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Yan-Qiang Cao, Bing Wu, Di Wu, Ai-Dong Li
In situ-formed SiO2 was introduced into HfO2 gate dielectrics on Ge substrate as interlayer by plasma-enhanced atomic layer deposition (PEALD). The interfacial, electrical, and band alignment characteristics of the HfO2/SiO2 high-k gate dielectric stacks on Ge have been well investigated. It has been demonstrated that Si-O-Ge interlayer is formed on Ge surface during the in situ PEALD SiO2 deposition process. This interlayer shows fantastic thermal stability during annealing without obvious Hf-silicates formation...
December 2017: Nanoscale Research Letters
Qin Shi, Chen Zhang, Yuan Su, Jie Zhang, Dongshan Zhou, Ting Cai
This study aims to investigate the crystallization behavior and molecular dynamics of amorphous griseofulvin (GSF) in the presence of low-concentration poly (ethylene oxide) (PEO). We observe that the addition of 3 % w/w PEO remarkably increases the crystal growth rate of GSF by two orders of magnitude, in both the supercooled liquid and glassy states. The liquid dynamics of amorphous GSF in the presence and absence of PEO are characterized by dielectric spectroscopy. With an increase of the PEO content, the α-relaxation times of the systems decrease, indicating the increase of global molecular mobility...
May 26, 2017: Molecular Pharmaceutics
Yuchun Liu, Ling Xu, Chen Zhao, Ming Shao, Bin Hu
Fullerene (C60) is an important n-type organic semiconductor with high electron mobility and low thermal conductivity. In this work, we report the experimental results on the tunable Seebeck effect of C60 hybrid thin-film devices by adopting different oxide layers. After inserting n-type high-dielectric constant titanium oxide (TiOx) and zinc oxide (ZnO) layers, we observed a significantly enhanced n-type Seebeck effect in oxide/C60 hybrid devices with Seebeck coefficients of -5.8 mV K(-1) for TiOx/C60 and -2...
May 26, 2017: Physical Chemistry Chemical Physics: PCCP
Sampath Gamage, Alireza Fali, Neda Aghamiri, Lingming Yang, Pei-De Ye, Yohannes Abate
Black phosphorus (BP) possesses several extraordinary physical properties, which include in-plane anisotropy, thickness dependent direct bandgap and high carrier mobility. These physical properties make BP highly desirable from the point of view of fundamental science and modern optoelectronics applications. The excitement about this material has always been accompanied by unreserved skepticism due to its extraordinary degradation under ambient conditions. Here we show ambient degradation of exfoliated BP can be effectively suppressed using thin layer of hybrid MOCVD coating of BN followed by ALD coating of Al2O3...
May 26, 2017: Nanotechnology
Mario D'Acunto, Francesco Fuso, Ruggero Micheletto, Makoto Naruse, Francesco Tantussi, Maria Allegrini
The occurrence of plasmon resonances on metallic nanometer-scale structures is an intrinsically nanoscale phenomenon, given that the two resonance conditions (i.e., negative dielectric permittivity and large free-space wavelength in comparison with system dimensions) are realized at the same time on the nanoscale. Resonances on surface metallic nanostructures are often experimentally found by probing the structures under investigation with radiation of various frequencies following a trial-and-error method...
2017: Beilstein Journal of Nanotechnology
Erica Guerriero, Paolo Pedrinazzi, Aida Mansouri, Omid Habibpour, Michael Winters, Niklas Rorsman, Ashkan Behnam, Enrique A Carrion, Amaia Pesquera, Alba Centeno, Amaia Zurutuza, Eric Pop, Herbert Zirath, Roman Sordan
The high-frequency performance of transistors is usually assessed by speed and gain figures of merit, such as the maximum oscillation frequency f max, cutoff frequency f T, ratio f max/f T, forward transmission coefficient S 21, and open-circuit voltage gain A v. All these figures of merit must be as large as possible for transistors to be useful in practical electronics applications. Here we demonstrate high-performance graphene field-effect transistors (GFETs) with a thin AlOx gate dielectric which outperform previous state-of-the-art GFETs: we obtained f max/f T > 3, A v > 30 dB, and S 21 = 12...
May 25, 2017: Scientific Reports
Edwin Lok, Pyay San, Van Hua, Melissa Phung, Eric T Wong
Tumor Treating Fields (TTFields) therapy is an approved treatment that has known clinical efficacy against recurrent and newly diagnosed glioblastoma. However, the distribution of the electric fields and the corresponding pattern of energy deposition in the brain are poorly understood. To evaluate the physical parameters that may influence TTFields, postacquisition MP-RAGE, T1 and T2 MRI sequences from a responder with a right parietal glioblastoma were anatomically segmented and then solved using finite-element method to determine the distribution of the electric fields and rate of energy deposition at the gross tumor volume (GTV) and other intracranial structures...
