Formation of SiNx:H by PECVD: optimization of the optical, bulk passivation and structural properties for photovoltaic applications

International Nuclear Information System (INIS)

Lelievre, J.F.

2007-04-01

The hydrogenated silicon nitride SiNx:H is widely used as antireflection coating and passivation layer in the manufacture of silicon photovoltaic cells. The aim of this work was to implement a low frequency (440 kHz) PECVD reactor and to characterize the obtained SiN layers. After having determined the parameters of the optimal deposition, the physico-chemical structure of the layers has been studied. The optical properties have been studied with the aim to improve the antireflection coating of the photovoltaic cells. The surface and bulk passivation properties, induced by the SiN layer in terms of its stoichiometry, have been analyzed and have revealed the excellent passivating efficiency of this material. At last, have been studied the formation conditions of the silicon nano-crystals in the SiN matrix. (O.M.)

Optical and electronic properties of 2 H -Mo S2 under pressure: Revealing the spin-polarized nature of bulk electronic bands

Science.gov (United States)

Brotons-Gisbert, Mauro; Segura, Alfredo; Robles, Roberto; Canadell, Enric; Ordejón, Pablo; Sánchez-Royo, Juan F.

2018-05-01

Monolayers of transition-metal dichalcogenide semiconductors present spin-valley locked electronic bands, a property with applications in valleytronics and spintronics that is usually believed to be absent in their centrosymmetric (as the bilayer or bulk) counterparts. Here we show that bulk 2 H -Mo S2 hides a spin-polarized nature of states determining its direct band gap, with the spin sequence of valence and conduction bands expected for its single layer. This relevant finding is attained by investigating the behavior of the binding energy of A and B excitons under high pressure, by means of absorption measurements and density-functional-theory calculations. These results raise an unusual situation in which bright and dark exciton degeneracy is naturally broken in a centrosymmetric material. Additionally, the phonon-assisted scattering process of excitons has been studied by analyzing the pressure dependence of the linewidth of discrete excitons observed at the absorption coefficient edge of 2 H -Mo S2 . Also, the pressure dependence of the indirect optical transitions of bulk 2 H -Mo S2 has been analyzed by absorption measurements and density-functional-theory calculations. These results reflect a progressive closure of the indirect band gap as pressure increases, indicating that metallization of bulk Mo S2 may occur at pressures higher than 26 GPa.

Investigation of optical properties and electronic transitions in bulk and nano-microribbons of molybdenum trioxide

International Nuclear Information System (INIS)

Lupan, O; Mishra, Y K; Adelung, R; Trofim, V; Cretu, V; Stamov, I; Syrbu, N N; Tiginyanu, I

2014-01-01

In this work, we report on crystalline quality and optical characteristics of molybdenum trioxide (MoO 3 ) bulk and nano-microribbons grown by rapid thermal oxidation (RTO). The developed RTO procedure allows one to synthesize highly crystalline (α-phase) bulk and nano-microribbons of MoO 3 . For R–Γ indirect transitions in bulk single crystals of MoO 3 , it has been found that the width of the bandgap along the E‖c polarization, associated with transitions R v1 –Γ c1 , is lower than the width of the band gap in polarization E ⊥ c, associated with transitions R v2 –Γ c2 . This result is indicative of splitting of the absorption edge due to α-MoO 3 structural anisotropy. Studies of the polarization dependence of the absorption in nano-microribbons (d ≈ 15–500 nm) demonstrated that the energy gap corresponding to R v1 –X c1 (E‖c) transition is smaller than that of R v2 –X c2 (E ⊥ c) transition. Similar dependence has been found for the R–Y indirect transitions. The results of the investigation of the reflectance spectra in the energy range from 3 to 6 eV are shown. By using the Kramers–Kronig method, the optical functions were derived from the reflection spectra of nano-microribbons, and the polarization dependence of direct energy transitions at the point R in the Brillouin zone are determined. The alternation in splitting caused by polarization of the absorption edge related to indirect transitions due to polarization opens new prospects for the design and fabricating interesting optoelectronic devices based on α-MoO 3 bulk and nano-microribbons with characteristics dependent on the polarization of light waves. (paper)

OPTICAL AND DYNAMIC PROPERTIES OF UNDOPED AND DOPED SEMICONDUCTOR NANOSTRUCTURES

Energy Technology Data Exchange (ETDEWEB)

Grant, C D; Zhang, J Z

2007-09-28

This chapter provides an overview of some recent research activities on the study of optical and dynamic properties of semiconductor nanomaterials. The emphasis is on unique aspects of these properties in nanostructures as compared to bulk materials. Linear, including absorption and luminescence, and nonlinear optical as well as dynamic properties of semiconductor nanoparticles are discussed with focus on their dependence on particle size, shape, and surface characteristics. Both doped and undoped semiconductor nanomaterials are highlighted and contrasted to illustrate the use of doping to effectively alter and probe nanomaterial properties. Some emerging applications of optical nanomaterials are discussed towards the end of the chapter, including solar energy conversion, optical sensing of chemicals and biochemicals, solid state lighting, photocatalysis, and photoelectrochemistry.

Thermo-optical properties of residential coals and combustion aerosols

Science.gov (United States)

Pintér, Máté; Ajtai, Tibor; Kiss-Albert, Gergely; Kiss, Diána; Utry, Noémi; Janovszky, Patrik; Palásti, Dávid; Smausz, Tomi; Kohut, Attila; Hopp, Béla; Galbács, Gábor; Kukovecz, Ákos; Kónya, Zoltán; Szabó, Gábor; Bozóki, Zoltán

2018-04-01

In this study, we present the inherent optical properties of carbonaceous aerosols generated from various coals (hard through bituminous to lignite) and their correlation with the thermochemical and energetic properties of the bulk coal samples. The nanoablation method provided a unique opportunity for the comprehensive investigation of the generated particles under well controlled laboratory circumstances. First, the wavelength dependent radiative features (optical absorption and scattering) and the size distribution (SD) of the generated particulate matter were measured in-situ in aerosol phase using in-house developed and customised state-of-the-art instrumentation. We also investigated the morphology and microstructure of the generated particles using Transmission Electron Microscopy (TEM) and Electron Diffraction (ED). The absorption spectra of the measured samples (quantified by Absorption Angström Exponent (AAE)) were observed to be distinctive. The correlation between the thermochemical features of bulk coal samples (fixed carbon (FC) to volatile matter (VM) ratio and calorific value (CV)) and the AAE of aerosol assembly were found to be (r2 = 0.97 and r2 = 0.97) respectively. Lignite was off the fitted curves in both cases most probably due to its high optically inactive volatile material content. Although more samples are necessary to be investigated to draw statistically relevant conclusion, the revealed correlation between CV and Single Scattering Albedo (SSA) implies that climatic impact of coal combusted aerosol could depend on the thermal and energetic properties of the bulk material.

Optical and terahertz measurement techniques for flat-faced pharmaceutical tablets: a case study of gloss, surface roughness and bulk properties of starch acetate tablets

International Nuclear Information System (INIS)

Juuti, M; Tuononen, H; Kontturi, V; Peiponen, K-E; Prykäri, T; Alarousu, E; Myllylä, R; Kuosmanen, M; Ketolainen, J

2009-01-01

Surface and bulk properties of flat-faced starch acetate tablets were studied. For surface quality inspection optical coherence tomography and recently developed diffractive glossmeter were utilized. Both these optical devices together provide local information on surface roughness and gloss of a tablet over a measured area. The concepts of mean topography and mean gloss profile for surface quality of a tablet are introduced. It was observed that the surface quality of the tablet varies, and compression at high pressure may not guarantee a good surface quality of the tablet. Using novel statistical parameters for gloss and relevant surface roughness parameter, it is possible to get more comprehensive quantitative data on the surface condition of a tablet. THz spectrometer was utilized for detection of THz pulse delay in transmission measurement mode from the tablets. The delay time and thickness ratio of the tablet are consistent with the porosity of the tablet as a function of compression pressure. We suggest that the multimeasurement scheme using three different devices helps tablet makers to better assess bulk and surface quality of their products

Electronic and optical properties of graphene-like InAs: An ab initio study

Science.gov (United States)

Sohrabi, Leila; Boochani, Arash; Ali Sebt, S.; Mohammad Elahi, S.

2018-03-01

The present work initially investigates structural, optical, and electronic properties of graphene-like InAs by using the full potential linear augmented plane wave method in the framework of density functional theory and is then compared with the bulk Indium Arsenide in the wurtzite phase. The lattice parameters are optimized with GGA-PBE and LDA approximations for both 2D- and 3D-InAs. In order to study the electronic properties of graphene-like InAs and bulk InAs in the wurtzite phase, the band gap is calculated by GGA-PBG and GGA-EV approximations. Moreover, optical parameters of graphene-like InAs and bulk InAs such as the real and imaginary parts of dielectric function, electron energy loss function, refractivity, extinction and absorption coefficients, and optical conductivity are investigated. Plasmonic frequencies of 2D- and 3D-InAs are also calculated by using maximum electron energy loss function and the roots of the real part of the dielectric function.

Improved ice particle optical property simulations in the ultraviolet to far-infrared regime

International Nuclear Information System (INIS)

Bi, Lei; Yang, Ping

2017-01-01

To derive the bulk radiative properties of ice clouds, aircraft contrails and snow grains, which are fundamental to atmospheric radiative transfer calculations in downstream applications, it is necessary to accurately simulate the scattering of light by individual ice particles. An ice particle optical property database reported in 2013 (hereafter, TAMUice2013) is updated (hereafter, TAMUice2016) to incorporate recent advances in computation of the optical properties of nonspherical particles. Specifically, we employ the invariant imbedding T-matrix (II-TM) method to compute the optical properties of particles with small to moderate size parameters. Both versions use the Improved Geometric Optics Method (IGOM) to compute the optical properties of large ice crystals, but TAMUice2016 improves the treatment of inhomogeneous waves inside the scattering particles in the case where ice is absorptive such as at infrared wavelengths. To bridge the gap between the extinction efficiencies computed from the II-TM and the IGOM, TAMUice2016 includes spectrally dependent higher order terms of the edge effect in addition to the first order counterpart considered in TAMUice2013. Furthermore, the differences between TAMUice2013 and TAMUice2016 are quantified with respect to the computation of the bulk optical properties of ice clouds. - Highlights: • A previous database of the single-scattering properties of ice crystals is improved. • A combination of the invariant imbedding T-matrix and improved geometric optics methods is used. • The treatment of inhomogeneous waves in an absorptive ice crystal is improved. • Higher order terms of the edge effect are considered in the updated database.

Bulk and Thin film Properties of Nanoparticle-based Ionic Materials

Science.gov (United States)

Fang, Jason

2008-03-01

Nanoparticle-based ionic materials (NIMS) offer exciting opportunities for research at the forefront of science and engineering. NIMS are hybrid particles comprised of a charged oligomeric corona attached to hard, inorganic nanoparticle cores. Because of their hybrid nature, physical properties --rheological, optical, electrical, thermal - of NIMS can be tailored over an unusually wide range by varying geometric and chemical characteristics of the core and canopy and thermodynamic variables such as temperature and volume fraction. On one end of the spectrum are materials with a high core content, which display properties similar to crystalline solids, stiff waxes, and gels. At the opposite extreme are systems that spontaneously form particle-based fluids characterized by transport properties remarkably similar to simple liquids. In this poster I will present our efforts to synthesize NIMS and discuss their bulk and surface properties. In particular I will discuss our work on preparing smart surfaces using NIMS.

Theoretical approach to embed nanocrystallites into a bulk crystalline matrix and the embedding influence on the electronic band structure and optical properties of the resulting heterostructures.

Science.gov (United States)

Balagan, Semyon Anatolyevich; Nazarov, Vladimir U; Shevlyagin, Alexander Vladimirovich; Goroshko, Dmitrii L; Galkin, N G

2018-05-03

We develop an approach and present results of the combined molecular dynamics and density functional theory calculations of the structural and optical properties of the nanometer-sized crystallites embedded in a bulk crystalline matrix. The method is designed and implemented for both compatible and incompatible lattices of the nanocrystallite (NC) and the host matrix, when determining the NC optimal orientation relative to the matrix constitutes a challenging problem. We suggest and substantiate an expression for the cost function of the search algorithm, which is the energy per supercell generalized for varying number of atoms in the latter. The epitaxial relationships at the Si/NC interfaces and the optical properties are obtained and found to be in a reasonable agreement with experimental data. Dielectric functions show significant sensitivity to the NC's orientation relative to the matrix at energies below 0.5 eV. © 2018 IOP Publishing Ltd.

Theoretical approach to embed nanocrystallites into a bulk crystalline matrix and the embedding influence on the electronic band structure and optical properties of the resulting heterostructures

Science.gov (United States)

Balagan, Semyon A.; Nazarov, Vladimir U.; Shevlyagin, Alexander V.; Goroshko, Dmitrii L.; Galkin, Nikolay G.

2018-06-01

We develop an approach and present results of the combined molecular dynamics and density functional theory calculations of the structural and optical properties of the nanometer-sized crystallites embedded in a bulk crystalline matrix. The method is designed and implemented for both compatible and incompatible lattices of the nanocrystallite (NC) and the host matrix, when determining the NC optimal orientation relative to the matrix constitutes a challenging problem. We suggest and substantiate an expression for the cost function of the search algorithm, which is the energy per supercell generalized for varying number of atoms in the latter. The epitaxial relationships at the Si/NC interfaces and the optical properties are obtained and found to be in a reasonable agreement with experimental data. Dielectric functions show significant sensitivity to the NC’s orientation relative to the matrix at energies below 0.5 eV.

Optical properties of likely constituents of interstellar dust

International Nuclear Information System (INIS)

Dayawansa, I.J.

1977-07-01

Optical properties of polyoxymethylene (POM) at room temperature have been measured from the near ultra-violet to infrared as an initial stage of a link between interstellar dust and organic matter, and the results, which are particularly relevant to interstellar extinction, are reported. There is a strong possibility of a more complex organic component which could significantly contribute to the interstellar extinction. Measurements have also been made of the effect of fast neutron bombardment on the optical properties of quartz (SiO 2 ). At a high total flux of neutrons the crystalline quartz will change to its amorphous form which has extinction properties that resemble the interstellar extinction. Extinction due to small particles of several forms of SiO 2 has been measured and among them the hydrated mineral, opal, behaved like an amorphous silica. Neutron irradiated olivine showed a stronger and a broader 10μm band in addition to weaker bands towards the longer wavelengths which indicated that atomic damage has been produced. At high fluxes more atomic damage is expected to change the crystalline structure and thereby cause changes in the infrared absorption properties. Extinction measurements were also made for smoke particles of MgO in the infrared. When the measurements were made with the particles deposited on substrates, in addition to a very broad surface mode absorption feature around 20μm an extinction maximum was observed typical of the bulk mode at 25μm. Extinction measurements for MgO smoke particles in air also showed similar results. However when the particles were dispersed in a non-absorbing medium, the bulk absorption mode was not observed. This implies that the appearance of the bulk mode is due to clumping. (author)

Thermophysical and Optical Properties of Semiconducting Ga2Te3 Melt

Science.gov (United States)

Li, Chao; Su, Ching-Hua; Lehoczky, Sandor L.; Scripa, Rosalie N.; Ban, Heng

2005-01-01

The majority of bulk semiconductor single crystals are presently grown from their melts. The thermophysical and optical properties of the melts provide a fundamental understanding of the melt structure and can be used to optimize the growth conditions to obtain higher quality crystals. In this paper, we report several thermophysical and optical properties for Ga2Te3 melts, such as electrical conductivity, viscosity, and optical transmission for temperatures ranging from the melting point up to approximately 990 C. The conductivity and viscosity of the melts are determined using the transient torque technique. The optical transmission of the melts is measured between the wavelengths of 300 and 2000 nm by an dual beam reversed-optics spectrophotometer. The measured properties are in good agreement with the published data. The conductivities indicate that the Ga2Te3 melt is semiconductor-like. The anomalous behavior in the measured properties are used as an indication of a structural transformation in the Ga2Te3 melt and discussed in terms of Eyring's and Bachinskii's predicted behaviors for homogeneous melts.

Investigations on growth morphology, bulk growth and crystalline perfection of L-threonine, an organic nonlinear optical material

International Nuclear Information System (INIS)

Linet, J. Mary; Das, S. Jerome

2010-01-01

L-threonine single crystal was successfully grown from aqueous solution. The morphology of the grown crystal was compared with the predicted morphology using Bravais-Friedel-Donnay-Harker law and was found to be in good agreement with the predicted morphology. Good optical quality bulk single crystal of enhanced size has been grown using unidirectional crystal growth method. High-resolution X-ray analysis study resulted in a rocking curve with a full width half maximum of 20 arc sec exhibiting the good crystalline quality of the grown crystal. The optical transmission study shows 90% of transmission in the entire visible region that exhibits the good optical quality of the grown crystal. The mechanical properties were analyzed by Vicker's microhardness method.

Characterization and bulk properties of oxides

International Nuclear Information System (INIS)

Sonder, E.; Connolly, T.F.

1979-06-01

The bulk properties of oxides are divided into two classes, intrinsic properties which depend solely on the identity of the material, and extrinsic ones, which differ for different samples of the same compound. Sources of tabulated numerical values of intrinsic properties are given and modern developments in information storage and retrieval are discussed. Extrinsic properties are shown to depend on defects and trace impurities in the samples. Techniques of trace impurity analysis are discussed and realistic limits of detection and accuracies are given for routine analyses

Spark plasma sintering of bulk SrAl2O4-Sr3Al2O6 eutectic glass with wide-band optical window

Science.gov (United States)

Liu, Jiaxi; Lu, Nan; He, Gang; Li, Xiaoyu; Li, Jianqiang; Li, Jiangtao

2018-06-01

SrAl2O4-Sr3Al2O6 eutectic glass was prepared by using an aerodynamic levitator equipped with a CO2 laser device. A bulk transparent amorphous sample was obtained by the spark plasma sintering (SPS) of the prepared eutectic glass. XRD, a UV–vis-NIR spectrophotometer and FT-IR were employed to characterize the phase evolution and optical properties. The results show that the bulk SrAl2O4-Sr3Al2O6 samples fabricated by the containerless process and SPS between 852 °C–857 °C were fully amorphous. The amorphous sample has a wide transparent window between 270 nm and 6.2 μm. The average refractive index in the visible light region is 1.680 and the Abbe number is 27.4. The prepared bulk SrAl2O4-Sr3Al2O6 eutectic glass with the wide-band optical window may be a promising candidate for optical applications.

Electro-optical modeling of bulk heterojunction solar cells

Science.gov (United States)

Kirchartz, Thomas; Pieters, Bart E.; Taretto, Kurt; Rau, Uwe

2008-11-01

We introduce a model for charge separation in bulk heterojunction solar cells that combines exciton transport to the interface between donor and acceptor phases with the dissociation of the bound electron/hole pair. We implement this model into a standard semiconductor device simulator, thereby creating a convenient method to simulate the optical and electrical characteristics of a bulk heterojunction solar cell with a commercially available program. By taking into account different collection probabilities for the excitons in the polymer and the fullerene, we are able to reproduce absorptance, internal and external quantum efficiency, as well as current/voltage curves of bulk heterojunction solar cells. We further investigate the influence of mobilities of the free excitons as well as the mobilities of the free charge carriers on the performance of bulk heterojunction solar cells. We find that, in general, the highest efficiencies are achieved with the highest mobilities. However, an optimum finite mobility of free charge carriers can result from a large recombination velocity at the contacts. In contrast, Langevin-type of recombination cannot lead to finite optimum mobilities even though this mechanism has a strong dependence on the free carrier mobilities.

The applicability of physical optics in the millimetre and sub-millimetre spectral region. Part II: Application to a three-component model of ice cloud and its evaluation against the bulk single-scattering properties of various other aggregate models

Science.gov (United States)

Baran, Anthony J.; Ishimoto, Hiroshi; Sourdeval, Odran; Hesse, Evelyn; Harlow, Chawn

2018-02-01

The bulk single-scattering properties of various randomly oriented aggregate ice crystal models are compared and contrasted at a number of frequencies between 89 and 874 GHz. The model ice particles consist of the ten-branched plate aggregate, five-branched plate aggregate, eight-branched hexagonal aggregate, Voronoi ice aggregate, six-branched hollow bullet rosette, hexagonal column of aspect ratio unity, and the ten-branched hexagonal aggregate. The bulk single-scattering properties of the latter two ice particle models have been calculated using the light scattering methods described in Part I, which represent the two most extreme members of an ensemble model of cirrus ice crystals. In Part I, it was shown that the method of physical optics could be combined with the T-matrix at a size parameter of about 18 to compute the bulk integral ice optical properties and the phase function in the microwave to sufficient accuracy to be of practical value. Here, the bulk single-scattering properties predicted by the two ensemble model members and the Voronoi model are shown to generally bound those of all other models at frequencies between 89 and 874 GHz, thus representing a three-component model of ice cloud that can be generally applied to the microwave, rather than using many differing ice particle models. Moreover, the Voronoi model and hollow bullet rosette scatter similarly to each other in the microwave. Furthermore, from the various comparisons, the importance of assumed shapes of the particle size distribution as well as cm-sized ice aggregates is demonstrated.

