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Kaixuan Zhang, Lin Li, Hui Li, Qiyuan Feng, Nan Zhang, Long Cheng, Xiaodong Fan, Yubin Hou, Qingyou Lu, Zhenyu Zhang, Changgan Zeng
One-dimensional (1D) confinement has been revealed to effectively tune the properties of materials in homogeneous states. The 1D physics can be further enriched by electronic inhomogeneity, which unfortunately remains largely unknown. Here we demonstrate the ultra-high sensitivity to magnetic fluctuations and the tunability of phase stability in the electronic transport properties of self-assembled electronically phase-separated manganite nanowires with extreme aspect ratio. The onset of magnetic nano-droplet state, a precursor to the ferromagnetic metallic state, is unambiguously revealed, which is attributed to the small lateral size of the nanowires that is comparable to the droplet size...
February 23, 2017: Nano Letters
Xiang Liu, Li Yin, Wenbo Mi
The Verwey transition in Fe3O4 is the first metal-insulator transition caused by charge ordering. However, the physical mechanism and influence factors of Verwey transition are still debated. Herewith, the strain effects on the electronic structure of low-temperature phase (LTP) Fe3O4 with P2/c and Cc symmetries are investigated by first-principles calculations. LTP Fe3O4 with each space group has a critical strain. With P2/c, Fe3O4 is sensitive to the compressive strain, but it is sensitive to tensile strain for Cc...
February 23, 2017: Scientific Reports
Zhongguang Xu, Hao Tian, Alireza Khanaki, Renjing Zheng, Mohammad Suja, Jianlin Liu
Two-dimensional (2D) hexagonal boron nitride (h-BN), which has a similar honeycomb lattice structure to graphene, is promising as a dielectric material for a wide variety of potential applications based on 2D materials. Synthesis of high-quality, large-size and single-crystalline h-BN domains is of vital importance for fundamental research as well as practical applications. In this work, we report the growth of h-BN films on mechanically polished cobalt (Co) foils using plasma-assisted molecular beam epitaxy...
February 23, 2017: Scientific Reports
Emil Prodan, Kyle Dobiszewski, Alokik Kanwal, John Palmieri, Camelia Prodan
Mechanical systems can display topological characteristics similar to that of topological insulators. Here we report a large class of topological mechanical systems related to the BDI symmetry class. These are self-assembled chains of rigid bodies with an inversion centre and no reflection planes. The particle-hole symmetry characteristic to the BDI symmetry class stems from the distinct behaviour of the translational and rotational degrees of freedom under inversion. This and other generic properties led us to the remarkable conclusion that, by adjusting the gyration radius of the bodies, one can always simultaneously open a gap in the phonon spectrum, lock-in all the characteristic symmetries and generate a non-trivial topological invariant...
February 23, 2017: Nature Communications
Mohammad Mahdi Eftekharian, Tahereh Azimi, Soudeh Ghafouri-Fard, Arezou Sayad, Mir Davood Omrani, Shaghayegh Sarrafzadeh, Roghayeh Abbasalipourkabir, Mehrdokht Mazdeh, Mohammad Taheri
Multiple sclerosis (MS) is a chronic disorder resulting from destruction of the myelin or insulating covers of neurons in the central nervous system (CNS). Several lines of evidence suggest a role for immune response in the occurrence and progression of this disorder. Several disease-modifying agents (DMA) including β-interferons (IFNβ) are being used in MS patients in order to stop the disease at the early inflammatory stage, postpone disease progression and diminish future disability. Phospholipase D1 (PLD1) is a critical enzyme responsible for the making lipid second messenger phosphatidic acid...
February 22, 2017: Neurological Sciences
Yan Liu, Jiebin Niu, Hongjuan Wang, Genquan Han, Chunfu Zhang, Qian Feng, Jincheng Zhang, Yue Hao
Well-behaved Ge quantum well (QW) p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) were fabricated on silicon-on-insulator (SOI) substrate. By optimizing the growth conditions, ultrathin fully strained Ge film was directly epitaxially grown on SOI at about 450 °C using ultra-high vacuum chemical vapor deposition. In situ Si2H6 passivation of Ge was utilized to form a high-quality SiO2/Si interfacial layer between the high-κ dielectric and channels. Strained Ge QW pMOSFETs achieve the significantly improved effective hole mobility μ eff as compared with the relaxed Si and Ge control devices...