May 23, 2017: Cancer Medicine
Albert F Rigosi, Nicholas R Glavin, Chieh-I Liu, Yanfei Yang, Jan Obrzut, Heather M Hill, Jiuning Hu, Hsin-Yen Lee, Angela R Hight Walker, Curt A Richter, Randolph E Elmquist, David B Newell
Regarding the improvement of current quantized Hall resistance (QHR) standards, one promising avenue is the growth of homogeneous monolayer epitaxial graphene (EG). A clean and simple process is used to produce large, precise areas of EG. Properties like the surface conductivity and dielectric loss tangent remain unstable when EG is exposed to air due to doping from molecular adsorption. Experimental results are reported on the extraction of the surface conductivity and dielectric loss tangent from data taken with a noncontact resonance microwave cavity, assembled with an air-filled, standard R100 rectangular waveguide configuration...
May 19, 2017: Small
Kirsten Koolstra, Peter Börnert, Wyger Brink, Andrew Webb
PURPOSE: To explore the effect of using extremely high permittivity (εr ∼1,000) materials on image quality and power requirements of spine imaging at 3 T. THEORY AND METHODS: A linear array of high permittivity dielectric blocks made of lead zirconate titanate (PZT) was designed and characterized by electromagnetic simulations and experiments. Their effect on the transmit efficiency, receive sensitivity, power deposition, and diagnostic image quality was analyzed in vivo in 10 healthy volunteers...
May 22, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Garron Deshazer, Mark Hagmann, Derek Merck, Jan Sebek, Kent B Moore, Punit Prakash
PURPOSE: The objective of this study is to develop a computational model for simulating 915 MHz microwave ablation (MWA), and verify the simulation predictions of transient temperature profiles against experimental measurements. Due to the limited experimental data characterizing temperature-dependent changes of tissue dielectric properties at 915 MHz, we comparatively assess two temperature dependent approaches of modeling of dielectric properties: model A- piecewise linear temperature dependencies based on existing, but limited, experimental data, and model B- similar to model A, but augmented with linear decrease in electrical conductivity above 95 °C, as guided by our experimental measurements...
May 23, 2017: Medical Physics
Tomer Lewi, Hayden A Evans, Nikita A Butakov, Jon A Schuller
Subwavelength Mie resonators have enabled new classes of optical antenna and nanophotonic devices and can act as the basic meta-atoms constituents of low-loss dielectric metasurfaces. In any application, tunable Mie resonances are key to achieving dynamic and reconfigurable operation. However, active tuning of these nanoantennas is still limited and usually results in sub-linewidth resonance tuning. Here, we demonstrate ultra-wide dynamic tuning of PbTe Mie resonators fabricated via both laser ablation and a novel solution-processing approach...
May 25, 2017: Nano Letters
Tumpa Sadhukhan, Dharitri Das, Pratik Kalekar, Vidya Avasare, Sourav Pal
Triose sugar, 1,3-Dihydroxy acetone (DHA) on treatment with Fenton's reagent releases CO under physiological conditions. The release of CO has been demonstrated by myoglobin assay and quantum chemical studies. The mechanistic study has been carried out using B3LYP/6-311++G(d,p), M06-2X/6-311++G(d,p) and CCSD(T)//M06-2X/6-311++G(d,p) level of theories in aqueous medium with dielectric constant of 78.39 by employing polarized continuum model (PCM). The theoretical investigation shows that DHA breaks down completely into two equivalents of CO, one equivalent of CO2 and six equivalents of H2O without formation of toxic metabolites...
May 25, 2017: Journal of Physical Chemistry. A
Michael Hollerer, Daniel Lüftner, Philipp Hurdax, Thomas Ules, Serguei Soubatch, Frank Stefan Tautz, Georg Koller, Peter Puschnig, Martin Sterrer, Michael G Ramsey
It is becoming accepted that ultra-thin dielectric layers on metals are not merely passive decoupling layers, but can actively influence orbital energy level alignment and charge transfer at interfaces. As such, they can be important in applications ranging from catalysis to organic electronics. However, the details at the molecular level are still under debate. In this study, we present a comprehensive analysis of the phenomenon of charge transfer promoted by a dielectric interlayer with a comparative study of pentacene adsorbed on Ag(001) with and without an ultra-thin MgO interlayer...