Properties of Bulk Sintered Silver As a Function of Porosity

Energy Technology Data Exchange (ETDEWEB)

Wereszczak, Andrew A [ORNL; Vuono, Daniel J [ORNL; Wang, Hsin [ORNL; Ferber, Mattison K [ORNL; Liang, Zhenxian [ORNL

2012-06-01

This report summarizes a study where various properties of bulk-sintered silver were investigated over a range of porosity. This work was conducted within the National Transportation Research Center's Power Device Packaging project that is part of the DOE Vehicle Technologies Advanced Power Electronics and Electric Motors Program. Sintered silver, as an interconnect material in power electronics, inherently has porosity in its produced structure because of the way it is made. Therefore, interest existed in this study to examine if that porosity affected electrical properties, thermal properties, and mechanical properties because any dependencies could affect the intended function (e.g., thermal transfer, mechanical stress relief, etc.) or reliability of that interconnect layer and alter how its performance is modeled. Disks of bulk-sintered silver were fabricated using different starting silver pastes and different sintering conditions to promote different amounts of porosity. Test coupons were harvested out of the disks to measure electrical resistivity and electrical conductivity, thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, and yield stress. The authors fully recognize that the microstructure of processed bulk silver coupons may indeed not be identical to the microstructure produced in thin (20-50 microns) layers of sintered silver. However, measuring these same properties with such a thin actual structure is very difficult, requires very specialized specimen preparation and unique testing instrumentation, is expensive, and has experimental shortfalls of its own, so the authors concluded that the herein measured responses using processed bulk sintered silver coupons would be sufficient to determine acceptable values of those properties. Almost all the investigated properties of bulk sintered silver changed with porosity content within a range of 3-38% porosity. Electrical resistivity, electrical conductivity

Structural and optical properties of CdSe nanosheets

Science.gov (United States)

Solanki, Rekha Garg; Rajaram, P.; Arora, Aman

2018-04-01

Nanosheets of CdSe have been synthesized using a solvothermal route using citric acid as an additive. It is found that the citric acid effectively controls the structural and optical properties of CdSe nanostructures. XRD studies confirm the formation of hexagonal wurtzite phase of CdSe. The FESEM micrographs show that the obtained CdSe nanocrystals are in the form of very thin sheets (nanosheets). Optical absorption studies as well as Photoluminescence spectra show that the optical gap is around 1.76 eV which is close to the reported bulk value of 1.74 eV. The prepared CdSe nanosheets because of large surface area may be useful for catalytic activities in medicine, biotechnology and environmental chemistry and in biomedical imaging for in vitro detection of a breast cancer cells.

Quantum Electrostatic Model for Optical Properties of Nanoscale Gold Films

Directory of Open Access Journals (Sweden)

Qian Haoliang

2015-11-01

Full Text Available The optical properties of thin gold films with thickness varying from 2.5 nm to 30 nm are investigated. Due to the quantum size effect, the optical constants of the thin gold film deviate from the Drude model for bulk material as film thickness decreases, especially around 2.5 nm, where the electron energy level becomes discrete. A theory based on the self-consistent solution of the Schrödinger equation and the Poisson equation is proposed and its predictions agree well with experimental results.

Anionic or Cationic S-Doping in Bulk Anatase TiO 2 : Insights on Optical Absorption from First Principles Calculations

KAUST Repository

Harb, Moussab

2013-05-02

Using first principles calculations, we investigate the structural, electronic, optical, and energetic properties of S-doped anatase TiO2 bulk systems. To ensure accurate band gap predictions, we use the HSE06 exchange correlation functional, and the absorption spectra are obtained with density functional perturbation (DFPT) theory by employing HSE06. Various oxidation states (anionic and cationic) of sulfur are considered depending on the location in bulk TiO2: in interstitial position or in substitution for either oxygen or titanium atoms. Among the explored structures, two anionic and one cationic configurations induce an improved optical absorption response in the visible region as observed experimentally. Moreover, we undertake a thermodynamic analysis as a function of the chemical potential of oxygen and considering three relevant sulfur chemical doping agents (S 2, H2S, and thiourea). It highlights that cationic configurations (S4+ and S6+) are strongly stabilized in a wide range of oxygen chemical potential (including standard conditions), whereas anionic species are stabilized only at very low chemical potential of oxygen. The metastable cationic Ti(1-2x)O2S2x system involving the presence of S4+ species in substitution for Ti 4+, with the formation of SO2 units, should offer the best compromise between the thermodynamic conditions and the expected optical properties. © 2013 American Chemical Society.

Optical bulk and surface waves with negative refraction

International Nuclear Information System (INIS)

Agranovich, V.M.; Shen, Y.R.; Baughman, R.H.; Zakhidov, A.A.

2004-01-01

In materials with negative refraction, the direction of wave propagation is opposite to the direction of the wave vector. Using an approach that characterizes the optical response of a medium totally by a generalized dielectric permittivity, ε-bar (ω,k-bar), we discuss the possibility of seeing negative refraction for optical waves in a number of nonmagnetic media. These include bulk waves in organic materials and in gyrotropic materials where additional exciton-polariton waves can have a negative group velocity. It is known that dispersion of surface waves can be engineered by tailoring a surface transition layer. We show how this effect can be used to obtain surface waves with negative refraction

Correlated structure-optical properties studies of plasmonic nanoparticles

International Nuclear Information System (INIS)

Ringe, Emilie; Duyne, Richard P Van; Marks, Laurence D

2014-01-01

Interest in nanotechnology is driven by unprecedented means to tailor the physical behaviour via structure and composition. Unlike bulk materials, minute changes in size and shape can affect the optical properties of nanoparticles. Characterization, understanding, and prediction of such structure-function relationships is crucial to the development of novel applications such as plasmonic sensors, devices, and drug delivery systems. Such knowledge has been recently vastly expanded through systematic, high throughput correlated measurements, where the localized surface plasmon resonance (LSPR) is probed optically and the particle shape investigated with electron microscopy. This paper will address some of the recent experimental advances in single particle studies that provide new insight not only on the effects of size, composition, and shape on plasmonic properties but also their interrelation. Plasmon resonance frequency and decay, substrate effects, size, shape, and composition will be explored for a variety of plasmonic systems

Electronic properties and optical absorption of a phosphorene quantum dot

Science.gov (United States)

Liang, F. X.; Ren, Y. H.; Zhang, X. D.; Jiang, Z. T.

2018-03-01

Using the tight-binding Hamiltonian approach, we theoretically study the electronic and optical properties of a triangular phosphorene quantum dot (PQD) including one normal zigzag edge and two skewed armchair edges (ZAA-PQD). It is shown that the energy spectrum can be classified into the filled band (FB), the zero-energy band (ZB), and the unfilled band (UB). Numerical calculations of the FB, ZB, and UB probability distributions show that the FB and the UB correspond to the bulk states, while the ZB corresponds to the edge states, which appear on all of the three edges of the ZAA-PQD sharply different from the other PQDs. We also find that the strains and the electric fields can affect the energy levels inhomogeneously. Then the optical properties of the ZAA-PQD are investigated. There appear some strong low-energy optical absorption peaks indicating its sensitive low-energy optical response that is absent in other PQDs. Moreover, the strains and the electric fields can make inhomogeneous influences on the optical spectrum of the ZAA-PQD. This work may provide a useful reference for designing the electrical, mechanical, and optical PQD devices.

Crystallinity and flux pinning properties of MgB2 bulks

International Nuclear Information System (INIS)

Yamamoto, A.; Shimoyama, J.; Ueda, S.; Katsura, Y.; Iwayama, I.; Horii, S.; Kishio, K.

2006-01-01

The relationship between flux pinning properties and crystallinity of MgB 2 bulks was systematically studied. Improved flux pinning properties under high fields were observed for samples with low crystallinity. Increased impurity scattering due to strain and defects in lattice corresponding to the degraded crystallinity was considered to enhance flux pinning strength at grain boundaries. Low-temperature synthesis and carbon substitution were confirmed to be effective for degrading crystallinity of MgB 2 bulks, resulting in high critical current properties under high fields

High temperature superconductor bulk materials. Fundamentals - processing - properties control - application aspects

International Nuclear Information System (INIS)

Krabbes, G.; Fuchs, G.; Canders, W.R.; May, H.; Palka, R.

2006-01-01

This book presents all the features of bulk high temperature superconducting materials. Starting from physical and chemical fundamentals, the authors move on to portray methods and problems of materials processing, thoroughly working out the characteristic properties of bulk superconductors in contrast to long conductors and films. The authors provide a wide range of specific materials characteristics with respect to the latest developments and future applications guiding from fundamentals to practical engineering examples. This book contains the following chapters: 1. Fundamentals 2. Growth and melt processing of YBCO 3. Pinning-relevant defects in bulk YBCO 4. Properties of bulk YBCO 5. Trapped fields 6. Improved YBCO based bulk superconductors and functional elements 7. Alternative systems 8. Peak effect 9. Very high trapped fields in YBCO permanent magnets 10. Engineering aspects: Field distribution in bulk HTSC 11. Inherently stable superconducting magnetic bearings 12. Application of bulk HTSCs in electromagnetic energy converters 13. Applications in magnet technologies and power supplies

Study of optical properties of Erbium doped Tellurite glass-polymer composite

Science.gov (United States)

Sushama, D.

2014-10-01

Chalcogenide glasses have wide applications in optical device technology. But it has some disadvantages like thermal instability. Among them Tellurite glasses exhibits high thermal Stability. Doping of rare earth elements into the Tellurite glasses improve its optical properties. To improve its mechanical properties composites of this Tellurite glasses with polymer are prepared. Bulk samples of Er2O3 doped TeO2-WO3-La2O3 Tellurite glasses are prepared from high purity oxide mixtures, melting in an alumina crucible in air atmosphere. Composites of this Tellurite glasses with polymer are prepared by powder mixing method and the thin films of these composites are prepared using polymer press. Variations in band gap of these composites are studied from the UV/Vis/NIR absorption.

Structure and physical properties of silicon clusters and of vacancy clusters in bulk silicon

International Nuclear Information System (INIS)

Sieck, A.

2000-01-01

In this thesis the growth-pattern of free silicon clusters and vacancy clusters in bulk silicon is investigated. The aim is to describe and to better understand the cluster to bulk transition. Silicon structures in between clusters and solids feature new interesting physical properties. The structure and physical properties of silicon clusters can be revealed by a combination of theory and experiment, only. Low-energy clusters are determined with different optimization techniques and a density-functional based tight-binding method. Additionally, infrared and Raman spectra, and polarizabilities calculated within self-consistent field density-functional theory are provided for the smaller clusters. For clusters with 25 to 35 atoms an analysis of the shape of the clusters and the related mobilities in a buffer gas is given. Finally, the clusters observed in low-temperature experiments are identified via the best match between calculated properties and experimental data. Silicon clusters with 10 to 15 atoms have a tricapped trigonal prism as a common subunit. Clusters with up to about 25 atoms follow a prolate growth-path. In the range from 24 to 30 atoms the geometry of the clusters undergoes a transition towards compact spherical structures. Low-energy clusters with up to 240 atoms feature a bonding pattern strikingly different from the tetrahedral bonding in the solid. It follows that structures with dimensions of several Angstroem have electrical and optical properties different from the solid. The calculated stabilities and positron-lifetimes of vacancy clusters in bulk silicon indicate the positron-lifetimes of about 435 ps detected in irradiated silicon to be related to clusters of 9 or 10 vacancies. The vacancies in these clusters form neighboring hexa-rings and, therefore, minimize the number of dangling bonds. (orig.)

Optical properties of titanium trisulphide (TiS3) thin films

International Nuclear Information System (INIS)

Ferrer, I.J.; Ares, J.R.; Clamagirand, J.M.; Barawi, M.; Sánchez, C.

2013-01-01

Titanium trisulphide thin films have been grown on quartz substrates by sulphuration of electron-beam evaporated Ti layers (d ∼ 300 nm) in a vacuum sealed ampoule in the presence of sulphur powder at 550 °C for different periods of time (1 to 20 h). Thin films were characterized by X-ray diffraction, energy dispersive analyses of X-ray and scanning electron microscopy. Results demonstrate that films are composed by monoclinic titanium trisulphide. Films show n-type conductivity with a relatively high resistivity (ρ ∼ 4 ± 2 Ω·cm) and high values of the Seebeck coefficient (− 600 μV/K) at room temperature. Values of the optical absorption coefficient about α ∼ 10 5 cm −1 , determined from reflectance and transmittance measurements, have been obtained at photon energies hυ > 2 eV. The absorption coefficient dependence on the photon energy in the range of 1.6–3.0 eV hints the existence of a direct transition with an energy gap between 1.35 and 1.50 eV. By comparing these results with those obtained from bulk TiS 3 , a direct transition with lower energy is also found which could have been hidden due to the low value of the absorption coefficient in this energy range. - Highlights: ► Thin films of TiS 3 have been obtained by sulphuration of Ti layers. ► Optical properties of TiS 3 thin films have been determined. ► Optical energy gap of TiS 3 has been obtained. ► Optical properties of bulk TiS 3 have been measured and compared with those of films

Effect of Bulk and Interfacial Rheological Properties on Bubble Dissolution

NARCIS (Netherlands)

Kloek, W.; Vliet, van T.; Meinders, M.

2001-01-01

This paper describes theoretical calculations of the combined effect of bulk and interracial rheological properties on dissolution behavior of a bubble in an infinite medium at saturated conditions. Either bulk or interracial elasticity can stop the bubble dissolution process, and stability criteria

Soft magnetic properties of bulk amorphous Co-based samples

International Nuclear Information System (INIS)

Fuezer, J.; Bednarcik, J.; Kollar, P.

2006-01-01

Ball milling of melt-spun ribbons and subsequent compaction of the resulting powders in the supercooled liquid region were used to prepare disc shaped bulk amorphous Co-based samples. The several bulk samples have been prepared by hot compaction with subsequent heat treatment (500 deg C - 575 deg C). The influence of the consolidation temperature and follow-up heat treatment on the magnetic properties of bulk samples was investigated. The final heat treatment leads to decrease of the coercivity to the value between the 7.5 to 9 A/m (Authors)

3D printing of optical materials: an investigation of the microscopic properties

Science.gov (United States)

Persano, Luana; Cardarelli, Francesco; Arinstein, Arkadii; Uttiya, Sureeporn; Zussman, Eyal; Pisignano, Dario; Camposeo, Andrea

2018-02-01

3D printing technologies are currently enabling the fabrication of objects with complex architectures and tailored properties. In such framework, the production of 3D optical structures, which are typically based on optical transparent matrices, optionally doped with active molecular compounds and nanoparticles, is still limited by the poor uniformity of the printed structures. Both bulk inhomogeneities and surface roughness of the printed structures can negatively affect the propagation of light in 3D printed optical components. Here we investigate photopolymerization-based printing processes by laser confocal microscopy. The experimental method we developed allows the printing process to be investigated in-situ, with microscale spatial resolution, and in real-time. The modelling of the photo-polymerization kinetics allows the different polymerization regimes to be investigated and the influence of process variables to be rationalized. In addition, the origin of the factors limiting light propagation in printed materials are rationalized, with the aim of envisaging effective experimental strategies to improve optical properties of printed materials.

An empirical method to estimate bulk particulate refractive index for ocean satellite applications

Digital Repository Service at National Institute of Oceanography (India)

Suresh, T.; Desa, E.; Mascarenhas, A.A.M.Q.; Matondkar, S.G.P.; Naik, P.; Nayak, S.R.

An empirical method is presented here to estimates bulk particulate refractive index using the measured inherent and apparent optical properties from the various waters types of the Arabian Sea. The empirical model, where the bulk refractive index...

Austenitic stainless steel bulk property considerations for fusion reactors

International Nuclear Information System (INIS)

Mattas, R.F.

1979-04-01

The bulk properties of annealed 304, 316, and 20% cold-worked 316 stainless steels are evaluated for the temperature and radiation conditions expected in a near-term fusion reactor. Of interest are the thermophysical properties, void swelling produced by neutron radiaion, and the tensile, creep, and fatigue properties before and after irradiation

Synthesis and magnetic properties of bulk transparent PMMA/Fe-oxide nanocomposites

Science.gov (United States)

Li, Shanghua; Qin, Jian; Fornara, Andrea; Toprak, Muhammet; Muhammed, Mamoun; Kim, Do Kyung

2009-05-01

PMMA/Fe-oxide nanocomposites are fabricated by a chemical method. Monodispersed Fe-oxide nanoparticles are well dispersed in the PMMA matrix by in situ polymerization, resulting in a bulk transparent polymeric nanocomposite. The magnetic behavior of the PMMA/Fe-oxide nanocomposites is investigated. The transparent PMMA/Fe-oxide nanocomposite has potentially interesting magneto-optic applications without compromising the advantages of a lightweight, noncorrosive polymeric material with very high transparency even for bulk samples.

Synthesis and magnetic properties of bulk transparent PMMA/Fe-oxide nanocomposites

International Nuclear Information System (INIS)

Li Shanghua; Qin Jian; Fornara, Andrea; Toprak, Muhammet; Muhammed, Mamoun; Kim, Do Kyung

2009-01-01

PMMA/Fe-oxide nanocomposites are fabricated by a chemical method. Monodispersed Fe-oxide nanoparticles are well dispersed in the PMMA matrix by in situ polymerization, resulting in a bulk transparent polymeric nanocomposite. The magnetic behavior of the PMMA/Fe-oxide nanocomposites is investigated. The transparent PMMA/Fe-oxide nanocomposite has potentially interesting magneto-optic applications without compromising the advantages of a lightweight, noncorrosive polymeric material with very high transparency even for bulk samples.

The application of the symmetry properties of optical second harmonic generation to studies of interfaces and gases

International Nuclear Information System (INIS)

Feller, M.B.

1991-11-01

Optical second harmonic generation has proven to be a powerful tool for studying interfaces. The symmetry properties of the process allow for surface sensitivity not available with other optical methods. In this thesis, we take advantage of these symmetry properties SHG to study a variety of interesting systems not previously studied with this technique. We show that optical second harmonic generation is an effective surface probe with a submonolayer sensitivity for media without inversion symmetry. We demonstrate the technique at a gallium arsenide surface, exploiting the different symmetry properties of the bulk and surface of the crystal to isolate the surface contribution. We also demonstrate that optical second harmonic generation can be used to determine the anisotropic orientational distribution of a surface monolayer of molecules. We apply the technique to study homogeneously aligned liquid crystal cells. To further explore the LC-polymer interface, we used SHG to study the surface memory effect. The surface memory effect is the rendering of an isotropic interface anisotropic by putting it in contact with an anisotropic bulk. Last, we describe some preliminary measurements of a time-resolved spectroscopic study of the phenomenon of second harmonic generation in a gas. The construction of a 500 microjoule pulsed, tunable laser source is described

The application of the symmetry properties of optical second harmonic generation to studies of interfaces and gases

Energy Technology Data Exchange (ETDEWEB)

Feller, Marla Beth [Univ. of California, Berkeley, CA (United States)

1991-11-01

Optical second harmonic generation has proven to be a powerful tool for studying interfaces. The symmetry properties of the process allow for surface sensitivity not available with other optical methods. In this thesis, we take advantage of these symmetry properties SHG to study a variety of interesting systems not previously studied with this technique. We show that optical second harmonic generation is an effective surface probe with a submonolayer sensitivity for media without inversion symmetry. We demonstrate the technique at a gallium arsenide surface, exploiting the different symmetry properties of the bulk and surface of the crystal to isolate the surface contribution. We also demonstrate that optical second harmonic generation can be used to determine the anisotropic orientational distribution of a surface monolayer of molecules. We apply the technique to study homogeneously aligned liquid crystal cells. To further explore the LC-polymer interface, we used SHG to study the surface memory effect. The surface memory effect is the rendering of an isotropic interface anisotropic by putting it in contact with an anisotropic bulk. Last, we describe some preliminary measurements of a time-resolved spectroscopic study of the phenomenon of second harmonic generation in a gas. The construction of a 500 microjoule pulsed, tunable laser source is described.

Study of optical properties of Erbium doped Tellurite glass-polymer composite

Energy Technology Data Exchange (ETDEWEB)

Sushama, D., E-mail: sushasukumar@gmail.com [Research Awardee, LAMP, Dept. of Physics, Nit, Calicut, India and Dept. of Physics, M.S.M. College, Kayamkulam, Kerala (India)

2014-10-15

Chalcogenide glasses have wide applications in optical device technology. But it has some disadvantages like thermal instability. Among them Tellurite glasses exhibits high thermal Stability. Doping of rare earth elements into the Tellurite glasses improve its optical properties. To improve its mechanical properties composites of this Tellurite glasses with polymer are prepared. Bulk samples of Er{sub 2}O{sub 3} doped TeO{sub 2}‐WO{sub 3}‐La{sub 2}O{sub 3} Tellurite glasses are prepared from high purity oxide mixtures, melting in an alumina crucible in air atmosphere. Composites of this Tellurite glasses with polymer are prepared by powder mixing method and the thin films of these composites are prepared using polymer press. Variations in band gap of these composites are studied from the UV/Vis/NIR absorption.

Study of optical properties of Erbium doped Tellurite glass-polymer composite

International Nuclear Information System (INIS)

Sushama, D.

