The Journal of Physical Chemistry C

DOI: 10.1021/jp5004209

Eran Edri, Nir Kedem, Hagai Cohen, Piers Barnes and Gary Hodes

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