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Attribution of Fano resonant features to plasmonic particle size, lattice constant, and dielectric wavenumber in square nanoparticle lattices

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photonics Research 2014年第1期2卷 15-23页

作者： Drew DeJarnette Justin Norman D.Keith Roper Microelectronics and Photonics Graduate Program University of ArkansasFayettevilleArkansas 72701USA Department of Chemical Engineering University of ArkansasFayettevilleArkansas 72701USA

Fano resonances between plasmons and diffracted light offer tunable energies and locales,but attribution of Fano resonance features to geometry and physicochemistry of metal nanostructures and adjacent dielectrics has been confounded by complexity and computational *** work shows predictable modal shifts of Fano resonance in square lattices of plasmonic nanostructures can be attributed directly to changes in medium wavenumber,particle size,and lattice constant that alter plasmon polarizability and diffractive *** 45 to 80 nm radius particles,a window of lattice constants that support Fano resonances is identified in a range from 500 to 900 *** constants that support high intensity resonances are determined by individual particle polarizability and medium *** resonance wavelengths redshift from diffracted photon energies as local refractive index(RI)changes due to coupling with particle polarizability in the *** sensitivities for quadrupole,dipole,and Fano resonances are 150,348,and 541 nm,respectively,per RI *** resonance intensity may be enhanced more than tenfold by selecting nanoparticle sizes and lattice *** quantitative effects of such parametric changes are rapidly and intuitively distinguished using a semi-analytic approach,consisting of an exact expression for particle polarizability,a trigonometric description of diffraction,and a semianalytical coupled dipole approximation.

关键词： lattice particle wave

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Enhancement of material quality of (Si)GeSn films grown by SnCl4 precursor 228

Enhancement of material quality of (Si)GeSn films grown by S...

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Symposium on Semiconductors, Dielectrics, and Metals for Nanoelectronics 13 - 228th ECS Meeting

作者： Mosleh, A. Alher, M. Cousar, L. Abu-Safe, H. Dou, W. Grant, P.C. Al-Kabi, S. Ghetmiri, S.A. Alharthi, B. Tran, H. Du, W. Benamara, M. Li, B. Mortazavi, M. Yu, S.-Q. Naseem, H. Microelectronics-Photonics Program University of Arkansas FayettevilleAR72701 United States Electrical Engineering Department University of Arkansas FayettevilleAR72701 United States Mechanical Engineering Department University of Kerbala Kerbala Iraq Arktonics LLC FayettevilleAR72701 United States Department of Physics Wasit University Kut Iraq Institute for Nanoscience and Engineering University of Arkansas FayettevilleAR72701 United States Department of Chemistry and Physics University of Arkansas Pine Bluff Pine BluffAR71601 United States

ISBN: (纸本)9781607685395

The (Si)GeSn films have been grown with and without carrier gases on Si substrate using a cold-wall ultra-high vacuum chemical vapor deposition system. Material characterization of the films grown with Ar carrier gas using X-ray diffraction and transmission electron microscopy shows achievement of higher quality films. Optical characterization of the films with photoluminescence shows enhancement in material quality of the films at 350 and 400°C growth temperatures. Increase in the pressure results in higher Sn incorporation and higher photoluminescence intensity. Spectroscopic ellipsometry data confirms the change in the GeSn bandgap towards lower energies. © The Electrochemical Society.

关键词： High resolution transmission electron microscopy

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Direct growth of Ge_1-xSn_x films on Si using a cold-wall ultra-high vacuum chemical-vapor-deposition system

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FRONTIERS IN MATERIALS 2015年 2卷

作者： Mosleh, Aboozar Alher, Murtadha A. Cousar, Larry C. Du, Wei Ghetmiri, Seyed Amir Pham, Thach Grant, Joshua M. Sun, Greg Soref, Richard A. Li, Baohua Naseem, Hameed A. Yu, Shui-Qing Microelectronics-Photonics Graduate Program (μEP) University of Arkansas Fayetteville AR USA Department of Electrical Engineering University of Arkansas Fayetteville AR USA Mechanical Engineering Department University of Karbala Karbala Iraq Arktonics LLC Fayetteville AR USA Engineering-Physics Department Southern Arkansas University Magnolia AR USA Department of Engineering University of Massachusetts Boston Boston MA USA

Germanium tin alloys were grown directly on Si substrate at low temperatures using a cold wall ultra-high vacuum chemical-vapor-deposition system. Epitaxial growth was achieved by adopting commercial gas precursors of germane and stannic chloride without any carrier gases. The X-ray diffraction analysis showed the incorporation of Sn and that the Gei,Sn, films are fully epitaxial and strain relaxed. Tin incorporation in the Ge matrix was found to vary from 1 to 7%. The scanning electron microscopy images and energy-dispersive X-ray spectra maps show uniform Sn incorporation and continuous film growth. Investigation of deposition parameters shows that at high flow rates of stannic chloride the films were etched due to the production of HCI. The photoluminescence study shows the reduction of band-gap from 0.8 to 0.55 eV as a result of Sn incorporation.