2014-01-01

Chalcogenide glasses have wide applications in optical device technology. But it has some disadvantages like thermal instability. Among them Tellurite glasses exhibits high thermal Stability. Doping of rare earth elements into the Tellurite glasses improve its optical properties. To improve its mechanical properties composites of this Tellurite glasses with polymer are prepared. Bulk samples of Er 2 O 3 doped TeO 2 ‐WO 3 ‐La 2 O 3 Tellurite glasses are prepared from high purity oxide mixtures, melting in an alumina crucible in air atmosphere. Composites of this Tellurite glasses with polymer are prepared by powder mixing method and the thin films of these composites are prepared using polymer press. Variations in band gap of these composites are studied from the UV/Vis/NIR absorption

Structural, electronic, linear, and nonlinear optical properties of ZnCdTe{sub 2} chalcopyrite

Energy Technology Data Exchange (ETDEWEB)

Ouahrani, Tarik [Laboratoire de Physique Theorique, Universite de Tlemcen, B.P. 230, Tlemcen 13000 (Algeria); Reshak, Ali H. [Institute of Physical Biology, South Bohemia University, Nove Hrady 37333 (Czech Republic); School of Microelectronic Engineering, University of Malaysia Perlis (UniMAP), Block A, Kompleks Pusat Pengajian, 02600 Arau Jejawi, Perlis (Malaysia); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique, Universite de Mascara, Mascara 29000 (Algeria); Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Baltache, H.; Amrani, B. [Laboratoire de Physique Quantique et de Modelisation Mathematique, Universite de Mascara, Mascara 29000 (Algeria); Bouhemadou, A. [Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Faculty of Sciences, Department of Physics, University of Setif, Setif 19000 (Algeria)

2011-03-15

We report results of first-principles density functional calculations using the full-potential linearized augmented plane wave method. The generalized gradient approximation (GGA) and the Engel-Vosko-GGA (EV-GGA) formalism were used for the exchange-correlation energy to calculate the structural, electronic, linear, and nonlinear optical properties of the chalcopyrite ZnCdTe{sub 2} compound. The valence band maximum and the conduction band minimum are located at the {gamma}-point, resulting in a direct band gap of about 0.71 eV for GGA and 1.29 eV for EV-GGA. The results of bulk properties, such as lattice parameters (a, c, and u), bulk modulus B, and its pressure derivative B' are evaluated. The optical properties of this compound, namely the real and the imaginary parts of the dielectric function, reflectivity, and refractive index, show a considerable anisotropy as a consequence ZnCdTe{sub 2} posseses a strong birefringence. In addition, the extinction coefficient, the electron energy loss function, and the nonlinear susceptibility are calculated and their spectra are analyzed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Bulk Fermi surface and electronic properties of Cu0.07Bi2Se3

Science.gov (United States)

Martin, C.; Craciun, V.; Miller, K. H.; Uzakbaiuly, B.; Buvaev, S.; Berger, H.; Hebard, A. F.; Tanner, D. B.

2013-05-01

The electronic properties of Cu0.07Bi2Se3 have been investigated using Shubnikov-de Haas and optical reflectance measurements. Quantum oscillations reveal a bulk, three-dimensional Fermi surface with anisotropy kFc/kFab≈ 2 and a modest increase in free-carrier concentration and in scattering rate with respect to the undoped Bi2Se3, also confirmed by reflectivity data. The effective mass is almost identical to that of Bi2Se3. Optical conductivity reveals a strong enhancement of the bound impurity bands with Cu addition, suggesting that a significant number of Cu atoms enter the interstitial sites between Bi and Se layers or may even substitute for Bi. This conclusion is also supported by x-ray diffraction measurements, where a significant increase of microstrain was found in Cu0.07Bi2Se3, compared to Bi2Se3.

First-Principles Investigation of Phase Stability, Electronic Structure and Optical Properties of MgZnO Monolayer

Directory of Open Access Journals (Sweden)

Changlong Tan

2016-10-01

Full Text Available MgZnO bulk has attracted much attention as candidates for application in optoelectronic devices in the blue and ultraviolet region. However, there has been no reported study regarding two-dimensional MgZnO monolayer in spite of its unique properties due to quantum confinement effect. Here, using density functional theory calculations, we investigated the phase stability, electronic structure and optical properties of MgxZn1−xO monolayer with Mg concentration x range from 0 to 1. Our calculations show that MgZnO monolayer remains the graphene-like structure with various Mg concentrations. The phase segregation occurring in bulk systems has not been observed in the monolayer due to size effect, which is advantageous for application. Moreover, MgZnO monolayer exhibits interesting tuning of electronic structure and optical properties with Mg concentration. The band gap increases with increasing Mg concentration. More interestingly, a direct to indirect band gap transition is observed for MgZnO monolayer when Mg concentration is higher than 75 at %. We also predict that Mg doping leads to a blue shift of the optical absorption peaks. Our results may provide guidance for designing the growth process and potential application of MgZnO monolayer.

Mass production of bulk artificial nacre with excellent mechanical properties.

Science.gov (United States)

Gao, Huai-Ling; Chen, Si-Ming; Mao, Li-Bo; Song, Zhao-Qiang; Yao, Hong-Bin; Cölfen, Helmut; Luo, Xi-Sheng; Zhang, Fu; Pan, Zhao; Meng, Yu-Feng; Ni, Yong; Yu, Shu-Hong

2017-08-18

Various methods have been exploited to replicate nacre features into artificial structural materials with impressive structural and mechanical similarity. However, it is still very challenging to produce nacre-mimetics in three-dimensional bulk form, especially for further scale-up. Herein, we demonstrate that large-sized, three-dimensional bulk artificial nacre with comprehensive mimicry of the hierarchical structures and the toughening mechanisms of natural nacre can be facilely fabricated via a bottom-up assembly process based on laminating pre-fabricated two-dimensional nacre-mimetic films. By optimizing the hierarchical architecture from molecular level to macroscopic level, the mechanical performance of the artificial nacre is superior to that of natural nacre and many engineering materials. This bottom-up strategy has no size restriction or fundamental barrier for further scale-up, and can be easily extended to other material systems, opening an avenue for mass production of high-performance bulk nacre-mimetic structural materials in an efficient and cost-effective way for practical applications.Artificial materials that replicate the mechanical properties of nacre represent important structural materials, but are difficult to produce in bulk. Here, the authors exploit the bottom-up assembly of 2D nacre-mimetic films to fabricate 3D bulk artificial nacre with an optimized architecture and excellent mechanical properties.

129Xe NMR spectroscopy in microporous solids: The effect of bulk properties

International Nuclear Information System (INIS)

Ripmeester, John A.; Ratcliffe, Christopher I.

1993-01-01

In this contribution we point out a number of factors related to the bulk properties of microporous solids which must be taken into account in order first of all to obtain meaningful 129 Xe NMR spectral data, and secondly to interpret the data properly. This sensitivity to bulk properties is especially important for microporous solids where there is little or no barrier to xenon passage from inside the particle to the interparticle space. We examine the effect of particle size, powder bulk density and particle anisotropy, and also the effect of low thermal conductivity of low density powders

Thermal treatment induced modification of structural, surface and bulk magnetic properties of Fe61.5Co5Ni8Si13.5B9Nb3 metallic glass

Science.gov (United States)

Shah, M.; Satalkar, M.; Kane, S. N.; Ghodke, N. L.; Sinha, A. K.; Varga, L. K.; Teixeira, J. M.; Araujo, J. P.

2018-05-01

Effect of thermal annealing induced modification of structural, surface and bulk magnetic properties of Fe61.5Co5Ni8Si13.5B9Nb3 alloy is presented. The changes in properties were observed using synchrotron x-ray diffraction technique (SXRD), atomic force microscopy (AFM), magneto-optical kerr effect (MOKE) and bulk magnetic measurements. Significant variations on the both side of surface occur for the annealing temperature upto 500 °C promotes the surface crystallization. Surface roughness appears due to presence of nanocrystallization plays an important role in determining magnetic properties. Observed lower value of bulk coercivity Hc of 6.2 A/m annealed temperature at 450 °C/1 h ascribed to reduction of disorder as compared to the surface (both shiny and wheel side observed by MOKE measurement) whereas improvement of bulk saturation magnetization with annealing temperature indicates first near neighbor shell of Fe atoms are surrounded by Fe atoms. Evolution of coercivity of surface and bulk with annealing temperature has been presented in conjunction with the structural observations.

Relationships among surface processing at the nanometer scale, nanostructure and optical properties of thin oxide films

Energy Technology Data Exchange (ETDEWEB)

Losurdo, Maria

2004-05-01

Spectroscopic ellipsometry is used to study the optical properties of nanostructured semiconductor oxide thin films. Various examples of models for the dielectric function, based on Lorentzian oscillators combined with the Drude model, are given based on the band structure of the analyzed oxide. With this approach, the optical properties of thin films are determined independent of the dielectric functions of the corresponding bulk materials, and correlation between the optical properties and nanostructure of thin films is investigated. In particular, in order to discuss the dependence of optical constants on grain size, CeO{sub 2} nanostructured films are considered and parameterized by two-Lorentzian oscillators or two-Tauc-Lorentz model depending on the nanostructure and oxygen deficiency. The correlation among anisotropy, crystalline fraction and optical properties parameterized by a four-Lorentz oscillator model is discussed for nanocrystalline V{sub 2}O{sub 5} thin films. Indium tin oxide thin films are discussed as an example of the presence of graded optical properties related to interfacial reactivity activated by processing conditions. Finally, the example of ZnO shows the potential of ellipsometry in discerning crystal and epitaxial film polarity through the analysis of spectra and the detection of surface reactivity of the two polar faces, i.e. Zn-polarity and O-polarity.

Electronic and Optical Properties of Two-Dimensional GaN from First-Principles.

Science.gov (United States)

Sanders, Nocona; Bayerl, Dylan; Shi, Guangsha; Mengle, Kelsey A; Kioupakis, Emmanouil

2017-12-13

Gallium nitride (GaN) is an important commercial semiconductor for solid-state lighting applications. Atomically thin GaN, a recently synthesized two-dimensional material, is of particular interest because the extreme quantum confinement enables additional control of its light-emitting properties. We performed first-principles calculations based on density functional and many-body perturbation theory to investigate the electronic, optical, and excitonic properties of monolayer and bilayer two-dimensional (2D) GaN as a function of strain. Our results demonstrate that light emission from monolayer 2D GaN is blueshifted into the deep ultraviolet range, which is promising for sterilization and water-purification applications. Light emission from bilayer 2D GaN occurs at a similar wavelength to its bulk counterpart due to the cancellation of the effect of quantum confinement on the optical gap by the quantum-confined Stark shift. Polarized light emission at room temperature is possible via uniaxial in-plane strain, which is desirable for energy-efficient display applications. We compare the electronic and optical properties of freestanding two-dimensional GaN to atomically thin GaN wells embedded within AlN barriers in order to understand how the functional properties are influenced by the presence of barriers. Our results provide microscopic understanding of the electronic and optical characteristics of GaN at the few-layer regime.

First-principle calculations of the electronic, optical and elastic properties of ZnSiP2 semiconductor

International Nuclear Information System (INIS)

Kumar, V.; Tripathy, S.K.

2014-01-01

Highlights: • Optical properties of ZnSiP 2 studied under different pressure for stable structure. • Birefringence has been calculated at different wavelengths. • Lattice constants, ħω p , bulk modulus and its derivative have been calculated. • C ij , Y, υ and Zener anisotropic factor have also been estimated. • Our calculated values are relative more close to the experimental values. -- Abstract: The plane wave pseudo-potential method within density functional theory (DFT) has been used to investigate the structural, electronic, optical and elastic properties of ZnSiP 2 chalcopyrite semiconductor. The lattice constants are calculated from the optimized unit cells and compare with the experimental value. The band structure, total density of states (TDOS) and partial density of states (PDOS) have been discussed. The energy gap has been calculated along the Γ direction found to be 1.383 eV, which shows that ZnSiP 2 is pseudo-direct in nature. We have also analyzed the frequency dependent dielectric constant ε(ω) and calculated the birefringence (Δn). The optical properties under three different hydrostatic pressures of 0 GPa, 10 GPa and 20 GPa have been described for the first time in the energy range 0–20 eV. The values of bulk modulus (B), pressure derivative of bulk modulus (B ∗ ), elastic constants (C ij ), Young’s modulus (Y), anisotropic factor (A) and Poisson’s ratio (ν) have been calculated. The calculated values of all above parameters are compared with the available experimental values and the values reported by different workers. A fairly good agreement has been found between them

Electronic, elastic and optical properties of ZnGeP{sub 2} semiconductor under hydrostatic pressures

Energy Technology Data Exchange (ETDEWEB)

Tripathy, S.K.; Kumar, V., E-mail: vkumar52@hotmail.com

2014-03-15

The electronic, elastic and optical properties of zinc germanium phosphide, ZnGeP{sub 2}, semiconductor have been studied using local density approximation (LDA) method within the density functional theory (DFT). The lattice constants (a and c), band structure, density of states (DOS), bulk modulus (B) and pressure derivative of bulk modulus (B′) have been discussed. The value of pseudo-direct band gap (E{sub g}) at Γ point has been calculated. The pressure dependences of elastic stiffness coefficients (C{sub ij}), Zener anisotropy factor (A), Poisson's ratio (ν), Young modulus (Y) and shear modulus (G) have also been calculated. The ratio of B/G shows that that ZnGeP{sub 2} is ductile in nature. The optical properties have been discussed in detail under three different pressures in the energy range 0–22 eV. The calculated values of all parameters are compared with the available experimental values and the values reported by different workers. Reasonably good agreement has been obtained between them.

Elastic properties of superconducting bulk metallic glasses

International Nuclear Information System (INIS)

Hempel, Marius

2015-01-01

Within the framework of this thesis the elastic properties of a superconducting bulk metallic glass between 10 mK and 300 K were first investigated. In order to measure the entire temperature range, in particular the low temperature part, new experimental techniques were developed. Using an inductive readout scheme for a double paddle oscillator it was possible to determine the internal friction and the relative change of sound velocity of bulk metallic glasses with high precision. This allowed for a detailed comparison of the data with different models. The analysis focuses on the low temperature regime where the properties of glassy materials are governed by atomic tunneling systems as described by the tunneling model. The influence of conduction electrons in the normal conducting state and quasiparticles in the superconducting state of the glass were accounted for in the theoretical description, resulting in a good agreement over a large temperature range between measured data and prediction of the tunneling model. This allowed for a direct determination of the coupling constant between electrons and tunneling systems. In the vicinity of the transition temperature Tc the data can only be described if a modified distribution function of the tunneling parameters is applied.

Optical and scintillation properties of bulk ZnO crystal

Energy Technology Data Exchange (ETDEWEB)

Yanagida, Takayuki [Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu, Kitakyushu 808-0196 (Japan); Fujimoto, Yutaka; Kurosawa, Shunsuke [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Yamanoi, Kohei; Sarukura, Nobuhiko [Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Kano, Masataka; Wakamiya, Akira [Daishinku Corporation, 1389 Shinzaike, Hiraoka-cho, Kakogawa, Hyogo 675-0194 (Japan)

2012-12-15

Single crystal bulk ZnO scintillator grown by the hydrothermal method was tested on its scintillation performances. In X-ray induced radio luminescence spectrum, it exhibited two intense emission peaks at 400 and 550 nm. The former was ascribed to the free and bound exciton related luminescence and the latter to oxygen vacancy related one, respectively. X-ray induced scintillation decay time of the exciton related emission measured by the pulse X-ray streak camera system resulted {proportional_to} 4 ns. Finally, the light yield under {sup 241}Am 5.5 MeV {alpha}-ray was examined and it resulted {proportional_to} 500 ph/5.5 MeV-{alpha}.(copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Controlling the scattering properties of thin, particle-doped coatings

Science.gov (United States)

Rogers, William; Corbett, Madeleine; Manoharan, Vinothan

2013-03-01

Coatings and thin films of small particles suspended in a matrix possess optical properties that are important in several industries from cosmetics and paints to polymer composites. Many of the most interesting applications require coatings that produce several bulk effects simultaneously, but it is often difficult to rationally formulate materials with these desired optical properties. Here, we focus on the specific challenge of designing a thin colloidal film that maximizes both diffuse and total hemispherical transmission. We demonstrate that these bulk optical properties follow a simple scaling with two microscopic length scales: the scattering and transport mean free paths. Using these length scales and Mie scattering calculations, we generate basic design rules that relate scattering at the single particle level to the film's bulk optical properties. These ideas will be useful in the rational design of future optically active coatings.

Organic bulk heterojunction photovoltaic structures: design, morphology and properties

International Nuclear Information System (INIS)

Bulavko, G V; Ishchenko, A A

2014-01-01

Main approaches to the design of organic bulk heterojunction photovoltaic structures are generalized and systematized. Novel photovoltaic materials based on fullerenes, organic dyes and related compounds, graphene, conjugated polymers and dendrimers are considered. The emphasis is placed on correlations between the chemical structure and properties of materials. The effect of morphology of the photoactive layer on the photovoltaic properties of devices is analyzed. Main methods of optimization of the photovoltaic properties are outlined. The bibliography includes 338 references

Ab-initio investigations of the electronic properties of bulk wurtzite Beryllia and its derived nanofilms

International Nuclear Information System (INIS)

Goumri-Said, Souraya; Kanoun, Mohammed Benali

2010-01-01

In this Letter we investigate the electronic properties of the bulk and the nanofilm BeO in wurtzite structure. We performed a first-principles pseudo-potential method within the generalized gradient approximation. We will give more importance to the changes in band structure and density of states between the bulk structure and its derived nanofilms. The bonding characterization will be investigated via the analysis Mulliken population and charge density contours. It is found that the nanofilm retains the same properties as its bulk structure with slight changes in electronic properties and band structure which may offer some unusual transport properties.

Optical properties of C-doped bulk GaN wafers grown by halide vapor phase epitaxy

International Nuclear Information System (INIS)

Khromov, S.; Hemmingsson, C.; Monemar, B.; Hultman, L.; Pozina, G.

2014-01-01

Freestanding bulk C-doped GaN wafers grown by halide vapor phase epitaxy are studied by optical spectroscopy and electron microscopy. Significant changes of the near band gap (NBG) emission as well as an enhancement of yellow luminescence have been found with increasing C doping from 5 × 10 16 cm −3 to 6 × 10 17 cm −3 . Cathodoluminescence mapping reveals hexagonal domain structures (pits) with high oxygen concentrations formed during the growth. NBG emission within the pits even at high C concentration is dominated by a rather broad line at ∼3.47 eV typical for n-type GaN. In the area without pits, quenching of the donor bound exciton (DBE) spectrum at moderate C doping levels of 1–2 × 10 17 cm −3 is observed along with the appearance of two acceptor bound exciton lines typical for Mg-doped GaN. The DBE ionization due to local electric fields in compensated GaN may explain the transformation of the NBG emission

Optical and Electrical Characterization of Melt-Grown Bulk Indium Gallium Arsenide and Indium Arsenic Phosphide Alloys

Science.gov (United States)

2011-03-01

spectrum, photoluminescence (PL), and refractive index measurements. Other methods such as infrared imagery and micro probe wavelength dispersing ...States. AFIT/DS/ENP/11-M02 OPTICAL AND ELECTRICAL CHARACTERIZATION OF MELT- GROWN BULK INDIUM GALLIUM ARSENIDE AND INDIUM ARSENIC PHOSPHIDE ...CHARACTERIZATION OF MELT-GROWN BULK INDIUM GALLIUM ARSENIDE AND INDIUM ARSENIC PHOSPHIDE ALLOYS Jean Wei, BS, MS Approved

Optical adhesive property study

Energy Technology Data Exchange (ETDEWEB)

Sundvold, P.D.

1996-01-01

Tests were performed to characterize the mechanical and thermal properties of selected optical adhesives to identify the most likely candidate which could survive the operating environment of the Direct Optical Initiation (DOI) program. The DOI system consists of a high power laser and an optical module used to split the beam into a number of channels to initiate the system. The DOI requirements are for a high shock environment which current military optical systems do not operate. Five candidate adhesives were selected and evaluated using standardized test methods to determine the adhesives` physical properties. EC2216, manufactured by 3M, was selected as the baseline candidate adhesive based on the test results of the physical properties.

Optical properties and electronic structure of the Cu–Zn brasses

International Nuclear Information System (INIS)

Keast, V.J.; Ewald, J.; De Silva, K.S.B.; Cortie, M.B.; Monnier, B.; Cuskelly, D.; Kisi, E.H.

2015-01-01

The color of Cu–Zn brasses range from the red of copper through bright yellow to grey-silver as the Zn content increases. Here we examine the mechanism by which these color changes occur. The optical properties of this set of alloys has been calculated using density functional theory (DFT) and compared to experimental spectroscopy measurements. The optical response of the low Zn content α-brasses is shown to have a distinctly different origin to that in the higher content β′, γ and ε-brasses. The response of β′-brass is unique in that it is strongly influenced by an overdamped plasmon excitation and this alloy will also have a strong surface plasmon response. - Highlights: • Study of the electronic structure and optical response of the Cu–Zn brasses. • Agreement between experiment and calculation of the dielectric functions. • α-brasses optical response is dominated by transitions from the top of the d-band. • In the other brasses it is transitions around the Fermi level. • β′-brass response is dominateed by an overdamped bulk plasmonic response

Optical properties and electronic structure of the Cu–Zn brasses

Energy Technology Data Exchange (ETDEWEB)

Keast, V.J., E-mail: vicki.keast@newcastle.edu.au [School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW 2308 (Australia); Ewald, J. [School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW 2308 (Australia); De Silva, K.S.B.; Cortie, M.B. [Institute for Nanoscale Technology, University of Technology Sydney, PO Box 123, Broadway, NSW 2007 (Australia); Monnier, B. [School of Engineering, The University of Newcastle, Callaghan, NSW 2308 (Australia); Universite de Technologie de Troyes, 12 Rue Marie Curie, BP 2060, 10010 Troyes Cedex (France); Cuskelly, D.; Kisi, E.H. [School of Engineering, The University of Newcastle, Callaghan, NSW 2308 (Australia)

2015-10-25

The color of Cu–Zn brasses range from the red of copper through bright yellow to grey-silver as the Zn content increases. Here we examine the mechanism by which these color changes occur. The optical properties of this set of alloys has been calculated using density functional theory (DFT) and compared to experimental spectroscopy measurements. The optical response of the low Zn content α-brasses is shown to have a distinctly different origin to that in the higher content β′, γ and ε-brasses. The response of β′-brass is unique in that it is strongly influenced by an overdamped plasmon excitation and this alloy will also have a strong surface plasmon response. - Highlights: • Study of the electronic structure and optical response of the Cu–Zn brasses. • Agreement between experiment and calculation of the dielectric functions. • α-brasses optical response is dominated by transitions from the top of the d-band. • In the other brasses it is transitions around the Fermi level. • β′-brass response is dominateed by an overdamped bulk plasmonic response.