December 2017: Nanoscale Research Letters
Mikhail Kozlov, Gregor Schaefers, Mikhail Kozlov, Gregor Schaefers, Gregor Schaefers, Mikhail Kozlov
Radio frequency (RF) induced power deposition near straight insulated leads excited by different incident electrical field profiles was investigated. 3-D electromagnetic (EM) simulations were used to obtain implant models as well as RF-induced power depositions calculated as the integral of power loss density. For the investigated setups up to 400% discrepancy between the implant model predictions and EM simulation values was observed.
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Mikhail Kozlov, Gregor Schaefers, Mikhail Kozlov, Gregor Schaefers, Gregor Schaefers, Mikhail Kozlov
We investigated RF-induced power deposition (p) generated by insulated leads with different lengths located in proximity to two tissues. The first tissue surrounding the leads was shaped as a cylinder with a diameter of 11 mm and located in a very large box filled with the second tissue. Lead electromagnetic models and p substantially depended on electrical properties of both tissues. If the cylinder and the box were filled with the same tissue, discrepancy to results of the two-tissue setup was up to 280%.
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
P Cvancara, S Lauser, L Rudmann, T Stieglitz, P Cvancara, S Lauser, L Rudmann, T Stieglitz, P Cvancara, S Lauser, T Stieglitz, L Rudmann
The microflex interconnection (MFI) technique is often used to connect electrically and mechanically thin film ribbons or electrodes with a solid substrate like screen printed ceramics. For stabilization reasons epoxy is used to fix the MFI structure. As epoxy tends to form cracks when surrounded by water or electrolytes we are eager to find an epoxy which provides sufficient insulation between the single channels of the MFI structure also in a moist surrounding. Therefore we designed a device to investigate the insulating properties of different epoxies (Uhu Plus Endfest 300, Epo-Tek 353ND and 353ND-T) immersed in saline solution...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Mattias Borg, Heinz Schmid, Johannes Gooth, Marta D Rossell, Davide Cutaia, Moritz Knoedler, Nicolas Bologna, Stephan Wirths, Kirsten E Moselund, Heike Riel
GaSb nanostructures integrated on Si substrates are of high interest for p-type transistors and mid-IR photodetectors. Here, we investigate the MOCVD growth and properties of GaSb nanostructures monolithically integrated onto silicon-on-insulator wafers using template-assisted selective epitaxy. A high degree of morphological control allows for GaSb nanostructures with critical dimensions down to 20 nm. Detailed investigation of growth parameters reveals that the GaSb growth rate is governed by the desorption processes of an Sb surface, and in turn is insensitive to changes in material transport efficiency...
February 22, 2017: ACS Nano
Xiaojuan Yu, Hua Hou, Baoshan Wang
Developing the environment-friendly insulation gases to replace sulfur hexafluoride (SF6 ) has attracted considerable experimental and theoretical attentions but without success. A computational methodology was presented herein for prediction on dielectric strength and boiling point of arbitrary gaseous molecules in the purpose of molecular design and screening. New structure-activity relationship (SAR) models have been established by combining the density-dependent properties of the electrostatic potential surface, including surface area and the statistical variance of the surface potentials, with the molecular properties including polarizability, electronegativity, and hardness...
April 15, 2017: Journal of Computational Chemistry
Xiaofeng Liu, Qiangbing Guo, Jianrong Qiu
Low-dimensional (LD) materials demonstrate intriguing optical properties, which lead to applications in diverse fields, such as photonics, biomedicine and energy. Due to modulation of electronic structure by the reduced structural dimensionality, LD versions of metal, semiconductor and topological insulators (TIs) at the same time bear distinct nonlinear optical (NLO) properties as compared with their bulk counterparts. Their interaction with short pulse laser excitation exhibits a strong nonlinear character manifested by NLO absorption, giving rise to optical limiting or saturated absorption associated with excited state absorption and Pauli blocking in different materials...
February 22, 2017: Advanced Materials
S Poran, T Nguyen-Duc, A Auerbach, N Dupuis, A Frydman, Olivier Bourgeois
The superconductor-insulator transition (SIT) is considered an excellent example of a quantum phase transition that is driven by quantum fluctuations at zero temperature. The quantum critical point is characterized by a diverging correlation length and a vanishing energy scale. Low-energy fluctuations near quantum criticality may be experimentally detected by specific heat, cp, measurements. Here we use a unique highly sensitive experiment to measure cp of two-dimensional granular Pb films through the SIT. The specific heat shows the usual jump at the mean field superconducting transition temperature marking the onset of Cooper pairs formation...