May 25, 2017: ACS Nano
Semi Oh, Kwang Jae Lee, Sang-Jo Kim, Kab Ha, Jongyeul Jeong, Dongjun Kim, Kyoung-Kook Kim, Seong-Ju Park
The control of the refractive index and electrical conductivity in the dielectric layer of omnidirectional reflectors (ODRs) is essential to improve the low efficiency of AlGaN-based UV emitters. Here, we report self-assembled indium tin oxide (ITO) nanoball-embedded omnidirectional reflectors (NODRs) for use in high-efficiency AlGaN-based UV emitters at 365 nm. These NODRs consisted of a reflective Al layer, a self-assembled conducting ITO nanoball layer for current injection and spreading, and nanovoids that provided a low refractive index to achieve highly efficient UV emitters...
May 25, 2017: Nanoscale
K Adrjanowicz, G Szklarz, K Koperwas, M Paluch
High pressure and nanoscopic confinement are two different strategies commonly employed to modify the physicochemical properties of various materials. Both strategies act mostly by changing the molecular packing. In this work, we performed a comparative study on the effect of compression and confined geometry on crystallization of a molecular liquid. Dielectric spectroscopy was employed to investigate the crystallization of the van der Waals liquid, dimethyl phthalate, in nanoporous alumina of different pore sizes as well as on increased pressure (up to 200 MPa)...
May 25, 2017: Physical Chemistry Chemical Physics: PCCP
Xu Qiu, Lixi Wang, Hongli Zhu, Yongkang Guan, Qitu Zhang
Lightweight microwave absorbing materials have drawn tremendous attention. Herein, nano-porous biomass carbon materials have been prepared by carbonization with a subsequent potassium hydroxide activation of walnut shells and the microwave absorption properties have also been investigated. The obtained samples have large specific surface areas with numerous micropores and nanopores. The sample activated at 600 °C with a specific surface area of 736.2 m(2) g(-1) exhibits the most enhanced microwave absorption performance...
May 25, 2017: Nanoscale
Nicholas P Brawand, Marco Govoni, Márton Vörös, Giulia Galli
We analyze the performance of the recently proposed screened exchange constant functional (SX) (Phys. Rev. X \textbf{2016}, 10, 642) on the GW100 test set, and we discuss results obtained at different levels of self-consistency. The SX functional is a generalization of dielectric dependent hybrid functionals to finite systems, it is non-empirical and depends on the average screening of the exchange interaction. We compare results for ionization potentials obtained with SX to those of CCSD(T) calculations and experiments and we find excellent agreement, on par with recent state of the art methods based on many body perturbation theory...
May 24, 2017: Journal of Chemical Theory and Computation
Liancheng Wang, Zhiqiang Liu, Zhi Li, Yiyun Zhang, Hongjian Li, Xiaoyan Yi, Junxi Wang, Guohong Wang, Jinmin Li
We report here a new approach of Talbot effect based colloidal photolithography for fabricating nanostructure light emitting diodes (LEDs). By employing a rigid metal nanohole array template (RDT) as the diffraction grating and a polysiloxane-based spin on dielectric (SOD) as the thickness-controllable spacer layer, various InGaN/GaN nanostructure LEDs have been fabricated. Three-dimensional finite-difference time-domain (3D-FDTD) simulations have been conducted to verify the proposed approach. Photoluminescence (PL) and time-resolved photoluminescence (TRPL) have been performed to investigate the optical properties of the obtained nanostructure LEDs...
May 24, 2017: Nanoscale
J C Everts, S Samin, N A Elbers, J E S van der Hoeven, A van Blaaderen, R van Roij
We theoretically and experimentally investigate colloid-oil-water-interface interactions of charged, sterically stabilized, poly(methyl-methacrylate) colloidal particles dispersed in a low-polar oil (dielectric constant ε = 5-10) that is in contact with an adjacent water phase. In this model system, the colloidal particles cannot penetrate the oil-water interface due to repulsive van der Waals forces with the interface whereas the multiple salts that are dissolved in the oil are free to partition into the water phase...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
Bingcheng Luo, Xiaohui Wang, Enke Tian, Hongzhou Song, Hongxian Wang, Longtu Li
A novel lead-free (1-x) CaTiO3-xBiScO3 linear dielectric ceramic with enhanced energy storage density was fabricated. With the composition of BiScO3 increasing, the dielectric constant of (1-x)CaTiO3-xBiScO3 ceramics firstly increased and then decreased after the composition x>0.1, while the dielectric loss decreased firstly and increased. For the composition x=0.1, the polarization was increased into 12.36 μC/cm2, 4.6 times higher than that of the pure CaTiO3. The energy density of 0.9 CaTiO3-0.1 BiScO3 ceramic was 1...
May 24, 2017: ACS Applied Materials & Interfaces
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