Analysis of optical and electronic properties of MoS2 for optoelectronics and FET applications

Science.gov (United States)

Ullah, Muhammad S.; Yousuf, Abdul Hamid Bin; Es-Sakhi, Azzedin D.; Chowdhury, Masud H.

2018-04-01

Molybdenum disulfide (MoS2) is considered as a promising alternative to conventional semiconductor materials that used in the IC industry because of its novel properties. In this paper, we explore the optical and electronic properties of MoS2 for photodetector and transistors applications. This simulation is done using `DFT materials properties simulator'. Our findings show that mono- and multi-layer MoS2 is suitable for conventional and tunnel FET applications due to direct and indirect band-gap respectively. The bulk MoS2 crystal, which are composed of stacked layers have indirect bandgap and mono-layer MoS2 crystal form direct bandgap at the K-point of Brillouin zone. Indirect bandgap of bulk MoS2 crystal implies that phonons need to be involved in band-to-band tunneling (BTBT) process. Degenerately doped semiconductor, which is basically spinning the Fermi level, changing the DOS profile, and thinning the indirect bandgap that allow tunneling from valence band to conduction band. The optical properties of MoS2 is explored in terms of Absorption coefficient, extinction coefficient and refractive index. Our results shows that a MoS2 based photodetector can be fabricate to detect light in the visible range (below 500nm). It is also observed that the MoS2 is most sensitive for the light of wavelength 450nm.

Unexpected optical limiting properties from MoS2 nanosheets modified by a semiconductive polymer.

Science.gov (United States)

Zhao, Min; Chang, Meng-Jie; Wang, Qiang; Zhu, Zhen-Tong; Zhai, Xin-Ping; Zirak, Mohammad; Moshfegh, Alireza Z; Song, Ying-Lin; Zhang, Hao-Li

2015-08-07

Direct solvent exfoliation of bulk MoS2 with the assistance of poly(3-hexylthiophene) (P3HT) produces a novel two-dimensional organic/inorganic semiconductor hetero-junction. The obtained P3HT-MoS2 nanohybrid exhibits unexpected optical limiting properties in contrast to the saturated absorption behavior of both P3HT and MoS2, showing potential in future photoelectric applications.

Doping of wide-bandgap titanium-dioxide nanotubes: optical, electronic and magnetic properties

Science.gov (United States)

Alivov, Yahya; Singh, Vivek; Ding, Yuchen; Cerkovnik, Logan Jerome; Nagpal, Prashant

2014-08-01

Doping semiconductors is an important step for their technological application. While doping bulk semiconductors can be easily achieved, incorporating dopants in semiconductor nanostructures has proven difficult. Here, we report a facile synthesis method for doping titanium-dioxide (TiO2) nanotubes that was enabled by a new electrochemical cell design. A variety of optical, electronic and magnetic dopants were incorporated into the hollow nanotubes, and from detailed studies it is shown that the doping level can be easily tuned from low to heavily-doped semiconductors. Using desired dopants - electronic (p- or n-doped), optical (ultraviolet bandgap to infrared absorption in co-doped nanotubes), and magnetic (from paramagnetic to ferromagnetic) properties can be tailored, and these technologically important nanotubes can be useful for a variety of applications in photovoltaics, display technologies, photocatalysis, and spintronic applications.Doping semiconductors is an important step for their technological application. While doping bulk semiconductors can be easily achieved, incorporating dopants in semiconductor nanostructures has proven difficult. Here, we report a facile synthesis method for doping titanium-dioxide (TiO2) nanotubes that was enabled by a new electrochemical cell design. A variety of optical, electronic and magnetic dopants were incorporated into the hollow nanotubes, and from detailed studies it is shown that the doping level can be easily tuned from low to heavily-doped semiconductors. Using desired dopants - electronic (p- or n-doped), optical (ultraviolet bandgap to infrared absorption in co-doped nanotubes), and magnetic (from paramagnetic to ferromagnetic) properties can be tailored, and these technologically important nanotubes can be useful for a variety of applications in photovoltaics, display technologies, photocatalysis, and spintronic applications. Electronic supplementary information (ESI) available: See DOI: 10.1039/c4nr02417f

Quantum theory of the optical and electronic properties of semiconductors

CERN Document Server

Haug, Hartmut

2009-01-01

This invaluable textbook presents the basic elements needed to understand and research into semiconductor physics. It deals with elementary excitations in bulk and low-dimensional semiconductors, including quantum wells, quantum wires and quantum dots. The basic principles underlying optical nonlinearities are developed, including excitonic and many-body plasma effects. Fundamentals of optical bistability, semiconductor lasers, femtosecond excitation, the optical Stark effect, the semiconductor photon echo, magneto-optic effects, as well as bulk and quantum-confined Franz-Keldysh effects, are covered. The material is presented in sufficient detail for graduate students and researchers with a general background in quantum mechanics.This fifth edition includes an additional chapter on 'Quantum Optical Effects' where the theory of quantum optical effects in semiconductors is detailed. Besides deriving the 'semiconductor luminescence equations' and the expression for the stationary luminescence spectrum, the resu...

Ab-initio investigations of the electronic properties of bulk wurtzite Beryllia and its derived nanofilms

KAUST Repository

Goumri-Said, Souraya

2010-08-01

In this Letter we investigate the electronic properties of the bulk and the nanofilm BeO in wurtzite structure. We performed a first-principles pseudo-potential method within the generalized gradient approximation. We will give more importance to the changes in band structure and density of states between the bulk structure and its derived nanofilms. The bonding characterization will be investigated via the analysis Mulliken population and charge density contours. It is found that the nanofilm retains the same properties as its bulk structure with slight changes in electronic properties and band structure which may offer some unusual transport properties. © 2010 Elsevier B.V. All rights reserved.

Probing the micro-rheological properties of aerosol particles using optical tweezers

International Nuclear Information System (INIS)

Power, Rory M; Reid, Jonathan P

2014-01-01

The use of optical trapping techniques to manipulate probe particles for performing micro-rheological measurements on a surrounding fluid is well-established. Here, we review recent advances made in the use of optical trapping to probe the rheological properties of trapped particles themselves. In particular, we review observations of the continuous transition from liquid to solid-like viscosity of sub-picolitre supersaturated solution aerosol droplets using optical trapping techniques. Direct measurements of the viscosity of the particle bulk are derived from the damped oscillations in shape following coalescence of two particles, a consequence of the interplay between viscous and surface forces and the capillary driven relaxation of the approximately spheroidal composite particle. Holographic optical tweezers provide a facile method for the manipulation of arrays of particles allowing coalescence to be controllably induced between two micron-sized aerosol particles. The optical forces, while sufficiently strong to confine the composite particle, are several orders of magnitude weaker than the capillary forces driving relaxation. Light, elastically back-scattered by the particle, is recorded with sub-100 ns resolution allowing measurements of fast relaxation (low viscosity) dynamics, while the brightfield image can be used to monitor the shape relaxation extending to times in excess of 1000 s. For the slowest relaxation dynamics studied (particles with the highest viscosity) the presence and line shape of whispering gallery modes in the cavity enhanced Raman spectrum can be used to infer the relaxation time while serving the dual purpose of allowing the droplet size and refractive index to be measured with accuracies of ±0.025% and ±0.1%, respectively. The time constant for the damped relaxation can be used to infer the bulk viscosity, spanning from the dilute solution limit to a value approaching that of a glass, typically considered to be >10 12 �

Probing the micro-rheological properties of aerosol particles using optical tweezers

Science.gov (United States)

Power, Rory M.; Reid, Jonathan P.

2014-07-01

The use of optical trapping techniques to manipulate probe particles for performing micro-rheological measurements on a surrounding fluid is well-established. Here, we review recent advances made in the use of optical trapping to probe the rheological properties of trapped particles themselves. In particular, we review observations of the continuous transition from liquid to solid-like viscosity of sub-picolitre supersaturated solution aerosol droplets using optical trapping techniques. Direct measurements of the viscosity of the particle bulk are derived from the damped oscillations in shape following coalescence of two particles, a consequence of the interplay between viscous and surface forces and the capillary driven relaxation of the approximately spheroidal composite particle. Holographic optical tweezers provide a facile method for the manipulation of arrays of particles allowing coalescence to be controllably induced between two micron-sized aerosol particles. The optical forces, while sufficiently strong to confine the composite particle, are several orders of magnitude weaker than the capillary forces driving relaxation. Light, elastically back-scattered by the particle, is recorded with sub-100 ns resolution allowing measurements of fast relaxation (low viscosity) dynamics, while the brightfield image can be used to monitor the shape relaxation extending to times in excess of 1000 s. For the slowest relaxation dynamics studied (particles with the highest viscosity) the presence and line shape of whispering gallery modes in the cavity enhanced Raman spectrum can be used to infer the relaxation time while serving the dual purpose of allowing the droplet size and refractive index to be measured with accuracies of ±0.025% and ±0.1%, respectively. The time constant for the damped relaxation can be used to infer the bulk viscosity, spanning from the dilute solution limit to a value approaching that of a glass, typically considered to be >1012 Pa s, whilst

Electronic, elastic, acoustic and optical properties of cubic TiO2: A DFT approach

International Nuclear Information System (INIS)

Mahmood, Tariq; Cao, Chuanbao; Tahir, Muhammad; Idrees, Faryal; Ahmed, Maqsood; Tanveer, M.; Aslam, Imran; Usman, Zahid; Ali, Zulfiqar; Hussain, Sajad

2013-01-01

The electronic, elastic, acoustic and optical properties of cubic phases TiO 2 fluorite and pyrite are investigated using the first principles calculations. We have employed five different exchange–correlation functions within the local density and generalized gradient approximations using the ultrasoft plane wave pseudopotential method. The calculated band structures of cubic-TiO 2 elucidate that the TiO 2 fluorite and pyrite are direct and indirect semiconductors in contrast to the previous findings. From our studied properties such as bulk and shear moduli, elastic constants C 44 and Debye temperature for TiO 2 fluorite and pyrite, we infer that both the cubic phases are not superhard materials and the pyrite phase is harder than fluorite. The longitudinal and transversal acoustic wave speeds for both phases in the directions [100], [110] and [111] are determined using the pre-calculated elastic constants. In addition, we also calculate the optical properties such as dielectric function, absorption spectrum, refractive index and energy loss function using the pre-optimized structure. On the observation of optical properties TiO 2 fluorite phase turn out to be more photocatalytic than pyrite

The optical, vibrational, structural and elasto-optic properties of Zn_0_._2_5Cd_0_._7_5S_ySe_1_-_y quaternary alloys

International Nuclear Information System (INIS)

Paliwal, U.; Swarkar, C. B.; Sharma, M. D.; Joshi, K. B.

2016-01-01

The optical, vibrational, structural and elasto-optic properties of quaternary II-VI alloys Zn_0_._2_5Cd_0_._7_5S_0_._2_5Se_0_._7_5, Zn_0_._2_5Cd_0_._7_5S_0_._5_0Se_0_._5_0 and Zn_0_._2_5Cd_0_._7_5S_0_._7_5Se_0_._2_5 are presented. Within the empirical pseudopotential method (EPM) the disorder effects are modeled via modified virtual crystal approximation (MVCA). The computed bandgaps and the refined form factors are utilized to evaluate optical, vibrational, structural and elasto-optic properties. The refractive index (n), static (ε_0) and high frequency dielectric (ε_∞) constants are calculated to reveal optical behavior of alloys. The longitudinal ω_L_O(0) and transverse ω_T_O(0) optical frequencies are obtained to see vibrational characteristics. Moreover, the elastic constants (c_i_j) and bulk moduli (B) are computed by combining the EPM with Harrison bond orbital model. The elasto-optic nature of alloys is examined by computing the photo-elastic constants. These values are significant with regard to the opto-electronic applications especially when no experimental data are available on this system.

Growth and optical properties of CMOS-compatible silicon nanowires for photonic devices

Science.gov (United States)

Guichard, Alex Richard

Silicon (Si) is the dominant semiconductor material in both the microelectronic and photovoltaic industries. Despite its poor optical properties, Si is simply too abundant and useful to be completely abandoned in either industry. Since the initial discovery of efficient room temperature photoluminescence (PL) from porous Si and the following discoveries of PL and time-resolved optical gain from Si nanocrystals (Si-nc) in SiO2, many groups have studied the feasibility of making Si-based, CMOS-compatible electroluminescent devices and electrically pumped lasers. These studies have shown that for Si-ne sizes below about 10 nm, PL can be attributed to radiative recombination of confined excitons and quantum efficiencies can reach 90%. PL peak energies are blue-shifted from the bulk Si band edge of 1.1 eV due to the quantum confinement effect and PL decay lifetimes are on mus timescales. However, many unanswered questions still exist about both the ease of carrier injection and various non-radiative and loss mechanisms that are present. A potential alternative material system to porous Si and Si-nc is Si nanowires (SiNWs). In this thesis, I examine the optical properties of SiNWs with diameters in the range of 3-30 nm fabricated by a number of compound metal oxide semiconductor (CMOS) compatible fabrication techniques including Chemical Vapor Deposition on metal nanoparticle coated substrates, catalytic wet etching of bulk Si and top-down electron-beam lithographic patterning. Using thermal oxidation and etching, we can increase the degree of confinement in the SiNWs. I demonstrate PL peaked in the visible and near-infrared (NIR) wavelength ranges that is tunable by controlling the crystalline SiNW core diameter, which is measured with dark field and high-resolution transmission electron microscopy. PL decay lifetimes of the SiNWs are on the order of 50 mus after proper surface passivation, which suggest that the PL is indeed from confined carriers in the SiNW cores

Bulk viscous matter-dominated Universes: asymptotic properties

Energy Technology Data Exchange (ETDEWEB)

Avelino, Arturo [Departamento de Física, Campus León, Universidad de Guanajuato, León, Guanajuato (Mexico); García-Salcedo, Ricardo [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada - Legaria del IPN, México D.F. (Mexico); Gonzalez, Tame [Departamento de Ingeniería Civil, División de Ingeniería, Universidad de Guanajuato, Guanajuato (Mexico); Nucamendi, Ulises [Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C-3, Ciudad Universitaria, CP. 58040 Morelia, Michoacán (Mexico); Quiros, Israel, E-mail: avelino@fisica.ugto.mx, E-mail: rigarcias@ipn.mx, E-mail: tamegc72@gmail.com, E-mail: ulises@ifm.umich.mx, E-mail: iquiros6403@gmail.com [Departamento de Matemáticas, Centro Universitario de Ciencias Exactas e Ingenierías (CUCEI), Corregidora 500 S.R., Universidad de Guadalajara, 44420 Guadalajara, Jalisco (Mexico)

2013-08-01

By means of a combined use of the type Ia supernovae and H(z) data tests, together with the study of the asymptotic properties in the equivalent phase space — through the use of the dynamical systems tools — we demonstrate that the bulk viscous matter-dominated scenario is not a good model to explain the accepted cosmological paradigm, at least, under the parametrization of bulk viscosity considered in this paper. The main objection against such scenarios is the absence of conventional radiation and matter-dominated critical points in the phase space of the model. This entails that radiation and matter dominance are not generic solutions of the cosmological equations, so that these stages can be implemented only by means of unique and very specific initial conditions, i. e., of very unstable particular solutions. Such a behavior is in marked contradiction with the accepted cosmological paradigm which requires of an earlier stage dominated by relativistic species, followed by a period of conventional non-relativistic matter domination, during which the cosmic structure we see was formed. Also, we found that the bulk viscosity is positive just until very late times in the cosmic evolution, around z < 1. For earlier epochs it is negative, been in tension with the local second law of thermodynamics.

Pseudopotentials for calculating the bulk and surface properties of solids

International Nuclear Information System (INIS)

Cohen, M.L.

1983-01-01

A survey is presented describing research in condensed matter physics using pseudopotentials to calculate electronic, structural, and vibrational properties of solids. Semiconductors are emphasized, and both bulk and surface calculations are discussed. (author) [pt

Calculated Bulk Properties of the Actinide Metals

DEFF Research Database (Denmark)

Skriver, Hans Lomholt; Andersen, O. K.; Johansson, B.

1978-01-01

Self-consistent relativistic calculations of the electronic properties for seven actinides (Ac-Am) have been performed using the linear muffin-tin orbitals method within the atomic-sphere approximation. Exchange and correlation were included in the local spin-density scheme. The theory explains...... the variation of the atomic volume and the bulk modulus through the 5f series in terms of an increasing 5f binding up to plutonium followed by a sudden localisation (through complete spin polarisation) in americium...

Bulk microstructure and local elastic properties of carbon nanocomposites studied by impulse acoustic microscopy technique

Science.gov (United States)

Levin, V.; Petronyuk, Yu.; Morokov, E.; Chernozatonskii, L.; Kuzhir, P.; Fierro, V.; Celzard, A.; Bellucci, S.; Bistarelli, S.; Mastrucci, M.; Tabacchioni, I.

2016-05-01

Bulk microstructure and elastic properties of epoxy-nanocarbon nanocomposites for diverse types and different content of carbon nanofiller has been studied by using impulse acoustic microscopy technique. It has been shown occurrence of various types of mesoscopic structure formed by nanoparticles inside the bulk of nanocomposite materials, including nanoparticle conglomerates and nanoparticle aerogel systems. In spite of the bulk microstructure, nanocarbon composites demonstrate elastic uniformity and negligible influence of nanofiller on elastic properties of carbon nanocomposite materials.

Finite element analysis and simulation of rheological properties of bulk molding compound (BMC)

Science.gov (United States)

Ergin, M. Fatih; Aydin, Ismail

2013-12-01

Bulk molding compound (BMC) is one of the important composite materials with various engineering applications. BMC is a thermoset plastic resin blend of various inert fillers, fiber reinforcements, catalysts, stabilizers and pigments that form a viscous, molding compound. Depending on the end-use application, bulk molding compounds are formulated to achieve close dimensional control, flame and scratch resistance, electrical insulation, corrosion and stain resistance, superior mechanical properties, low shrink and color stability. Its excellent flow characteristics, dielectric properties, and flame resistance make this thermoset material well-suited to a wide variety of applications requiring precision in detail and dimensions as well as high performance. When a BMC is used for these purposes, the rheological behavior and properties of the BMC is the main concern. In this paper, finite element analysis of rheological properties of bulk molding composite material was studied. For this purpose, standard samples of composite material were obtained by means of uniaxial hot pressing. 3 point flexural tests were then carried out by using a universal testing machine. Finite element analyses were then performed with defined material properties within a specific constitutive material behavior. Experimental and numerical results were then compared. Good correlation between the numerical simulation and the experimental results was obtained. It was expected with this study that effects of various process parameters and boundary conditions on the rheological behavior of bulk molding compounds could be determined by means of numerical analysis without detailed experimental work.

Optical properties of the c-axis oriented LiNbO3 thin film

International Nuclear Information System (INIS)

Shandilya, Swati; Sharma, Anjali; Tomar, Monika; Gupta, Vinay

2012-01-01

C-axis oriented Lithium Niobate (LiNbO 3 ) thin films have been deposited onto epitaxially matched (001) sapphire substrate using pulsed laser deposition technique. Structural and optical properties of the thin films have been studied using the X-ray diffraction (XRD) and UV–Visible spectroscopy respectively. Raman spectroscopy has been used to study the optical phonon modes and defects in the c-axis oriented LiNbO 3 thin films. XRD analysis indicates the presence of stress in the as-grown LiNbO 3 thin films and is attributed to the small lattice mismatch between LiNbO 3 and sapphire. Refractive index (n = 2.13 at 640 nm) of the (006) LiNbO 3 thin films was found to be slightly lower from the corresponding bulk value (n = 2.28). Various factors responsible for the deviation in the refractive index of (006) LiNbO 3 thin films from the corresponding bulk value are discussed and the deviation is mainly attributed to the lattice contraction due to the presence of stress in deposited film.

Coupling between magnetic and optical properties of stable Au-Fe solid solution nanoparticles

Energy Technology Data Exchange (ETDEWEB)

De Julian Fernandez, C; Novak, R L; Bogani, L; Caneschi, A [INSTM RU at the Department of Chemistry of the University of Firenze, via della Lastruccia 3, 50019 Sesto Fiorentino (Italy); Mattei, G; Mazzoldi, P [Department of Physics, CNISM and University of Padova, via Marzolo 8, 35131 Padova (Italy); Paz, E; Palomares, F J [Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, 28049 Madrid (Spain); Cavigli, L, E-mail: cesar.dejulian@unifi.it [Department of Physics-LENS, University of Florence, via Sansone 1, 50019 Sesto Fiorentino (Italy)

2010-04-23

Au-Fe nanoparticles constitute one of the simplest prototypes of a multifunctional nanomaterial that can exhibit both magnetic and optical (plasmonic) properties. This solid solution, not feasible in the bulk phase diagram in thermal equilibrium, can be formed as a nanostructure by out-of-equilibrium processes. Here, the novel magnetic, optical and magneto-optical properties of ion-implanted Au-Fe solid solution nanoparticles dispersed in a SiO{sub 2} matrix are investigated and correlated. The surface plasmon resonance of the Au-Fe nanoparticles with almost equicomposition is strongly damped when compared to pure Au and to Au-rich Au-Fe nanoparticles. In all cases, the Au atoms are magnetically polarized, as measured by x-ray magnetic circular dichroism, and ferromagnetically coupled with Fe atoms. Although the chemical stability of Au-Fe nanoparticles is larger than that of Fe nanoparticles, both the magnetic moment per Fe atom and the order temperature are smaller. These results suggest that electronic and magnetic properties are more influenced by the hybridization of the electronic bands in the Au-Fe solid solution than by size effects. On the other hand, the magneto-optical transitions allowed in the vis-nIR spectral regions are very similar. In addition, we also observe, after studying the properties of thermally treated samples, that the Au-Fe alloy is stabilized, not by surface effects, but by the combination of the out-of-equilibrium nature of the ion implantation technique and by changes in the properties due to size effects.