关键词： chemical-vapor-deposition Si photonics Ge alloys photoluminescence Ge-Sn

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CMOS compatible growth of high quality Ge, SiGe and SiGeSn for photonic device applications 228

CMOS compatible growth of high quality Ge, SiGe and SiGeSn f...

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Symposium on Semiconductors, Dielectrics, and Metals for Nanoelectronics 13 - 228th ECS Meeting

作者： Alher, M. Mosleh, A. Cousar, L. Dou, W. Grant, P.C. Ghetmiri, S.A. Al-Kabi, S. Du, W. Benamara, M. Li, B. Mortazavi, M. Yu, S.-Q. Naseem, H.A. Electrical Engineering Department University of Arkansas FayettevilleAR72701 United States Mechanical Engineering Department University of Kerbala Kerbala Iraq Microelectronics-Photonics Program University of Arkansas FayettevilleAR72701 United States Arktonics LLC University of Arkansas FayettevilleAR72701 United States Department of Physics Wasit University Kut Iraq Institute for Nano Science and Engineering University of Arkansas FayettevilleAR72701 United States Department of Chemistry and Physics University of Arkansas Pine Bluff Pine BluffAR71601 United States

ISBN: (纸本)9781607685395

Germanium films were deposited on silicon substrate by an ultrahigh vacuum chemical vapor deposition system using GeH4 as Ge precursor and different carrier gases (Ar, N2 and H2). Silicongermanium and SiGeSn films were deposited using optimized growth conditions of Ge growth. Silane and SnD4 were used as precursors for Si and Sn, respectively. A complete study of SiGe growth at chamber pressure from 0.1 to 1.0 torr and at temperatures from 350-450°C for different SiH4 flow rate is performed. Silicon incorporation in Ge films varied from 1% to 17%. Tin incorporation of 2% was observed in the films with 17% Si incorporation. Investigation of film quality has been done using etch pit measurement, scanning electron microscopy and transmission electron microscopy. Threading dislocation density for Ge, SiGe and SiGeSn films were 1.7×10 cm-2, 2.3 ×10 cm-2 and 4.0 ×10 cm-2, respectively. © The Electrochemical Society.

关键词： Si-Ge alloys

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Electromechanical Properties of One Dimensinal Carbon Chains

Electromechanical Properties of One Dimensinal Carbon Chains

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IEEE International Conference on Nano/Molecular Medicine and Engineering

作者： Zeina Salman Arun Nair Steve Tung Microelectronics and Photonics Graduate Program University of Arkansas Fayetteville Arkansas 72701 USA Department of Mechanical Engineering University of Arkansas Fayetteville Arkansas 72701 USA

ISBN: (纸本)9781467396738

Carbon based nanostructures such as graphene and carbon nanotubes have received widespread attention due to their unique mechanical and electronic properties. This paper describes a quantum mechanics based study of the electronic band structures and transport properties of one-dimensional (1D) carbon chains, the thinnest nanowires available in nature. The study is based on the application of density functional theory and non-equilibrium Green's function where maximally localized Wannier functions and Landauer formalism are combined to compute the electronic band structures and quantum conductance of the 1D carbon chains. The simulation result indicates that the peak quantum conductance of 1D carbon chains is about five times smaller than that of carbon nanotubes. However, the quantum conductance is also a function of the length and chemical bonds of the carbon chains. When the carbon chains are mechanically strained at 3%, the quantum conductance is reduced by about 50%. This result suggests 1D carbon chains can provide ultra high-resolution electromechanical measurements of important biomolecules such as DNA.

关键词： Carbyne Chains First-principle simulation Localized Wannier Functions Quantum Conductance

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Broadband absorptance high efficiency silicon nanowire fractal arrays for photovoltaic applications

Broadband absorptance high efficiency silicon nanowire fract...