February 22, 2017: Nature Communications
Weihan Li, Shuhe Hu, Xiangyu Luo, Zhongling Li, Xizhen Sun, Minsi Li, Fanfan Liu, Yan Yu
Red phosphorus (P) has attracted intense attention as promising anode material for high-energy density sodium-ion batteries (NIBs), owing to its high sodium storage theoretical capacity (2595 mAh g(-1) ). Nevertheless, natural insulating property and large volume variation of red P during cycling result in extremely low electrochemical activity, leading to poor electrochemical performance. Herein, the authors demonstrate a rational strategy to improve sodium storage performance of red P by confining nanosized amorphous red P into zeolitic imidazolate framework-8 (ZIF-8) -derived nitrogen-doped microporous carbon matrix (denoted as P@N-MPC)...
February 22, 2017: Advanced Materials
Jörg Wunderlich
No abstract text is available yet for this article.
February 22, 2017: Nature Materials
Mustafa M Fadlelmula, Engin C Sürmeli, Mehdi Ramezani, T Serkan Kasırga
Controlling solid state phase transitions via external stimuli offers rich physics along with possibilities of unparalleled applications in electronics and optics. The well-known metal-insulator transition (MIT) in vanadium dioxide (VO2) is one instance of such phase transitions emerging from strong electronic correlations. Inducing the MIT using electric field has been investigated extensively for the applications in electrical and ultrafast optical switching. However, as the Thomas-Fermi screening length is very short, for considerable alteration in the material's properties with electric field induced MIT, crystals below 10 nm are needed...
February 23, 2017: Nano Letters
Hui Wang, D Lu, J Kim, Z Wang, S T Pi, R Q Wu
Topological insulators hold great potential for efficient information processing and storage. Using density functional theory calculations, we predict that a honeycomb lead monolayer can be stabilized on an Al2O3 (0001) substrate to become topologically non-trivial with a sizeable band gap (∼0.27 eV). Furthermore, we propose to use a hexagonal boron-nitride (h-BN) monolayer as a protection for the topological states of Pb/Al2O3 and Sn/Al2O3. Our findings suggest new possibilities for designing and protecting two-dimensional TIs for practical applications...
February 21, 2017: Nanoscale
Maciej Jankowski, Daniel Kaminski, Kurt Vergeer, Marta Mirolo, Francesco Carla, A Rijnders, Tjeerd R J Bollmann
We demonstrate the controlled growth of Bi(110) and Bi(111) films on an α-Al<sub>2</sub>O<sub>3</sub>(0001) substrate by surface X-ray diffraction and X-ray reflectivity using synchrotron radiation. At temperatures as low as 40K, unanticipated pseudo-cubic Bi(110) films are grown with thicknesses ranging from a few to tens of nanometers. The roughness at the film-vacuum as well as the film-substrate interface, can be reduced by mild heating, where a crystallographic orientation transition of Bi(110) towards Bi(111) is observed at 400K...
February 21, 2017: Nanotechnology
J A Crosse
Topological insulators subject to a time-reversal-symmetry-breaking perturbation are predicted to display a magneto-electric effect that causes the electric and magnetic induction fields to mix at the material's surface. This effect induces polarization rotations of between ≈1-10 mrad per interface in an incident plane-polarized electromagnetic wave normal to a multilayered structure. Here we show, theoretically and numerically, that by using a waveguide geometry with a topological insulator guide layer and magneto-dielectric cladding it is possible to achieve rotations of ≈100 mrad and generate an elliptical polarization with only a three-layered structure...
February 21, 2017: Scientific Reports
Jerome T Mlack, Paul Masih Das, Gopinath Danda, Yung-Chien Chou, Carl H Naylor, Zhong Lin, Néstor Perea López, Tianyi Zhang, Mauricio Terrones, A T Charlie Johnson, Marija Drndić
A facile transfer process for transition metal dichalcogenide WS2 flakes is reported and the effect of the underlying substrate on the flake properties is investigated using Raman spectroscopy. The flakes are transferred from their growth substrate using polymethyl methacrylate (PMMA) and a wet etch to allow the user to transfer the flakes to a final substrate using a microscope and micromanipulator combined with semi-transparent Kapton tape. The substrates used range from insulators such as industry standard high-k dielectric HfO2 and "green polymer" parylene-C, to conducting chemical vapor deposition (CVD) grown graphene...
February 21, 2017: Scientific Reports
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