Coupling between magnetic and optical properties of stable Au-Fe solid solution nanoparticles

International Nuclear Information System (INIS)

De Julian Fernandez, C; Novak, R L; Bogani, L; Caneschi, A; Mattei, G; Mazzoldi, P; Paz, E; Palomares, F J; Cavigli, L

2010-01-01

Au-Fe nanoparticles constitute one of the simplest prototypes of a multifunctional nanomaterial that can exhibit both magnetic and optical (plasmonic) properties. This solid solution, not feasible in the bulk phase diagram in thermal equilibrium, can be formed as a nanostructure by out-of-equilibrium processes. Here, the novel magnetic, optical and magneto-optical properties of ion-implanted Au-Fe solid solution nanoparticles dispersed in a SiO 2 matrix are investigated and correlated. The surface plasmon resonance of the Au-Fe nanoparticles with almost equicomposition is strongly damped when compared to pure Au and to Au-rich Au-Fe nanoparticles. In all cases, the Au atoms are magnetically polarized, as measured by x-ray magnetic circular dichroism, and ferromagnetically coupled with Fe atoms. Although the chemical stability of Au-Fe nanoparticles is larger than that of Fe nanoparticles, both the magnetic moment per Fe atom and the order temperature are smaller. These results suggest that electronic and magnetic properties are more influenced by the hybridization of the electronic bands in the Au-Fe solid solution than by size effects. On the other hand, the magneto-optical transitions allowed in the vis-nIR spectral regions are very similar. In addition, we also observe, after studying the properties of thermally treated samples, that the Au-Fe alloy is stabilized, not by surface effects, but by the combination of the out-of-equilibrium nature of the ion implantation technique and by changes in the properties due to size effects.

Coupling between magnetic and optical properties of stable Au-Fe solid solution nanoparticles

Science.gov (United States)

de Julián Fernández, C.; Mattei, G.; Paz, E.; Novak, R. L.; Cavigli, L.; Bogani, L.; Palomares, F. J.; Mazzoldi, P.; Caneschi, A.

2010-04-01

Au-Fe nanoparticles constitute one of the simplest prototypes of a multifunctional nanomaterial that can exhibit both magnetic and optical (plasmonic) properties. This solid solution, not feasible in the bulk phase diagram in thermal equilibrium, can be formed as a nanostructure by out-of-equilibrium processes. Here, the novel magnetic, optical and magneto-optical properties of ion-implanted Au-Fe solid solution nanoparticles dispersed in a SiO2 matrix are investigated and correlated. The surface plasmon resonance of the Au-Fe nanoparticles with almost equicomposition is strongly damped when compared to pure Au and to Au-rich Au-Fe nanoparticles. In all cases, the Au atoms are magnetically polarized, as measured by x-ray magnetic circular dichroism, and ferromagnetically coupled with Fe atoms. Although the chemical stability of Au-Fe nanoparticles is larger than that of Fe nanoparticles, both the magnetic moment per Fe atom and the order temperature are smaller. These results suggest that electronic and magnetic properties are more influenced by the hybridization of the electronic bands in the Au-Fe solid solution than by size effects. On the other hand, the magneto-optical transitions allowed in the vis-nIR spectral regions are very similar. In addition, we also observe, after studying the properties of thermally treated samples, that the Au-Fe alloy is stabilized, not by surface effects, but by the combination of the out-of-equilibrium nature of the ion implantation technique and by changes in the properties due to size effects.

Mechanical properties of Fe-Ni-Cr-Si-B bulk glassy alloy

International Nuclear Information System (INIS)

Lee, Kee Ahn; Kim, Yong Chan; Kim, Jung Han; Lee, Chong Soo; Namkung, Jung; Kim, Moon Chul

2007-01-01

The mechanical properties and crystallization behavior of new Fe-Ni-Cr-Si-B-based bulk glassy alloys were investigated. The suitability of the continuous roll casting method for the production of bulk metallic glass (BMG) sheets in such alloy systems was also examined. BMG samples (Fe-Ni-Cr-Si-B, Fe-Ni-Zr-Cr-Si-B, Fe-Ni-Zr-Cr-W-Si-B) in amorphous strip, cylindrical, and sheet forms were prepared through melt spinning, copper mold casting, and twin roll strip casting, respectively. Fe-Ni-Cr-Si-B alloy exhibited compressive strength of up to 2.93 GPa and plastic strain of about 1.51%. On the other hand, the Fe-Ni-Zr-Cr-Si-B, composite-type bulk sample with diameter of 2.0 mm showed remarkable compressive plastic strain of about 4.03%. The addition of zirconium was found to enhance the homogeneous precipitation of nanocrystalline less than 7 nm and to develop a hybrid-composite microstructure with increasing sample thickness. Twin roll strip casting was successfully applied to the fabrication of sheets in Fe-Ni-Cr-Si-B-based BMGs. The combined characteristics of high mechanical properties and ease of microstructure control proved to be promising in terms of the future progress of structural bulk amorphous alloys

Mechanical properties of Fe-Ni-Cr-Si-B bulk glassy alloy

Energy Technology Data Exchange (ETDEWEB)

Lee, Kee Ahn [School of Advanced Materials Engineering, Andong National University, Andong 760-749 (Korea, Republic of)]. E-mail: keeahn@andong.ac.kr; Kim, Yong Chan [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of); Kim, Jung Han [Center for Advanced Aerospace materials, POSTECH, Pohang 790-784 (Korea, Republic of); Lee, Chong Soo [Center for Advanced Aerospace materials, POSTECH, Pohang 790-784 (Korea, Republic of); Namkung, Jung [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of); Kim, Moon Chul [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of)

2007-03-25

The mechanical properties and crystallization behavior of new Fe-Ni-Cr-Si-B-based bulk glassy alloys were investigated. The suitability of the continuous roll casting method for the production of bulk metallic glass (BMG) sheets in such alloy systems was also examined. BMG samples (Fe-Ni-Cr-Si-B, Fe-Ni-Zr-Cr-Si-B, Fe-Ni-Zr-Cr-W-Si-B) in amorphous strip, cylindrical, and sheet forms were prepared through melt spinning, copper mold casting, and twin roll strip casting, respectively. Fe-Ni-Cr-Si-B alloy exhibited compressive strength of up to 2.93 GPa and plastic strain of about 1.51%. On the other hand, the Fe-Ni-Zr-Cr-Si-B, composite-type bulk sample with diameter of 2.0 mm showed remarkable compressive plastic strain of about 4.03%. The addition of zirconium was found to enhance the homogeneous precipitation of nanocrystalline less than 7 nm and to develop a hybrid-composite microstructure with increasing sample thickness. Twin roll strip casting was successfully applied to the fabrication of sheets in Fe-Ni-Cr-Si-B-based BMGs. The combined characteristics of high mechanical properties and ease of microstructure control proved to be promising in terms of the future progress of structural bulk amorphous alloys.

Associations between the molecular and optical properties of dissolved organic matter in the Florida Everglades, a model coastal wetland system

Science.gov (United States)

Wagner, Sasha; Jaffe, Rudolf; Cawley, Kaelin; Dittmar, Thorsten; Stubbins, Aron

2015-11-01

Optical properties are easy-to-measure proxies for dissolved organic matter (DOM) composition, source and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows) and DOM sources (e.g., terrestrial, microbial and marine). As such, the Everglades is an excellent model system from which to draw samples of diverse origin and composition to allow classically-defined optical properties to be linked to molecular properties of the DOM pool. We characterized a suite of seasonally- and spatially-collected DOM samples using optical measurements (EEM-PARAFAC, SUVA254, S275-295, S350-400, SR, FI, freshness index and HIX) and ultrahigh resolution mass spectrometry (FTICR-MS). Spearman’s rank correlations between FTICR-MS signal intensities of individual molecular formulae and optical properties determined which molecular formulae were associated with each PARAFAC component and optical index. The molecular families that tracked with the optical indices were generally in agreement with conventional biogeochemical interpretations. Therefore, although they represent only a small portion of the bulk DOM pool, absorbance and fluorescence measurements appear to be appropriate proxies for the aquatic cycling of both optically-active and associated optically-inactive DOM in coastal wetlands.

Optical properties of solids

CERN Document Server

Wooten, Frederick

1972-01-01

Optical Properties of Solids covers the important concepts of intrinsic optical properties and photoelectric emission. The book starts by providing an introduction to the fundamental optical spectra of solids. The text then discusses Maxwell's equations and the dielectric function; absorption and dispersion; and the theory of free-electron metals. The quantum mechanical theory of direct and indirect transitions between bands; the applications of dispersion relations; and the derivation of an expression for the dielectric function in the self-consistent field approximation are also encompassed.

First-principles study of structural stability, electronic, optical and elastic properties of binary intermetallic: PtZr

Energy Technology Data Exchange (ETDEWEB)

Pagare, Gitanjali, E-mail: gita-pagare@yahoo.co.in [Department of Physics, Sarojini Naidu Government Girls P. G. Autonomous College, Bhopal-462016 (India); Jain, Ekta, E-mail: jainekta05@gmail.com [Department of Physics, Government M. L. B. Girls P. G. Autonomous College, Bhopal-462002 (India); Sanyal, S. P., E-mail: sps.physicsbu@gmail.com [Department of Physics, Barkatullah University, Bhopal-462026 (India)

2016-05-06

Structural, electronic, optical and elastic properties of PtZr have been studied using the full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). The energy against volume and enthalpy vs. pressure variation in three different structures i.e. B{sub 1}, B{sub 2} and B{sub 3} for PtZr has been presented. The equilibrium lattice parameter, bulk modulus and its pressure derivative have been obtained using optimization method for all the three phases. Furthermore, electronic structure was discussed to reveal the metallic character of the present compound. The linear optical properties are also studied under zero pressure for the first time. Results on elastic properties are obtained using generalized gradient approximation (GGA) for exchange correlation potentials. Ductile nature of PtZr compound is predicted in accordance with Pugh’s criteria.

Sintering Process and Mechanical Property of MWCNTs/HDPE Bulk Composite.

Science.gov (United States)

Ming-Wen, Wang; Tze-Chi, Hsu; Jie-Ren, Zheng

2009-08-01

Studies have proved that increasing polymer matrices by carbon nanotubes to form structural reinforcement and electrical conductivity have significantly improved mechanical and electrical properties at very low carbon nanotubes loading. In other words, increasing polymer matrices by carbon nanotubes to form structural reinforcement can reduce friction coefficient and enhance anti-wear property. However, producing traditional MWCNTs in polymeric materix is an extremely complicated process. Using melt-mixing process or in situ polymerization leads to better dispersion effect on composite materials. In this study, therefore, to simplify MWCNTs /HDPE composite process and increase dispersion, powder was used directly to replace pellet to mix and sinter with MWCNTs. The composite bulks with 0, 0.5, 1, 2 and 4% nanotube content by weight was analyzed under SEM to observe nanotubes dispersion. At this rate, a MWCNTs/HDPE composite bulk with uniformly dispersed MWCNTs was achieved, and through the wear bench (Pin-on-Disk), the wear experiment has accomplished. Accordingly, the result suggests the sintered MWCNTs/HDPE composites amplify the hardness and wear-resist property.

Climatology of Aerosol Optical Properties in Southern Africa

Science.gov (United States)

Queface, Antonio J.; Piketh, Stuart J.; Eck, Thomas F.; Tsay, Si-Chee

2011-01-01

A thorough regionally dependent understanding of optical properties of aerosols and their spatial and temporal distribution is required before we can accurately evaluate aerosol effects in the climate system. Long term measurements of aerosol optical depth, Angstrom exponent and retrieved single scattering albedo and size distribution, were analyzed and compiled into an aerosol optical properties climatology for southern Africa. Monitoring of aerosol parameters have been made by the AERONET program since the middle of the last decade in southern Africa. This valuable information provided an opportunity for understanding how aerosols of different types influence the regional radiation budget. Two long term sites, Mongu in Zambia and Skukuza in South Africa formed the core sources of data in this study. Results show that seasonal variation of aerosol optical thicknesses at 500 nm in southern Africa are characterized by low seasonal multi-month mean values (0.11 to 0.17) from December to May, medium values (0.20 to 0.27) between June and August, and high to very high values (0.30 to 0.46) during September to November. The spatial distribution of aerosol loadings shows that the north has high magnitudes than the south in the biomass burning season and the opposite in none biomass burning season. From the present aerosol data, no long term discernable trends are observable in aerosol concentrations in this region. This study also reveals that biomass burning aerosols contribute the bulk of the aerosol loading in August-October. Therefore if biomass burning could be controlled, southern Africa will experience a significant reduction in total atmospheric aerosol loading. In addition to that, aerosol volume size distribution is characterized by low concentrations in the non biomass burning period and well balanced particle size contributions of both coarse and fine modes. In contrast high concentrations are characteristic of biomass burning period, combined with

Electronic and optical properties of RESn{sub 3} (RE=Pr & Nd) intermetallics: A first principles study

Energy Technology Data Exchange (ETDEWEB)

Pagare, G., E-mail: gita-pagare@yahoo.co.in [Department of Physics, Government M. L. B. Girls P. G. Autonomous College, Bhopal-462002 (India); Abraham, Jisha A. [Department of Physics, Government M. L. B. Girls P. G. Autonomous College, Bhopal-462002 (India); Department of Physics, National Defence Academy, Pune-411023 (India); Sanyal, S. P. [Department of Physics, Barkatullah University, Bhopal-462026 (India)

2015-06-24

A theoretical study of structural, electronic and optical properties of RESn{sub 3} (RE = Pr & Nd) intermetallics have been investigated systematically using first principles density functional theory. The calculations are carried out within the PBE-GGA and LSDA for the exchange correlation potential. The ground state properties such as lattice parameter (a{sub 0}), bulk modulus (B) and its pressure derivative (B′) are calculated and the calculated lattice parameters show well agreement with the experimental results. We first time predict elastic constants for these compounds. From energy dispersion curves, it is found that these compounds are metallic in nature. The linear optical response of these compounds are also studied and the higher value of static dielectric constant shows the possibility to use them as good dielectric materials.

Theoretical investigation of electronic, magnetic and optical properties of Fe doped GaN thin films

International Nuclear Information System (INIS)

Salmani, E.; Mounkachi, O.; Ez-Zahraouy, H.; Benyoussef, A.; Hamedoun, M.; Hlil, E.K.

2013-01-01

Highlights: •Magnetic and optical properties Fe-doped GaN thin films are studied using DFT. •The band gaps of GaN thin films are larger than the one of the bulk. •The layer thickness and acceptor defect can switch the magnetic ordering. -- Abstract: Using first principles calculations based on spin-polarized density functional theory, the magnetic and optical properties of GaN and Fe-doped GaN thin films with and without acceptor defect is studied. The band structure calculations show that the band gaps of GaN thin films with 2, 4 and 6 layers are larger than the one of the bulk with wurtzite structure and decreases with increasing the film thickness. In Fe doped GaN thin films, we show that layer of thickness and acceptor defect can switch the magnetic ordering from disorder local moment (DLM) to ferromagnetic (FM) order. Without acceptor defect Fe doped GaN exhibits spin glass phase in 4 layers form and ferromagnetic state for 2 layers form of the thin films, while it exhibits ferromagnetic phase with acceptor defect such as vacancies defect for 2 and 4 layers. In the FM ordering, the thin films is half-metallic and is therefore ideal for spin application. The different energy between ferromagnetic state and disorder local moment state was evaluated. Moreover, the optical absorption spectra obtained by ab initio calculations confirm the ferromagnetic stability based on the charge state of magnetic impurities

Ultrafast dynamics in semiconductor optical amplifiers and all-optical processing: Bulk versus quantum dot devices

DEFF Research Database (Denmark)

Mørk, Jesper; Berg, Tommy Winther; Magnúsdóttir, Ingibjörg

2003-01-01

We discuss the dynamical properties of semiconductor optical amplifiers and the importance for all-optical signal processing. In particular, the dynamics of quantum dot amplifiers is considered and it is suggested that these may be operated at very high bit-rates without significant patterning...

Synthesis of formamidinium lead iodide perovskite bulk single crystal and its optical properties

Science.gov (United States)

Zheng, Hongge; Duan, Junjie; Dai, Jun

2017-07-01

Formamidinium lead iodide (FAPbI3) is a promising hybrid perovskite material for optoelectronic devices. We synthesized bulk single crystal FAPbI3 by a rapid solution crystallization method. X-ray diffraction (XRD) was performed to characterize the crystal structure. Temperature-dependent photoluminescence (PL) spectra of the bulk single crystal FAPbI3 were measured from 10 to 300 K to explain PL recombination mechanism. It shows that near band edge emission blueshifts with the temperature increasing from 10 to 120 K and from 140 K to room temperature, a sudden emission band redshift demonstrates near 140 K because of the phase transition from orthorhombic phase to cubic phase. From the temperature-dependent PL spectra, the temperature coefficients of the bandgap and thermal activation energies of FAPbI3 perovskite are fitted.

Computational Approach for Studying Optical Properties of DNA Systems in Solution

DEFF Research Database (Denmark)

Nørby, Morten Steen; Svendsen, Casper Steinmann; Olsen, Jógvan Magnus Haugaard

2016-01-01

In this paper we present a study of the methodological aspects regarding calculations of optical properties for DNA systems in solution. Our computational approach will be built upon a fully polarizable QM/MM/Continuum model within a damped linear response theory framework. In this approach...... the environment is given a highly advanced description in terms of the electrostatic potential through the polarizable embedding model. Furthermore, bulk solvent effects are included in an efficient manner through a conductor-like screening model. With the aim of reducing the computational cost we develop a set...... of averaged partial charges and distributed isotropic dipole-dipole polarizabilities for DNA suitable for describing the classical region in ground-state and excited-state calculations. Calculations of the UV-spectrum of the 2-aminopurine optical probe embedded in a DNA double helical structure are presented...

The electronic and optical properties of amorphous silica with hydrogen defects by ab initio calculations

Science.gov (United States)

Ren, Dahua; Xiang, Baoyan; Hu, Cheng; Qian, Kai; Cheng, Xinlu

2018-04-01

Hydrogen can be trapped in the bulk materials in four forms: interstitial molecular H2, interstitial atom H, O‑H+(2Si=O–H)+, Si‑H‑( {{4O}}\\bar \\equiv {{Si&x2212H}})‑ to affect the electronic and optical properties of amorphous silica. Therefore, the electronic and optical properties of defect-free and hydrogen defects in amorphous silica were performed within the scheme of density functional theory. Initially, the negative charged states hydrogen defects introduced new defect level between the valence band top and conduction band bottom. However, the neutral and positive charged state hydrogen defects made both the valence band and conduction band transfer to the lower energy. Subsequently, the optical properties such as absorption spectra, conductivity and loss functions were analyzed. It is indicated that the negative hydrogen defects caused the absorption peak ranging from 0 to 2.0 eV while the positive states produced absorption peaks at lower energy and two strong absorption peaks arose at 6.9 and 9.0 eV. However, the neutral hydrogen defects just improved the intensity of absorption spectrum. This may give insights into understanding the mechanism of laser-induced damage for optical materials. Project supported by the Science and Technology of Hubei Provincial Department of Education (No. B2017098).

Bulk plasma properties in the pulsed glow discharge

International Nuclear Information System (INIS)

Jackson, Glen P.; King, Fred L.

2003-01-01

This work focuses on the spatial and temporal characteristics of a glow discharge plasma operated with power pulses of 5 ms in duration at 25% duty cycle. Interpretation of emission data provides insight into the nature of the plasma at each instant of a typical pulse cycle and at each position in space. Because the bulk plasma properties affect the distribution of excited energy levels of the sputtered atoms, an improved understanding of the plasma affords the ability to select conditions that enhance analytically important emission lines. Optical emission spectroscopy was used to determine the relative populations of excited states for atoms and ions during the initial breakdown, the steady state and the recombining periods of the discharge pulse cycle. The plasma is highly ionizing in nature at the time of breakdown--with lower excited states being overpopulated--before reaching the steady state, or plateau, period, also ionizing in nature. These behaviors arise from a loss of charged particles and photons to the surroundings that shifts the plasma away from Saha and Boltzmann balances during these periods. The post-pulse period typically displays recombining behavior, characterized by population inversion for selected species--except for regions close to the cathode, where electrons and ions are lost by diffusion and are not available for recombination. The sputtered analyte atom emissions closely mimic those of the plasma bath gas, except that their emissions persevere for longer in the recombining after-peak period than do the discharge gas species

Evaluation of bulk and surfaces absorption edge energy of sol-gel-dip-coating SnO2 thin films

Directory of Open Access Journals (Sweden)

Emerson Aparecido Floriano

2010-12-01

Full Text Available The absorption edge and the bandgap transition of sol-gel-dip-coating SnO2 thin films, deposited on quartz substrates, are evaluated from optical absorption data and temperature dependent photoconductivity spectra. Structural properties of these films help the interpretation of bandgap transition nature, since the obtained nanosized dimensions of crystallites are determinant on dominant growth direction and, thus, absorption energy. Electronic properties of the bulk and (110 and (101 surfaces are also presented, calculated by means of density functional theory applied to periodic calculations at B3LYP hybrid functional level. Experimentally obtained absorption edge is compared to the calculated energy band diagrams of bulk and (110 and (101 surfaces. The overall calculated electronic properties in conjunction with structural and electro-optical experimental data suggest that the nature of the bandgap transition is related to a combined effect of bulk and (101 surface, which presents direct bandgap transition.

The relationship between structural and optical properties of Se-Ge-As glasses

Science.gov (United States)

Ghayebloo, M.; Rezvani, M.; Tavoosi, M.