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2014 MRS Spring Meeting

作者： Alzoubi, Omar H. Abu-Safe, Husam Alshurman, Khalid Naseem, Hameed A. Department of Electrical Engineering University of Arkansas FayettevilleAR72701 United States Natural Resources Engineering and Management German-Jordanian University Madaba Jordan Microelectronics and Photonics Program University of Arkansas FayettevilleAR72701 United States

Nanowire arrays have been proposed to enhance light trapping, increase efficiencies, and reduced material cost in photovoltaic solar cells. In this work we present a new crystalline silicon nanowire array structure, inspired by fractal geometry. The array structure is assumed to be an infinite 2D array in the x and y directions, and composed of vertically aligned SiNW suspended in air. Hexagonal fractal-like geometry is adapted in arranging cylindrical SiNW in these arrays. Full-wave finite element method 3D simulation is used to compute reflectance, transmittance and absorptance of the array for a normal incidence plane wave. The proposed fractal-like distribution of SiNW arrays yield broad absorption spectrum and enhanced efficiency while using less material. The efficiency of the proposed fractal-like SiNW arrays achieve ∼100% enhancement over that of the equivalent thickness flat c-Si film, and ∼18% enhancement over an equivalent height hexagonal array. The proposed optimized structures achieved a filling ratio ∼25%, which is ∼33% less than the corresponding hexagonal array. Copyright © 2014 Materials Research Society.

关键词： Silicon compounds

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Terahertz investigation of X-ray anti-imaging coatings: Spectroscopic characterization and imaging

Terahertz investigation of X-ray anti-imaging coatings: Spec...

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International Conference on Infrared and Millimeter Waves

作者： Nathan M. Burford Brennen Freiburger Magda El-Shenawee University of Arkansas Microelectronics-Photonics Program Fayetteville AR USA Space Photonics Inc Fayetteville AR USA Electrical Engineering Department University of Arkansas Fayetteville AR USA

An investigation of the terahertz properties of x-ray blocking and scattering (XBS) coating materials is performed. Spectral characterizations of the XBS materials reveal much stronger absorption coefficients as compared to the control coatings, as well as significant change in the refractive index. To examine the effectiveness of the coating material, pulsed THz reflection images of coated electronic microchip circuits are obtained. The microchips are covered with XBS coatings of varying thickness. The results demonstrate that this coating can successfully block the incident THz signal between 0.08 and 4 THz if the coating is sufficiently thick. This allowed for the proper thickness of the coating to be determined such that potential intellectual property contained in the microchip design could be protected from THz imaging.

关键词： Coatings Imaging Absorption Reflection X-ray imaging Additives

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Multiphysics modeling of THz photoconductive antennas

Multiphysics modeling of THz photoconductive antennas

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International Conference on Infrared and Millimeter Waves

作者： Nathan M. Burford Magda El-Shenawee University of Arkansas Microelectronics-Photonics Program Fayetteville AR USA Electrical Engineering Department University of Arkansas Fayetteville AR USA

A new method for modeling terahertz photoconductive antennas (THz-PCAs) is presented. The finite element method solver COMSOL® is utilized to combine Maxwell's, Poisson's and the Drift-Diffusion equations into a single 2D/3D multiphysics model. This model can then be used to computationally investigate and design THz-PCAs with more complex geometries compared with current numerical methods. Preliminary results show good agreement between the proposed model and the standard analytical methods for calculating photocurrent generation in THz-PCAs, as well as supporting previously reported experimental observations.

关键词： Mathematical model Optical pulses Electrodes Photoconductivity Antennas Solid modeling Equations

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Broadband Absorptance High Efficiency Silicon Nanowire Fractal Arrays for Photovoltaic Applications

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MRS Online Proceedings Library (OPL) 2014年第1期1707卷 mrss14-1707-uu06-02-mrss14-1707-uu06-02页

作者： Omar H. Alzoubi Husam Abu-Safe Khalid Alshurman Hameed A. Naseem Department of Electrical Engineering University of Arkansas Fayetteville AR 72701 U.S.A. Natural Resources Engineering and Management German-Jordanian University Madaba Jordan Microelectronics and photonics program University of Arkansas Fayetteville AR 72701 U.S.A.

关键词： photovoltaic optical nanostructure

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Optimization of nanotoroid arrays for plasmonic solar cell applications

Optimization of nanotoroid arrays for plasmonic solar cell a...

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IEEE International Symposium on Antennas and Propagation

作者： N. M. Burford M. El-Shenawee Computational Electromagnetics Group Microelectronics-Photonics Program University of Arkansas Department of Electrical Engineering University of Arkansas

ISBN: (纸本)9781467353168

This work presents the optimization of silver plasmonic nanotoroids in an infinite square array configuration located on top of an amorphous silicon substrate. Using the computational electromagnetics software Ansys HFSS, the electromagnetic energy absorption enhancement in the silicon layer is optimized by varying the geometric configuration. Percentage enhancement of the generated photocurrent is approximated and is used to compare the performance of various nanotoroid designs, as well as comparison to other geometries.

关键词： program unit solar cells Geometric forms Computational electromagnetics Electromagnetic Energies arrays Refractive surgery enhancement amorphous silicon

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