2018-05-01

In this study, the structural and optical characterization of bulk Se-Ge-As glasses has been investigated. In this regards, six different Se60Ge40-xAsx (0 ≤ x ≤ 25) glasses were prepared by conventional melt quenching technique in quartz ampoule. The produced samples were characterized using X-ray diffraction (XRD), Raman spectroscopy, differential thermal analysis (DTA), ultraviolet-visible (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy. The fundamental absorption edge for all the glasses was analyzed in terms of the theory proposed by Davis and Mott. According to achieved results, fully amorphous phase can easily form in different Se-Ge-As systems. The thermal and optical characteristic of Se60Ge40-xAsx glasses shows anomalous behavior at 5 mol% of As for the glass transition temperature, transmittance, absorption edge, optical energy gap and Urbach energy. The highest glass transition temperature, transmittance, optical energy gap and Urbach energy properties were achieved in Se60Ge35As5 glass as a result of the highest connectivity of cations and anions in glass network.

"Peak tracking chip" for label-free optical detection of bio-molecular interaction and bulk sensing.

Science.gov (United States)

Bougot-Robin, Kristelle; Li, Shunbo; Zhang, Yinghua; Hsing, I-Ming; Benisty, Henri; Wen, Weijia

2012-10-21

A novel imaging method for bulk refractive index sensing or label-free bio-molecular interaction sensing is presented. This method is based on specially designed "Peak tracking chip" (PTC) involving "tracks" of adjacent resonant waveguide gratings (RWG) "micropads" with slowly evolving resonance position. Using a simple camera the spatial information robustly retrieves the diffraction efficiency, which in turn transduces either the refractive index of the liquids on the tracks or the effective thickness of an immobilized biological layer. Our intrinsically multiplex chip combines tunability and versatility advantages of dielectric guided wave biochips without the need of costly hyperspectral instrumentation. The current success of surface plasmon imaging techniques suggests that our chip proposal could leverage an untapped potential to routinely extend such techniques in a convenient and sturdy optical configuration toward, for instance for large analytes detection. PTC design and fabrication are discussed with challenging process to control micropads properties by varying their period (step of 2 nm) or their duty cycle through the groove width (steps of 4 nm). Through monochromatic imaging of our PTC, we present experimental demonstration of bulk index sensing on the range [1.33-1.47] and of surface biomolecule detection of molecular weight 30 kDa in aqueous solution using different surface densities. A sensitivity of the order of 10(-5) RIU for bulk detection and a sensitivity of the order of ∼10 pg mm(-2) for label-free surface detection are expected, therefore opening a large range of application of our chip based imaging technique. Exploiting and chip design, we expect as well our chip to open new direction for multispectral studies through imaging.

Associations between the molecular and optical properties of dissolved organic matter in the Florida Everglades, a model coastal wetland system

Directory of Open Access Journals (Sweden)

Sasha eWagner

2015-11-01

Full Text Available Optical properties are easy-to-measure proxies for dissolved organic matter (DOM composition, source and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows and DOM sources (e.g., terrestrial, microbial and marine. As such, the Everglades is an excellent model system from which to draw samples of diverse origin and composition to allow classically-defined optical properties to be linked to molecular properties of the DOM pool. We characterized a suite of seasonally- and spatially-collected DOM samples using optical measurements (EEM-PARAFAC, SUVA254, S275-295, S350-400, SR, FI, freshness index and HIX and ultrahigh resolution mass spectrometry (FTICR-MS. Spearman’s rank correlations between FTICR-MS signal intensities of individual molecular formulae and optical properties determined which molecular formulae were associated with each PARAFAC component and optical index. The molecular families that tracked with the optical indices were generally in agreement with conventional biogeochemical interpretations. Therefore, although they represent only a small portion of the bulk DOM pool, absorbance and fluorescence measurements appear to be appropriate proxies for the aquatic cycling of both optically-active and associated optically-inactive DOM in coastal wetlands.

Investigation on properties of ultrafast switching in a bulk gallium arsenide avalanche semiconductor switch

International Nuclear Information System (INIS)

Hu, Long; Su, Jiancang; Ding, Zhenjie; Hao, Qingsong; Yuan, Xuelin

2014-01-01

Properties of ultrafast switching in a bulk gallium arsenide (GaAs) avalanche semiconductor switch based on semi-insulating wafer, triggered by an optical pulse, were analyzed using physics-based numerical simulations. It has been demonstrated that when a voltage with amplitude of 5.2 kV is applied, after an exciting optical pulse with energy of 1 μJ arrival, the structure with thickness of 650 μm reaches a high conductivity state within 110 ps. Carriers are created due to photons absorption, and electrons and holes drift to anode and cathode terminals, respectively. Static ionizing domains appear both at anode and cathode terminals, and create impact-generated carriers which contribute to the formation of electron-hole plasma along entire channel. When the electric field in plasma region increases above the critical value (∼4 kV/cm) at which the electrons drift velocity peaks, a domain comes into being. An increase in carrier concentration due to avalanche multiplication in the domains reduces the domain width and results in the formation of an additional domain as soon as the field outside the domains increases above ∼4 kV/cm. The formation and evolution of multiple powerfully avalanching domains observed in the simulations are the physical reasons of ultrafast switching. The switch exhibits delayed breakdown with the characteristics affected by biased electric field, current density, and optical pulse energy. The dependence of threshold energy of the exciting optical pulse on the biased electric field is discussed

Infrared optical properties of a coal-fired power plant plume

International Nuclear Information System (INIS)

Stearns, L.P.; Pueschel, R.F.

1983-01-01

Infrared measurements in the 8--14-μm spectral region were made of two coal-fired power plant plumes and area haze in the Four Corners region of New Mexico from 1 to 7 Nov. 1980. The layer tranmittance, optical depth, and volume extinction coefficient derived from measurements on four nonconsecutive days show the effects of the plumes on the IR optical properties of the atmosphere. The average contribution of the plume alone to the IR extinction coefficient was 74% at the Four Corners plant; the background haze contributed 7--11%. More efficient particulate emission control at the San Juan power plant reduced the average contribution of its plume to 57% of the extinction coefficient. The haze contributed an average of 16%. The results show an increase with time of the haze bulk extinction coefficient during a persistent anticyclonic synoptic situation. Extinction coefficients of the haze showed a linearity with particulate loading, which led to estimates of IR volume extinctions of the free troposphre from aerosol measurements

Fabrication of Bi2223 bulks with high critical current properties sintered in Ag tubes

Energy Technology Data Exchange (ETDEWEB)

Takeda, Yasuaki, E-mail: ytakeda@g.ecc.u-tokyo.ac.jp [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Shimoyama, Jun-ichi; Motoki, Takanori [Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258 (Japan); Kishio, Kohji [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Nakashima, Takayoshi; Kagiyama, Tomohiro; Kobayashi, Shin-ichi; Hayashi, Kazuhiko [Sumitomo Electric Industries, Ltd. 1-1-3 Shimaya, Konohana-ku, Osaka 554-0024 (Japan)

2017-03-15

Highlights: • Fabrication conditions of Bi2223 bulks was reconsidered in terms of high J{sub c}. • Pressure of uniaxial pressing and heat treatment conditions were investigated. • The best sample showed higher J{sub c} than that of practically used Bi2223 bulks. - Abstract: Randomly grain oriented Bi2223 sintered bulks are one of the representative superconducting materials having weak-link problem due to very short coherence length particularly along the c-axis, resulting in poor intergrain J{sub c} properties. In our previous studies, sintering and/or post-annealing under moderately reducing atmospheres were found to be effective for improving grain coupling in Bi2223 sintered bulks. Further optimizations of the synthesis process for Bi2223 sintered bulks were attempted in the present study to enhance their intergrain J{sub c}. Effects of applied pressure of uniaxial pressing and sintering conditions on microstructure and superconducting properties have been systematically investigated. The best sample showed intergrain J{sub c} of 2.0 kA cm{sup −2} at 77 K and 8.2 kA cm{sup −2} at 20 K, while its relative density was low ∼65%. These values are quite high as for a randomly oriented sintered bulk of cuprate superconductors.

Evaluation of mechanical properties of Dy123 bulk superconductors by 3-point bending tests

International Nuclear Information System (INIS)

Katagiri, K.; Hatakeyama, Y.; Sato, T.; Kasaba, K.; Shoji, Y.; Murakami, A.; Teshima, H.; Hirano, H.

2006-01-01

In order to evaluate the mechanical properties, such as Young's modulus and strength, of Dy123 bulk superconductors and those with 10 wt.% Ag 2 O, we performed 3-point bending tests at room (RT) and liquid nitrogen temperatures (LNT) using specimens cut from the bulks. The Young's modulus and the bending strength increased with decrease in temperature. In the tests loading in the direction of c-axis and ones perpendicular to it, Young's moduli were almost comparable at both RT and LNT. Although the strengths for both orientations were also comparable at LNT, those at RT were different. Young's moduli loaded in the direction of c-axis for Ag 2 O added bulk specimens, 127 GPa in average at RT, were almost comparable to those without Ag 2 O, and 134 GPa at LNT, were slightly lower than those without Ag 2 O. On the other hand, the strengths at both RT and LNT were enhanced by 20% by the Ag addition. The mechanical properties of Dy123 bulks without Ag 2 O were compared with those of Y123 bulks obtained previously. The Young's modulus for loading in the direction of c-axis was slightly lower, and the strength was comparable to those in Y123 bulks, respectively

Mechanical and thermal properties of bulk ZrB{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Nakamori, Fumihiro [Graduate School of Engineering, Osaka University (Japan); Ohishi, Yuji, E-mail: ohishi@ms.see.eng.osaka-u.ac.jp [Graduate School of Engineering, Osaka University (Japan); Muta, Hiroaki; Kurosaki, Ken [Graduate School of Engineering, Osaka University (Japan); Fukumoto, Ken-ichi [Research Institute of Nuclear Engineering, University of Fukui (Japan); Yamanaka, Shinsuke [Graduate School of Engineering, Osaka University (Japan); Research Institute of Nuclear Engineering, University of Fukui (Japan)

2015-12-15

ZrB{sub 2} appears to have formed in the fuel debris at the Fukushima Daiichi nuclear disaster site, through the reaction between Zircaloy cladding materials and the control rod material B{sub 4}C. Since ZrB{sub 2} has a high melting point of 3518 K, the ceramic has been widely studied as a heat-resistant material. Although various studies on the thermochemical and thermophysical properties have been performed for ZrB{sub 2}, significant differences exist in the data, possibly due to impurities or the porosity within the studied samples. In the present study, we have prepared a ZrB{sub 2} bulk sample with 93.1% theoretical density by sintering ZrB{sub 2} powder. On this sample, we have comprehensively examined the thermal and mechanical properties of ZrB{sub 2} by the measurement of specific heat, ultrasonic sound velocities, thermal diffusivity, and thermal expansion. Vickers hardness and fracture toughness were also measured and found to be 13–23 GPa and 1.8–2.8 MPa m{sup 0.5}, respectively. The relationships between these properties were carefully examined in the present study. - Highlights: • A ZrB{sub 2} bulk sample with 93.1% theoretical density was prepared by sintering ZrB{sub 2} powder. • We have evaluated mechanical and thermal properties such as Vickers hardness, fracture toughness and thermal conductivity. • The relationships between these properties were carefully examined.

Multilayered phantoms with tunable optical properties for a better understanding of light/tissue interactions

Science.gov (United States)

Roig, Blandine; Koenig, Anne; Perraut, François; Piot, Olivier; Vignoud, Séverine; Lavaud, Jonathan; Manfait, Michel; Dinten, Jean-Marc

2015-03-01

Light/tissue interactions, like diffuse reflectance, endogenous fluorescence and Raman scattering, are a powerful means for providing skin diagnosis. Instrument calibration is an important step. We thus developed multilayered phantoms for calibration of optical systems. These phantoms mimic the optical properties of biological tissues such as skin. Our final objective is to better understand light/tissue interactions especially in the case of confocal Raman spectroscopy. The phantom preparation procedure is described, including the employed method to obtain a stratified object. PDMS was chosen as the bulk material. TiO2 was used as light scattering agent. Dye and ink were adopted to mimic, respectively, oxy-hemoglobin and melanin absorption spectra. By varying the amount of the incorporated components, we created a material with tunable optical properties. Monolayer and multilayered phantoms were designed to allow several characterization methods. Among them, we can name: X-ray tomography for structural information; Diffuse Reflectance Spectroscopy (DRS) with a homemade fibered bundle system for optical characterization; and Raman depth profiling with a commercial confocal Raman microscope for structural information and for our final objective. For each technique, the obtained results are presented and correlated when possible. A few words are said on our final objective. Raman depth profiles of the multilayered phantoms are distorted by elastic scattering. The signal attenuation through each single layer is directly dependent on its own scattering property. Therefore, determining the optical properties, obtained here with DRS, is crucial to properly correct Raman depth profiles. Thus, it would be permitted to consider quantitative studies on skin for drug permeation follow-up or hydration assessment, for instance.

Optical properties of organic semiconductor thin films. Static spectra and real-time growth studies

Energy Technology Data Exchange (ETDEWEB)

Heinemeyer, Ute

2009-07-20

The aim of this work was to establish the anisotropic dielectric function of organic thin films on silicon covered with native oxide and to study their optical properties during film growth. While the work focuses mainly on the optical properties of Diindenoperylene (DIP) films, also the optical response of Pentacene (PEN) films during growth is studied for comparison. Spectroscopic ellipsometry and differential reflectance spectroscopy are used to determine the dielectric function of the films ex-situ and in-situ, i.e. in air and in ultrahigh vacuum. Additionally, Raman- and fluorescence spectroscopy is utilized to characterize the DIP films serving also as a basis for spatially resolved optical measurements beyond the diffraction limit. Furthermore, X-ray reflectometry and atomic force microscopy are used to determine important structural and morphological film properties. The absorption spectrum of DIP in solution serves as a monomer reference. The observed vibronic progression of the HOMO-LUMO transition allows the determination of the Huang-Rhys parameter experimentally, which is a measure of the electronic vibrational coupling. The corresponding breathing modes are measured by Raman spectroscopy. The optical properties of DIP films on native oxide show significant differences compared to the monomer spectrum due to intermolecular interactions. First of all, the thin film spectra are highly anisotropic due to the structural order of the films. Furthermore the Frenkel exciton transfer is studied and the energy difference between Frenkel and charge transfer excitons is determined. Real-time measurements reveal optical differences between interfacial or surface molecules and bulk molecules that play an important role for device applications. They are not only performed for DIP films but also for PEN films. While for DIP films on glass the appearance of a new mode is visible, the spectra of PEN show a pronounced energy red-shift during growth. It is shown how the

Flux Trapping Properties of Bulk HIGH-TC Superconductors in Static Field-Cooling Magnetization

Science.gov (United States)

Deng, Z.; Tsuzuki, K.; Miki, M.; Felder, B.; Hara, S.; Izumi, M.

2013-06-01

The trapping process and saturation effect of trapped magnetic flux of bulk high-temperature superconductors by static field-cooling magnetization (FCM) are reported in the paper. With a cryogenic Bell Hall sensor attached on the center of the bulk surface, the synchronous magnetic signals were recorded during the whole magnetization process. It enables us to know the flux trapping behavior since the removal of the excitation field, as well as the subsequent flux relaxation phenomenon and the flux dissipation in the quench process of the bulk sample. With the help of flux mapping techniques, the relationship between the trapped flux and the applied field was further investigated; the saturation effect of trapped flux was discussed by comparing the peak trapped field and total magnetic flux of the bulk sample. These studies are useful to understand the basic flux trapping properties of bulk superconductors.

Emergent Low-Symmetry Phases and Large Property Enhancements in Ferroelectric KNbO ₃ Bulk Crystals

Energy Technology Data Exchange (ETDEWEB)

Lummen, Tom T. A. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 USA; Leung, J. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 USA; Kumar, Amit [School of Mathematics and Physics, Queen' s University Belfast, University Road, Belfast BT71NN Northern Ireland UK; Wu, X. [Department of Physics, University of Texas at Austin, Austin TX 78712 USA; Ren, Y. [Department of Physics, University of Texas at Austin, Austin TX 78712 USA; VanLeeuwen, Brian K. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 USA; Haislmaier, Ryan C. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 USA; Holt, Martin [Center for Nanoscale Materials, Argonne National Laboratory, Argonne IL 60439 USA; Lai, Keji [Department of Physics, University of Texas at Austin, Austin TX 78712 USA; Kalinin, Sergei V. [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA; Gopalan, Venkatraman [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 USA

2017-06-19

The design of new or enhanced functionality in materials is traditionally viewed as requiring the discovery of new chemical compositions through synthesis. Large property enhancements may however also be hidden within already well-known materials, when their structural symmetry is deviated from equilibrium through a small local strain or field. Here, the discovery of enhanced material properties associated with a new metastable phase of monoclinic symmetry within bulk KNbO3 is reported. This phase is found to coexist with the nominal orthorhombic phase at room temperature, and is both induced by and stabilized with local strains generated by a network of ferroelectric domain walls. While the local microstructural shear strain involved is only approximate to 0.017%, the concurrent symmetry reduction results in an optical second harmonic generation response that is over 550% higher at room temperature. Moreover, the meandering walls of the low-symmetry domains also exhibit enhanced electrical conductivity on the order of 1 S m(-1). This discovery reveals a potential new route to local engineering of significant property enhancements and conductivity through symmetry lowering in ferroelectric crystals.

Bulk monocrystal growth, optical, dielectric, third order nonlinear, thermal and mechanical studies on HCl added L-alanine: An organic NLO material

Energy Technology Data Exchange (ETDEWEB)

Shkir, Mohd, E-mail: shkirphysics@gmail.com [Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Physics Department, Faculty of Science, King Khalid University, Abha (Saudi Arabia); Yahia, I.S., E-mail: dr_isyahia@yahoo.com [Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Physics Department, Faculty of Science, King Khalid University, Abha (Saudi Arabia); Nano-Science & Semiconductor Labs, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Al-Qahtani, A.M.A. [Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Physics Department, Faculty of Science, King Khalid University, Abha (Saudi Arabia)

2016-12-01

In the current work, good quality bulk size (∼32 mm × 23 mm × 10 mm) single crystals of HCl added L-alanine with well-defined morphology are successfully grown using slow evaporation technique. Crystal structure and other structural parameters were evaluated from X-ray diffraction data. Vibrational assessment of the grown crystal was done by FT-Raman analysis. The presence of chlorine and good quality of the grown crystal was confirmed by SEM/EDX analysis. Solid state UV–Vis–NIR diffused reflectance was measured and direct and indirect optical band gap was calculated using Kubelka-Munk relation and found to be 5.64 and 5 eV respectively. Dielectric measurement was carried out in high frequency range. Third order nonlinear optical susceptibility value was found to be enhanced from 1.91 × 10{sup −6} (pure) to 8.6 × 10{sup −6} esu (LAHCl). Good thermal stability of grown crystals was confirmed from DSC analysis. The enhancement in mechanical strength and crystalline perfection was also observed. - Highlights: • Bulk size (32 mm × 23 mm × 10 mm), good crystalline perfection HCl added L-alanine monocrystal is grown. • The shift in X-ray diffraction and vibrational peaks confirms the interaction of HCl. • The high optical transparency and band gap confirms its application in optoelectronic devices. • Third order NLO properties are found to be enhanced in HCl added L-alanine crystals. • The mechanical strength of the grown crystals is found to be enhanced due HCl addition.

Effects of Germanium Tetrabromide Addition to Zinc Tetraphenyl Porphyrin / Fullerene Bulk Heterojunction Solar Cells

Directory of Open Access Journals (Sweden)

Atsushi Suzuki

2014-03-01

Full Text Available The effects of germanium tetrabromide addition to tetraphenyl porphyrin zinc (Zn-TPP/fullerene (C60 bulk heterojunction solar cells were characterized. The light-induced charge separation and charge transfer were investigated by current density and optical absorption. Addition of germanium tetrabromide inserted into active layer of Zn-TPP/C60 as bulk heterojunction had a positive effect on the photovoltaic and optical properties. The photovoltaic mechanism of the solar cells was discussed by experimental results. The photovoltaic performance was due to light-induced exciton promoted by insert of GeBr4 and charge transfer from HOMO of Zn-TPP to LUMO of C60 in the active layer.

Thermal, spectral, and surface properties of LED light-polymerized bulk fill resin composites.

Science.gov (United States)

Pişkin, Mehmet Burçin; Atalı, Pınar Yılmaz; Figen, Aysel Kantürk

2015-02-01

The aim of this study was to evaluate the thermal, spectral, and surface properties of four different bulk fill materials – SureFil SDR (SDR, Dentsplay DETREY), QuixFil (QF, Dentsplay DETREY), X-tra base (XB, Voco) X-tra fil (XF, Voco) – polymerized by light-emitting diode (LED). Resin matrix, filler type, size and amount, and photoinitiator types influence the degree of conversion. LED-cured bulk fill composites achieved sufficient polymerization. Scanning electron microscope (SEM) analysis revealed different patterns of surface roughness, depending on the composite material. Bulk fill materials showed surface characteristics similar to those of nanohybrid composites. Based on the thermal analysis results, glass transition (T(g)) and initial degradation (T(i)) temperatures changed depending on the bulk fill resin composites.

Reference dataset of volcanic ash physicochemical and optical properties for atmospheric measurement retrievals and transport modelling

Science.gov (United States)

Vogel, Andreas; Durant, Adam; Sytchkova, Anna; Diplas, Spyros; Bonadonna, Costanza; Scarnato, Barbara; Krüger, Kirstin; Kylling, Arve; Kristiansen, Nina; Stohl, Andreas

2016-04-01

Explosive volcanic eruptions emit up to 50 wt.% (total erupted mass) of fine ash particles (estimates of the volcanic source term and the nature of the constituent volcanic ash properties. Consequently, it is important to include a quantitative assessment of measurement uncertainties of ash properties to provide realistic ash forecast uncertainty. Currently, information on volcanic ash physicochemical and optical properties is derived from a small number of somewhat dated publications. In this study, we provide a reference dataset for physical (size distribution and shape), chemical (bulk vs. surface chemistry) and optical properties (complex refractive index in the UV-vis-NIR range) of a representative selection of volcanic ash samples from 10 different volcanic eruptions covering the full variability in silica content (40-75 wt.% SiO2). Through the combination of empirical analytical methods (e.g., image analysis, Energy Dispersive Spectroscopy, X-ray Photoelectron Spectroscopy, Transmission Electron Microscopy and UV/Vis/NIR/FTIR Spectroscopy) and theoretical models (e.g., Bruggeman effective medium approach), it was possible to fully capture the natural variability of ash physicochemical and optical characteristics. The dataset will be applied in atmospheric measurement retrievals and atmospheric transport modelling to determine the sensitivity to uncertainty in ash particle characteristics.

Synthesis of Cu2O from CuO thin films: Optical and electrical properties

Directory of Open Access Journals (Sweden)

Dhanya S. Murali

2015-04-01

Full Text Available Hole conducting, optically transparent Cu2O thin films on glass substrates have been synthesized by vacuum annealing (5×10−6 mbar at 700 K for 1 hour of magnetron sputtered (at 300 K CuO thin films. The Cu2O thin films are p-type and show enhanced properties: grain size (54.7 nm, optical transmission 72% (at 600 nm and Hall mobility 51 cm2/Vs. The bulk and surface Valence band spectra of Cu2O and CuO thin films are studied by temperature dependent Hall effect and Ultra violet photo electron Spectroscopy (UPS. CuO thin films show a significant band bending downwards (due to higher hole concentration than Cu2O thin films.

Using molecular mechanics to predict bulk material properties of fibronectin fibers.

Directory of Open Access Journals (Sweden)

Mark J Bradshaw

Full Text Available The structural proteins of the extracellular matrix (ECM form fibers with finely tuned mechanical properties matched to the time scales of cell traction forces. Several proteins such as fibronectin (Fn and fibrin undergo molecular conformational changes that extend the proteins and are believed to be a major contributor to the extensibility of bulk fibers. The dynamics of these conformational changes have been thoroughly explored since the advent of single molecule force spectroscopy and molecular dynamics simulations but remarkably, these data have not been rigorously applied to the understanding of the time dependent mechanics of bulk ECM fibers. Using measurements of protein density within fibers, we have examined the influence of dynamic molecular conformational changes and the intermolecular arrangement of Fn within fibers on the bulk mechanical properties of Fn fibers. Fibers were simulated as molecular strands with architectures that promote either equal or disparate molecular loading under conditions of constant extension rate. Measurements of protein concentration within micron scale fibers using deep ultraviolet transmission microscopy allowed the simulations to be scaled appropriately for comparison to in vitro measurements of fiber mechanics as well as providing estimates of fiber porosity and water content, suggesting Fn fibers are approximately 75% solute. Comparing the properties predicted by single molecule measurements to in vitro measurements of Fn fibers showed that domain unfolding is sufficient to predict the high extensibility and nonlinear stiffness of Fn fibers with surprising accuracy, with disparately loaded fibers providing the best fit to experiment. This work shows the promise of this microstructural modeling approach for understanding Fn fiber properties, which is generally applicable to other ECM fibers, and could be further expanded to tissue scale by incorporating these simulated fibers into three dimensional

Optical properties of the c-axis oriented LiNbO{sub 3} thin film

Energy Technology Data Exchange (ETDEWEB)

Shandilya, Swati; Sharma, Anjali [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Tomar, Monika [Miranda House, University of Delhi, Delhi 110007 (India); Gupta, Vinay, E-mail: drguptavinay@gmail.com [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India)

2012-01-01

C-axis oriented Lithium Niobate (LiNbO{sub 3}) thin films have been deposited onto epitaxially matched (001) sapphire substrate using pulsed laser deposition technique. Structural and optical properties of the thin films have been studied using the X-ray diffraction (XRD) and UV-Visible spectroscopy respectively. Raman spectroscopy has been used to study the optical phonon modes and defects in the c-axis oriented LiNbO{sub 3} thin films. XRD analysis indicates the presence of stress in the as-grown LiNbO{sub 3} thin films and is attributed to the small lattice mismatch between LiNbO{sub 3} and sapphire. Refractive index (n = 2.13 at 640 nm) of the (006) LiNbO{sub 3} thin films was found to be slightly lower from the corresponding bulk value (n = 2.28). Various factors responsible for the deviation in the refractive index of (006) LiNbO{sub 3} thin films from the corresponding bulk value are discussed and the deviation is mainly attributed to the lattice contraction due to the presence of stress in deposited film.

Electronic properties of wurtzite-phase InP nanowires determined by optical and magneto-optical spectroscopy

Science.gov (United States)

De Luca, Marta; Polimeni, Antonio

2017-12-01

Thanks to their peculiar shape and dimensions, semiconductor nanowires (NWs) are emerging as building components of novel devices. The presence of wurtzite (WZ) phase in the lattice structure of non-nitride III-V NWs is one of the most surprising findings in these nanostructures: this phase, indeed, cannot be found in the same materials in the bulk form, where the zincblende (ZB) structure is ubiquitous, and therefore the WZ properties are poorly known. This review focuses on WZ InP NWs, because growth techniques have reached a high degree of control on the structural properties of this material, and optical studies performed on high-quality samples have allowed determining the most useful electronic properties, which are reviewed here. After an introduction summarizing the reasons for the interest in WZ InP nanowires (Sec. I), we give an overview on growth process and structural and optical properties of WZ InP NWs (Sec. II). In Sec. III, a complete picture of the energy and symmetry of the lowest-energy conduction and valence bands, as assessed by polarization-resolved photoluminescence (PL) and photoluminescence-excitation (PLE) studies is drawn and compared to all the available theoretical information. The elastic properties of WZ InP (determined by PL under hydrostatic pressure) and the radiative recombination dynamics of spatially direct and indirect (namely, occurring across the WZ/ZB interfaces) transitions are also discussed. Section IV, focuses on the magneto-optical studies of WZ InP NWs. The diagram of the energy levels of excitons in WZ materials—with and without magnetic field—is first provided. Then, all theoretical and experimental information available about the changes in the transport properties (i.e., carrier effective mass) caused by the ZB→WZ phase variation are reviewed. Different NW/magnetic field geometrical configurations, sensitive to polarization selection rules, highlight anisotropies in the diamagnetic shifts, Zeeman splitting

Elaboration of optical glass-ceramic for frequency doubling

International Nuclear Information System (INIS)

Vigouroux, H.

2012-01-01

The High power laser development required the need of materials with nonlinear properties. Glass materials can be considered as ideal materials as they can be transparent and elaborated in very large dimension. Precipitation of non-centro symmetric crystalline particles in bulk glass leads to a material with bulk nonlinear properties. This glass-ceramic should be then easily integrated in such laser facilities. In this thesis, the results concerning the precipitation of the phase LiNbO 3 in the glassy-matrix 35 Li 2 O - 25 Nb 2 O 5 - 40 SiO 2 are detailed. The crystallization mechanism of this phase is studied through thermal analysis, optical and electronic microscopy as well as in-situ analyses. These studies reveal glass-ceramics are obtained through a precipitation of the lithium niobate crystalline phase in spherulite shape. The nonlinear optical properties are investigated on this materials and an original, isotropic Second Harmonic Generation Signal (SHG) is registered in the bulk glass-ceramic. A complete study using a multi-scale approach allows the correlation between the spherulite structure and the nonlinear optical properties. A mechanism at the origin of the SHG signal is proposed. This leads to a new approach for transparent inorganic materials development for isotropic SHG conversion. (author) [fr

Synthesis, characterization and optical properties of hybridized CdS-PVA nanocomposites

International Nuclear Information System (INIS)

Wang Hongmei; Chen Zhe; Fang Pengfei; Wang Shaojie

2007-01-01

Hybrid nanocomposites of CdS nanoparticles embedded in poly(vinyl alcohol)(PVA) matrixes had been prepared and characterized. The -OH groups acted as the coordination sites for cadmium ion aggregations and nanosized CdS particles were successfully grown in situ at these sites with the release of S 2- ions from thioacetamide. The density and size of the nanoparticles were found to be a function of molar quantity of cadmium ion used. X-ray diffraction results showed that the obtained CdS nanoparticles were hexagonal phase. Ionic clustering within the PVA matrix occurred and had provided a confined medium for particles growth in uniform size. The optical properties of the prepared CdS-PVA hybrid nanocomposites were characterized by absorption and emission spectroscopies. The absorption spectra showed a blue shift as compared to bulk CdS band-gap. The photoluminescence studies indicated the emission peak observed in samples could be assigned to the optical transition of the first excitonic state of the CdS nanoparticles

Temperature dependence of morphology, structural and optical properties of ZnS nanostructures synthesized by wet chemical route

International Nuclear Information System (INIS)

Navaneethan, M.; Archana, J.; Nisha, K.D.; Hayakawa, Y.; Ponnusamy, S.; Muthamizhchelvan, C.

2010-01-01

Research highlights: → ZnS nanoparticles and nanorods have been synthesized by wet chemical route. → Higher annealing temperature influenced the change in morphology due to aggregation of the nanoparticles. → The temperature dependent optical properties were investigated. → Absorption edge of nanoparticles (295 nm) and nanorods (326 nm) were shifted towards shorter wavelength compared to bulk ZnS (337 nm) due to the quantum confinement effect. → ZnS nanoparticles exhibit high photoluminescence intensity than that of ZnS nanorods annealed at 180 o C. - Abstract: ZnS nanostructures have been synthesized by simple wet chemical route and annealed at two different temperatures of 50 o C and 180 o C. From the measurements of transmission electron microscopy and contact-mode atomic force microscopy, it is found that annealed temperature changes the morphology from nanoparticles to nanorods. The optical properties of the synthesized ZnS nanomaterial have been characterized by UV-visible absorption spectroscopy and photoluminescence spectroscopy. The structural and elemental analyses were carried out by powder X-ray diffraction pattern and energy dispersive X-ray absorption spectroscopy, respectively. Absorption edge of the nanoparticles (295 nm) and nanorods (326 nm) was shifted towards shorter wavelength compared to bulk ZnS (337 nm) due to the quantum confinement effect.

Radiative properties of optical board embedded with optical black holes

International Nuclear Information System (INIS)

Qiu, J.; Liu, L.H.; Hsu, P.-F.

2011-01-01

Unique radiative properties, such as wavelength-selective transmission or absorption, have been intensively studied. Historically, geometries for wavelength-selective of light absorption were developed based on metallic periodical structures, which were only applied in the case of TM wave incidence due to the excitation of surface plasmons. In this paper, we develop an alternative approach to selective wavelength of light absorption (both TE and TM waves), based on an optical board periodical embedded with optical black holes. Numerical work was carried out to study such structure's radiative properties within the wavelength range of 1-100 μm. The electromagnetic wave transmission through such a structure is predicted by solving Maxwell's equations using the finite-difference time-domain (FDTD) method. Spectral absorptance varies with the period of optical black holes. When the incidence wavelength is much larger than the inner core radius, most of the light energy will be transmitted through the inner core. Otherwise, the energy will be mainly absorbed. Numerical results of the radiative properties of the optical board with different incidence wavelengths are also obtained. The effect of the oblique incidence wave is investigated. This study helps us gain a better understanding of the radiative properties of an optical board embedded with optical black holes and develop an alternative approach to selective light absorption.

Poly(methyl methacrylate)/layered zinc sulfide nanocomposites: Preparation, characterization and the improvements in thermal stability, flame retardant and optical properties

Energy Technology Data Exchange (ETDEWEB)

Wang, Biao; Zhou, Keqing; Jiang, Saihua [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Shi, Yongqian [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, 166 Ren’ai Road, Suzhou, Jiangsu 215123 (China); Wang, Bibo [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Gui, Zhou, E-mail: zgui@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Hu, Yuan, E-mail: yuanhu@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, 166 Ren’ai Road, Suzhou, Jiangsu 215123 (China)

2014-08-15

Highlights: • Layered zinc sulfide (LZnS) was synthesized successfully via hydrothermal method. • We prepare PMMA/LZnS nanocomposites by in situ bulk polymerization of MMA. • PMMA/LZnS nanocomposites were investigated by TGA, DSC, MCC, UV–vis and PL test. • The thermal stability, flame retardant and optical properties of PMMA are improved. - Abstract: Layered zinc sulfide (LZnS) was synthesized successfully via hydrothermal method and poly(methyl methacrylate) (PMMA)/layered zinc sulfide nanocomposites were obtained by in situ bulk polymerization of methyl methacrylate (MMA). X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the as-synthesized layered zinc sulfide and PMMA/layered zinc sulfide nanocomposites. Microscale combustion calorimeter (MCC), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) were used to test the thermal properties of the composites. Ultraviolet visible (UV–vis) transmittance spectra and photoluminence (PL) spectra were obtained to investigate the optical properties of the composites. From the results, the thermal degradation temperature is increased by 20–50 °C, the peak of heat release rate (pHRR) and total heat release (THR) are both decreased by above 30%, and the photoluminence intensity is enhanced with the increasing loading of layered zinc sulfide.

Poly(methyl methacrylate)/layered zinc sulfide nanocomposites: Preparation, characterization and the improvements in thermal stability, flame retardant and optical properties

International Nuclear Information System (INIS)

Wang, Biao; Zhou, Keqing; Jiang, Saihua; Shi, Yongqian; Wang, Bibo; Gui, Zhou; Hu, Yuan

2014-01-01

Highlights: • Layered zinc sulfide (LZnS) was synthesized successfully via hydrothermal method. • We prepare PMMA/LZnS nanocomposites by in situ bulk polymerization of MMA. • PMMA/LZnS nanocomposites were investigated by TGA, DSC, MCC, UV–vis and PL test. • The thermal stability, flame retardant and optical properties of PMMA are improved. - Abstract: Layered zinc sulfide (LZnS) was synthesized successfully via hydrothermal method and poly(methyl methacrylate) (PMMA)/layered zinc sulfide nanocomposites were obtained by in situ bulk polymerization of methyl methacrylate (MMA). X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the as-synthesized layered zinc sulfide and PMMA/layered zinc sulfide nanocomposites. Microscale combustion calorimeter (MCC), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) were used to test the thermal properties of the composites. Ultraviolet visible (UV–vis) transmittance spectra and photoluminence (PL) spectra were obtained to investigate the optical properties of the composites. From the results, the thermal degradation temperature is increased by 20–50 °C, the peak of heat release rate (pHRR) and total heat release (THR) are both decreased by above 30%, and the photoluminence intensity is enhanced with the increasing loading of layered zinc sulfide

The influence of ytterbium doping on the optical properties of tellurite glasses

Energy Technology Data Exchange (ETDEWEB)

Jaglarz, Janusz; Burtan, Bozena [Institute of Physics, Cracow University of Technology, ul. Podchorazych 1, 30-084 Cracow (Poland); Reben, Manuela; Wasylak, Jan [Faculty of Materials Science and Ceramics, AGH - University of Science and Technology, al. Mickiewicza 30, 30-059 Cracow (Poland); Cisowski, Jan [Institute of Physics, Cracow University of Technology, ul. Podchorazych 1, 30-084 Cracow (Poland); Centre of Polymer and Carbon Materials, Polish Academy of Sciences, ul. M. Curie-Sklodowskiej 34, 41-819 Zabrze (Poland); Jarzabek, Bozena [Centre of Polymer and Carbon Materials, Polish Academy of Sciences, ul. M. Curie-Sklodowskiej 34, 41-819 Zabrze (Poland)

2011-09-15

The goal of this work was to investigate the influence of rare earth ion Yb{sup 3+} doping on the thermal and optical properties of tellurite glass (TG) of the TeO{sub 2}-ZnO-PbO-La{sub 2}O{sub 3} system. The reflectance, transmittance and ellipsometric measurements have been done. Decreasing of the refractive index of TG with the Yb{sup 3+} ion doping has been concluded. For determination of the refractive index variation in the bulk, the small angle light scatter (SALS) measurements have been carried out. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Effective Optical Properties of Plasmonic Nanocomposites

Directory of Open Access Journals (Sweden)

Christoph Etrich

2014-01-01

Full Text Available Plasmonic nanocomposites find many applications, such as nanometric coatings in emerging fields, such as optotronics, photovoltaics or integrated optics. To make use of their ability to affect light propagation in an unprecedented manner, plasmonic nanocomposites should consist of densely packed metallic nanoparticles. This causes a major challenge for their theoretical description, since the reliable assignment of effective optical properties with established effective medium theories is no longer possible. Established theories, e.g., the Maxwell-Garnett formalism, are only applicable for strongly diluted nanocomposites. This effective description, however, is a prerequisite to consider plasmonic nanocomposites in the design of optical devices. Here, we mitigate this problem and use full wave optical simulations to assign effective properties to plasmonic nanocomposites with filling fractions close to the percolation threshold. We show that these effective properties can be used to properly predict the optical action of functional devices that contain nanocomposites in their design. With this contribution we pave the way to consider plasmonic nanocomposites comparably to ordinary materials in the design of optical elements.

Bulk and mechanical properties of the Paintbrush tuff recovered from borehole USW NRG-6: Data report

International Nuclear Information System (INIS)

Martin, R.J.; Boyd, P.J.; Noel, J.S.; Price, R.H.

1994-11-01

Experimental results are presented for bulk and mechanical properties measurements on specimens of the Paintbrush tuff recovered from borehole USW NRG-6 at Yucca Mountain, Nevada. Measurements have been performed on four thermal/mechanical units, TCw, PTn, TSw1 and TSw2. On each specimen the following bulk properties have been reported: dry bulk density, saturated bulk density, average grain density, and porosity. Unconfined compression to failure, confined compression to failure, and indirect tensile strength tests were performed on selected specimens recovered from the borehole. In addition, compressional and shear wave velocities were measured on specimens designated for unconfined compression and confined compression experiments. Measurements were conducted at room temperature on nominally water saturated specimens; however, some specimens of PTn were tested in a room dry condition. The nominal strain rate for the fracture experiments was 10 -5 s -1

Synthesis and characterization of NiO nanoparticles by thermal decomposition of nickel linoleate and their optical properties

Energy Technology Data Exchange (ETDEWEB)

Kalam, Abul, E-mail: abul_k33@yahoo.com [Department of Chemistry, Faculty of Science, King Khalid University, Abha 61413, P.O. Box 9004 (Saudi Arabia); Al-Sehemi, Abdullah G.; Al-Shihri, Ayed S. [Department of Chemistry, Faculty of Science, King Khalid University, Abha 61413, P.O. Box 9004 (Saudi Arabia); Du Gaohui [Zhejiang Key Laboratory for Reactive Chemistry on Solid Surfaces, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004 (China); Ahmad, Tokeer [Nanochemistry Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025 (India)

2012-06-15

Well dispersed nickel oxide nanoparticles have been synthesized successfully by direct calcination of nickel linoleate. The structure, morphology and properties of the nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and ultraviolet-visible spectroscopy. Transmission electron microscopic studies show that nickel oxide nanoparticles are uniform with an average size of 14-20 nm. The optical band gap of 3.8 eV is obtained using UV-Visible spectroscopy which exhibits the red shift compared with the bulk counterpart. - Highlights: Black-Right-Pointing-Pointer Synthesis of metal oxide nanoparticles by using metal complexes as precursors. Black-Right-Pointing-Pointer Characterization of isolated nanoparticles using XRD, FTIR, SEM, TEM and HRTEM data. Black-Right-Pointing-Pointer The expected optical properties of these nanoparticles are clarified.

Effect of oxygen vacancies on the electronic and optical properties of tungsten oxide from first principles calculations

Science.gov (United States)

Mehmood, Faisal; Pachter, Ruth; Murphy, Neil R.; Johnson, Walter E.; Ramana, Chintalapalle V.

2016-12-01

In this work, we investigated theoretically the role of oxygen vacancies on the electronic and optical properties of cubic, γ-monoclinic, and tetragonal phases of tungsten oxide (WO3) thin films. Following the examination of structural properties and stability of the bulk tungsten oxide polymorphs, we analyzed band structures and optical properties, applying density functional theory (DFT) and GW (Green's (G) function approximation with screened Coulomb interaction (W)) methods. Careful benchmarking of calculated band gaps demonstrated the importance of using a range-separated functional, where results for the pristine room temperature γ-monoclinic structure indicated agreement with experiment. Further, modulation of the band gap for WO3 structures with oxygen vacancies was quantified. Dielectric functions for cubic WO3, calculated at both the single-particle, essentially time-dependent DFT, as well as many-body GW-Bethe-Salpeter equation levels, indicated agreement with experimental data for pristine WO3. Interestingly, we found that introducing oxygen vacancies caused appearance of lower energy absorptions. A smaller refractive index was indicated in the defective WO3 structures. These predictions could lead to further experiments aimed at tuning the optical properties of WO3 by introducing oxygen vacancies, particularly for the lower energy spectral region.

Thermal properties of superconducting bulk metallic glasses at ultralow temperatures

International Nuclear Information System (INIS)

Rothfuss, Daniel Simon

2013-01-01

This thesis describes the first investigation of thermal properties of superconducting bulk metallic glasses in the range between 6mK and 300K. Measuring the thermal conductivity provides the possibility to probe the fundamental interactions governing the heat flow in solids. At ultralow temperatures a novel contactless measuring technique was used, which is based on optical heating and paramagnetic temperature sensors that are read out by a SQUID magnetometer. Below the critical temperature T c the results can be described by resonant scattering of phonons by tunneling systems. Above T c the phonon contribution to the thermal conductivity can be described successfully within a model considering not only electrons and phonons but also localized modes as scattering centres. To expand the accessible temperature range for experiments an adiabatic nuclear demagnetization refrigerator was set up. For measuring the base temperature a novel noise thermometer was developed which enables continuous measuring of the temperature in this temperature range for the first time. Therefore the magnetic Johnson noise of a massive copper cylinder is simultaneously monitored by two SQUID magnetometers. A subsequent cross-correlation suppresses the amplifier noise by more than one order of magnitude. The thermometer was characterized between 42μK and 0.8K showing no deviation from the expected linear behaviour between the power spectral density of the thermal noise and the temperature.

Double stage crystallization of bulk Ge20Te80 glass

International Nuclear Information System (INIS)

Parthasarathy, G.; Bandyopadhyay, A.K.; Gopal, E.S.R.; Subbanna, G.N.

1984-01-01

The growing interest of the semiconducting glasses is partly because of their interesting electrical and optical properties. These properties are usually connected with their crystallization. In many glasses, the glass-supercooled liquid transition precedes crystallization. The glass transition temperature (Tsub(g)) is found to exhibit multistage processes for a few systems. In this communication, we report the observation of a double Tsub(g) effect in bulk Ge 20 Te 80 glass and also explain the structural changes taking place in the two stages. (author)

Separating Bulk and Surface Contributions to Electronic Excited-State Processes in Hybrid Mixed Perovskite Thin Films via Multimodal All-Optical Imaging.

Science.gov (United States)

Simpson, Mary Jane; Doughty, Benjamin; Das, Sanjib; Xiao, Kai; Ma, Ying-Zhong

2017-07-20

A comprehensive understanding of electronic excited-state phenomena underlying the impressive performance of solution-processed hybrid halide perovskite solar cells requires access to both spatially resolved electronic processes and corresponding sample morphological characteristics. Here, we demonstrate an all-optical multimodal imaging approach that enables us to obtain both electronic excited-state and morphological information on a single optical microscope platform with simultaneous high temporal and spatial resolution. Specifically, images were acquired for the same region of interest in thin films of chloride containing mixed lead halide perovskites (CH 3 NH 3 PbI 3-x Cl x ) using femtosecond transient absorption, time-integrated photoluminescence, confocal reflectance, and transmission microscopies. Comprehensive image analysis revealed the presence of surface- and bulk-dominated contributions to the various images, which describe either spatially dependent electronic excited-state properties or morphological variations across the probed region of the thin films. These results show that PL probes effectively the species near or at the film surface.

Size-dependent optical properties of colloidal PbS quantum dots.

Science.gov (United States)

Moreels, Iwan; Lambert, Karel; Smeets, Dries; De Muynck, David; Nollet, Tom; Martins, José C; Vanhaecke, Frank; Vantomme, André; Delerue, Christophe; Allan, Guy; Hens, Zeger

2009-10-27

We quantitatively investigate the size-dependent optical properties of colloidal PbS nanocrystals or quantum dots (Qdots), by combining the Qdot absorbance spectra with detailed elemental analysis of the Qdot suspensions. At high energies, the molar extinction coefficient epsilon increases with the Qdot volume d(3) and agrees with theoretical calculations using the Maxwell-Garnett effective medium theory and bulk values for the Qdot dielectric function. This demonstrates that quantum confinement has no influence on epsilon in this spectral range, and it provides an accurate method to calculate the Qdot concentration. Around the band gap, epsilon only increases with d(1.3), and values are comparable to the epsilon of PbSe Qdots. The data are related to the oscillator strength f(if) of the band gap transition and results agree well with theoretical tight-binding calculations, predicting a linear dependence of f(if) on d. For both PbS and PbSe Qdots, the exciton lifetime tau is calculated from f(if). We find values ranging between 1 and 3 mus, in agreement with experimental literature data from time-resolved luminescence spectroscopy. Our results provide a thorough general framework to calculate and understand the optical properties of suspended colloidal quantum dots. Most importantly, it highlights the significance of the local field factor in these systems.

Copper phthalocyanine and metal free phthalocyanine bulk heterojunction photodetector

Energy Technology Data Exchange (ETDEWEB)

Farooq, Amjad, E-mail: amjad.farooq1212@hotmail.com [Wah Engineering College, University of Wah, Wah Cantt. 47040 (Pakistan); GIK Institute of Engineering Sciences and Technology, Topi 23640, Swabi (Pakistan); Karimov, Kh.S. [GIK Institute of Engineering Sciences and Technology, Topi 23640, Swabi (Pakistan); Physical Technical Institute, Aini St. 299/1, Dushanbe 734063 (Tajikistan); Ahmed, Nisar; Ali, Taimoor [GIK Institute of Engineering Sciences and Technology, Topi 23640, Swabi (Pakistan); Khalid Alamgir, M. [National Institute of Vacuum Science and Technology, NCP complex, Islamabad 44000 (Pakistan); Usman, Muhammad [Experimental Physics Laboratories, National Centre for Physics, Quaid-i-Azam University, Islamabad 44000 (Pakistan)

2015-01-15

In this study we present the dependence of electrical properties of copper phthalocyanine (CuPc) and metal free phthalocyanine (H{sub 2}Pc) bulk heterojunction structure under different illumination levels. To fabricate the device on ITO coated glass substrate the bulk heterojunction thin film of CuPc and H{sub 2}Pc with thickness varying from 100 nm to 300 nm are deposited by thermal evaporator. Aluminum thin film was deposited by thermal evaporation as a top contact. The optical properties of the fabricated device are investigated using UV–vis spectroscopy. The current-voltage characteristics in dark and under illumination show that the device is sensitive towards visible light. The absorption spectrum describes its photo sensitivity in the range of wavelength from 200 nm to 850 nm. Simulation of current-intensity of light curve is carried out and experimental results are found in good agreement with simulated ones.

Copper phthalocyanine and metal free phthalocyanine bulk heterojunction photodetector

International Nuclear Information System (INIS)

Farooq, Amjad; Karimov, Kh.S.; Ahmed, Nisar; Ali, Taimoor; Khalid Alamgir, M.; Usman, Muhammad

2015-01-01

In this study we present the dependence of electrical properties of copper phthalocyanine (CuPc) and metal free phthalocyanine (H 2 Pc) bulk heterojunction structure under different illumination levels. To fabricate the device on ITO coated glass substrate the bulk heterojunction thin film of CuPc and H 2 Pc with thickness varying from 100 nm to 300 nm are deposited by thermal evaporator. Aluminum thin film was deposited by thermal evaporation as a top contact. The optical properties of the fabricated device are investigated using UV–vis spectroscopy. The current-voltage characteristics in dark and under illumination show that the device is sensitive towards visible light. The absorption spectrum describes its photo sensitivity in the range of wavelength from 200 nm to 850 nm. Simulation of current-intensity of light curve is carried out and experimental results are found in good agreement with simulated ones

Delignified and Densified Cellulose Bulk Materials with Excellent Tensile Properties for Sustainable Engineering.

Science.gov (United States)

Frey, Marion; Widner, Daniel; Segmehl, Jana S; Casdorff, Kirstin; Keplinger, Tobias; Burgert, Ingo

2018-02-07

Today's materials research aims at excellent mechanical performance in combination with advanced functionality. In this regard, great progress has been made in tailoring the materials by assembly processes in bottom-up approaches. In the field of wood-derived materials, nanocellulose research has gained increasing attention, and materials with advanced properties were developed. However, there are still unresolved issues concerning upscaling for large-scale applications. Alternatively, the sophisticated hierarchical scaffold of wood can be utilized in a top-down approach to upscale functionalization, and one can profit at the same time from its renewable nature, CO 2 storing capacity, light weight, and good mechanical performance. Nevertheless, for bulk wood materials, a wider multipurpose industrial use is so far impeded by concerns regarding durability, natural heterogeneity as well as limitations in terms of functionalization, processing, and shaping. Here, we present a novel cellulose bulk material concept based on delignification and densification of wood resulting in a high-performance material. A delignification process using hydrogen peroxide and acetic acid was optimized to delignify the entire bulk wooden blocks and to retain the highly beneficial structural directionality of wood. In a subsequent step, these cellulosic blocks were densified in a process combining compression and lateral shear to gain a very compact cellulosic material with entangled fibers while retaining unidirectional fiber orientation. The cellulose bulk materials obtained by different densification protocols were structurally, chemically, and mechanically characterized revealing superior tensile properties compared to native wood. Furthermore, after delignification, the cellulose bulk material can be easily formed into different shapes, and the delignification facilitates functionalization of the bioscaffold.

Optical properties of bulk semiconductors and graphene/boron nitride: the Bethe-Salpeter equation with derivative discontinuity-corrected density functional energies

DEFF Research Database (Denmark)

Yan, Jun; Jacobsen, Karsten W.; Thygesen, Kristian S.

2012-01-01

-dimensional systems of graphene and hexagonal boron-nitride (h-BN) we find good agreement with previous many-body calculations. For the graphene/h-BN interface we find that the fundamental and optical gaps of the h-BN layer are reduced by 2.0 and 0.7 eV, respectively, compared to freestanding h-BN. This reduction......We present an efficient implementation of the Bethe-Salpeter equation (BSE) for optical properties of materials in the projector augmented wave method Grid-based projector-augmented wave method (GPAW). Single-particle energies and wave functions are obtained from the Gritsenko, Leeuwen, Lenthe...

Optical properties of non-spherical desert dust particles in the terrestrial infrared – An asymptotic approximation approach

International Nuclear Information System (INIS)

Klüser, Lars; Di Biagio, Claudia; Kleiber, Paul D.; Formenti, Paola; Grassian, Vicki H.

2016-01-01

Optical properties (extinction efficiency, single scattering albedo, asymmetry parameter and scattering phase function) of five different desert dust minerals have been calculated with an asymptotic approximation approach (AAA) for non-spherical particles. The AAA method combines Rayleigh-limit approximations with an asymptotic geometric optics solution in a simple and straightforward formulation. The simulated extinction spectra have been compared with classical Lorenz–Mie calculations as well as with laboratory measurements of dust extinction. This comparison has been done for single minerals and with bulk dust samples collected from desert environments. It is shown that the non-spherical asymptotic approximation improves the spectral extinction pattern, including position of the extinction peaks, compared to the Lorenz–Mie calculations for spherical particles. Squared correlation coefficients from the asymptotic approach range from 0.84 to 0.96 for the mineral components whereas the corresponding numbers for Lorenz–Mie simulations range from 0.54 to 0.85. Moreover the blue shift typically found in Lorenz–Mie results is not present in the AAA simulations. The comparison of spectra simulated with the AAA for different shape assumptions suggests that the differences mainly stem from the assumption of the particle shape and not from the formulation of the method itself. It has been shown that the choice of particle shape strongly impacts the quality of the simulations. Additionally, the comparison of simulated extinction spectra with bulk dust measurements indicates that within airborne dust the composition may be inhomogeneous over the range of dust particle sizes, making the calculation of reliable radiative properties of desert dust even more complex. - Highlights: • A fast and simple method for estimating optical properties of dust. • Can be used with non-spherical particles of arbitrary size distributions. • Comparison with Mie simulations and

Thermal and optical properties of porous silicon

Directory of Open Access Journals (Sweden)

Silva A. Ferreira da

2001-01-01

Full Text Available Thermal diffusivity and optical absorption have been investigated for porous silicon, at room temperature, using photoacoustic spectroscopy. The experimental results obtained conform well with the existing studies recently published. The value obtained for thermal diffusivity is 0.045 ± 0.002 cm²/s.The absorption onsets show energy structures, differing from the ordinary semiconductor of bulk type.

Electronic and Optical Properties of Twisted Bilayer Graphene

Science.gov (United States)

Huang, Shengqiang

The ability to isolate single atomic layers of van der Waals materials has led to renewed interest in the electronic and optical properties of these materials as they can be fundamentally different at the monolayer limit. Moreover, these 2D crystals can be assembled together layer by layer, with controllable sequence and orientation, to form artificial materials that exhibit new features that are not found in monolayers nor bulk. Twisted bilayer graphene is one such prototype system formed by two monolayer graphene layers placed on top of each other with a twist angle between their lattices, whose electronic band structure depends on the twist angle. This thesis presents the efforts to explore the electronic and optical properties of twisted bilayer graphene by Raman spectroscopy and scanning tunneling microscopy measurements. We first synthesize twisted bilayer graphene with various twist angles via chemical vapor deposition. Using a combination of scanning tunneling microscopy and Raman spectroscopy, the twist angles are determined. The strength of the Raman G peak is sensitive to the electronic band structure of twisted bilayer graphene and therefore we use this peak to monitor changes upon doping. Our results demonstrate the ability to modify the electronic and optical properties of twisted bilayer graphene with doping. We also fabricate twisted bilayer graphene by controllable stacking of two graphene monolayers with a dry transfer technique. For twist angles smaller than one degree, many body interactions play an important role. It requires eight electrons per moire unit cell to fill up each band instead of four electrons in the case of a larger twist angle. For twist angles smaller than 0.4 degree, a network of domain walls separating AB and BA stacking regions forms, which are predicted to host topologically protected helical states. Using scanning tunneling microscopy and spectroscopy, these states are confirmed to appear on the domain walls when inversion

Optical conductivity of topological insulator thin films

International Nuclear Information System (INIS)

Li, L. L.; Xu, W.; Peeters, F. M.

2015-01-01

We present a detailed theoretical study on the optoelectronic properties of topological insulator thin film (TITFs). The k·p approach is employed to calculate the energy spectra and wave functions for both the bulk and surface states in the TITF. With these obtained results, the optical conductivities induced by different electronic transitions among the bulk and surface states are evaluated using the energy-balance equation derived from the Boltzmann equation. We find that for Bi 2 Se 3 -based TITFs, three characteristic regimes for the optical absorption can be observed. (i) In the low radiation frequency regime (photon energy ℏω<200 meV), the free-carrier absorption takes place due to intraband electronic transitions. An optical absorption window can be observed. (ii) In the intermediate radiation frequency regime (200<ℏω<300 meV), the optical absorption is induced mainly by interband electronic transitions from surface states in the valance band to surface states in the conduction band and an universal value σ 0 =e 2 /(8ℏ) for the optical conductivity can be obtained. (iii) In the high radiation frequency regime (ℏω>300 meV), the optical absorption can be achieved via interband electronic transitions from bulk and surface states in the valance band to bulk and surface states in the conduction band. A strong absorption peak can be observed. These interesting findings indicate that optical measurements can be applied to identify the energy regimes of bulk and surface states in the TITF

Defined wetting properties of optical surfaces

Science.gov (United States)

Felde, Nadja; Coriand, Luisa; Schröder, Sven; Duparré, Angela; Tünnermann, Andreas

2017-10-01

Optical surfaces equipped with specific functional properties have attracted increasing importance over the last decades. In the light of cost reduction, hydrophobic self-cleaning behavior is aspired. On the other side, hydrophilic properties are interesting due to their anti-fog effect. It has become well known that such wetting states are significantly affected by the surface morphology. For optical surfaces, however, this fact poses a problem, as surface roughness can induce light scattering. The generation of optical surfaces with specific wetting properties, hence, requires a profound understanding of the relation between the wetting and the structural surface properties. Thus, our work concentrates on a reliable acquisition of roughness data over a wide spatial frequency range as well as on the comprehensive description of the wetting states, which is needed for the establishment of such correlations. We will present our advanced wetting analysis for nanorough optical surfaces, extended by a vibration-based procedure, which is mainly for understanding and tailoring the wetting behavior of various solid-liquid systems in research and industry. Utilizing the relationships between surface roughness and wetting, it will be demonstrated how different wetting states for hydrophobicity and hydrophilicity can be realized on optical surfaces with minimized scatter losses.

Performance Comparison between Optical Fiber Type ESPI and Bulk Type ESPI for the Internal Defect in Pressure Vessel

International Nuclear Information System (INIS)

Kim, Seong Jong; Kang, Young June; Hong, Kyung Min; Lee, Jae Hoon; Choi, Nak Jung

2012-01-01

An optical defect detection method using ESPI(electronic speckle pattern interferometry) is proposed. ESPI is widely used as a non-contact measurement system which show deformation and phase map in real time. ESPI can be divided as the in-plane, out-of-plane and shearography by operation principle and target object and also divided with bulk type and optic fiber type by the optic configurations. This paper is focused on optic fiber type out-of-plane ESPI, which has the following advantages: (1) low cost: (2) reduction of the unreliable factors generated by separated optic components: (3) simplification of the optic configuration: (4) great reduction of volume: (5) flexibility, to be easily designed into different structures to adapt to inaccessible environments such as pipeline cavity and so on

Mechanical properties of Nd-Ba-Cu-O bulk superconductors

International Nuclear Information System (INIS)

Matsui, Motohide; Sakai, Naomichi; Murakami, Masato; Osamura, Kozo

2003-01-01

We investigated the effects of Nd422 and Ag particles on the mechanical properties in Nd-Ba-Cu-O bulk superconductors. Both Nd422 and Ag particles were effective in decreasing the amount of microcracks running along the c direction. In the case of Nd422, however, excessive Nd422 addition enhanced the crack propagation, resulting in the degradation of mechanical strength. In the case of Ag addition, the beneficial effect of its ductile mechanical property was not observed. This was due to a relatively large size of Ag particles and low interfacial strength between Ag and Nd123 matrix. It was remarkable that the Weibull coefficient of the sample with Ag 2 O addition exceeded 13, which is reliable enough for practical engineering applications

Silver metaphosphate glass wires inside silica fibers--a new approach for hybrid optical fibers.

Science.gov (United States)

Jain, Chhavi; Rodrigues, Bruno P; Wieduwilt, Torsten; Kobelke, Jens; Wondraczek, Lothar; Schmidt, Markus A

2016-02-22

Phosphate glasses represent promising candidates for next-generation photonic devices due to their unique characteristics, such as vastly tunable optical properties, and high rare earth solubility. Here we show that silver metaphosphate wires with bulk optical properties and diameters as small as 2 µm can be integrated into silica fibers using pressure-assisted melt filling. By analyzing two types of hybrid metaphosphate-silica fibers, we show that the filled metaphosphate glass has only negligible higher attenuation and a refractive index that is identical to the bulk material. The presented results pave the way towards new fiber-type optical devices relying on metaphosphate glasses, which are promising materials for applications in nonlinear optics, sensing and spectral filtering.

Microstructure and tensile properties of bulk nanostructured aluminum/graphene composites prepared via cryomilling

Energy Technology Data Exchange (ETDEWEB)

Li, J.L., E-mail: ljlhpu123@163.com; Xiong, Y.C.; Wang, X.D.; Yan, S.J.; Yang, C.; He, W.W.; Chen, J.Z.; Wang, S.Q.; Zhang, X.Y.; Dai, S.L.

2015-02-25

In order to develop high strength metal–matrix composites with acceptable ductility, bulk nanostructured aluminum–matrix composites reinforced with graphene nanoflakes were fabricated by cryomilling and hot extrusion processes. Microstructure and mechanical properties were characterized and determined using transmission electron microscopy, electron dispersion spectroscopy, as well as static tensile tests. The results show that, with an addition of only 0.5 wt% graphene nanoflakes, the bulk nanostructured aluminum/graphene composite exhibited increased strength and unsubdued ductility over pure aluminum. Besides, the mechanical properties of the composites with higher content of graphene nanoflakes were also measured and investigated. Above 1.0 wt% of graphene nanoflakes, however, this strengthening effect sharply dropped due to the clustering of graphene nanoflakes. Furthermore, the optimal addition of graphene nanoflakes into the nanocrystalline aluminum matrix was calculated and discussed.

Structure and property evaluation of a vacuum plasma sprayed nanostructured tungsten-hafnium carbide bulk composite

International Nuclear Information System (INIS)

Rea, K.E.; Viswanathan, V.; Kruize, A.; Hosson, J.Th.M. de; O'Dell, S.; McKechnie, T.; Rajagopalan, S.; Vaidyanathan, R.; Seal, S.

2008-01-01

Vacuum plasma spray (VPS) forming of tungsten-based metal matrix nanocomposites (MMCs) has shown to be a cost effective and time saving method for the formation of bulk monolithic nanostructured thermo-mechanical components. Spray drying of powder feedstock appears to have a significant effect on the improved mechanical properties of the bulk nanocomposite. The reported elastic modulus of the nanocomposite nearly doubles due to the presence of HfC nano particulates in the W matrix. High resolution transmission electron microscopy (HRTEM) revealed the retention of nanostructures at the select process conditions and is correlated with the enhanced mechanical properties of the nanocomposite

Optical Properties of Rotationally Twinned Nanowire Superlattices

DEFF Research Database (Denmark)

Bao, Jiming; Bell, David C.; Capasso, Federico

2008-01-01

We have developed a technique so that both transmission electron microscopy and microphotoluminescence can be performed on the same semiconductor nanowire over a large range of optical power, thus allowing us to directly correlate structural and optical properties of rotationally twinned zinc...... a heterostructure in a chemically homogeneous nanowire material and alter in a major way its optical properties opens new possibilities for band-structure engineering....

Chemical, electronic, and magnetic structure of LaFeCoSi alloy: Surface and bulk properties

Energy Technology Data Exchange (ETDEWEB)

Lollobrigida, V. [Dipartimento di Scienze, Università Roma Tre, I-00146 Rome (Italy); Dipartimento di Matematica e Fisica, Università Roma Tre, I-00146 Rome (Italy); Basso, V.; Kuepferling, M.; Coïsson, M.; Olivetti, E. S.; Celegato, F. [Istituto Nazionale di Ricerca Metrologica (INRIM), I-10135 Torino (Italy); Borgatti, F. [CNR, Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), I-40129 Bologna (Italy); Torelli, P.; Panaccione, G. [CNR, Istituto Officina dei Materiali (IOM), Lab. TASC, I-34149 Trieste (Italy); Tortora, L. [Laboratorio di Analisi di Superficie, Dipartimento di Matematica e Fisica, Università Roma Tre, I-00146 Rome (Italy); Dipartimento di Ingegneria Meccanica, Università Tor Vergata, I-00133 Rome (Italy); Stefani, G.; Offi, F. [Dipartimento di Scienze, Università Roma Tre, I-00146 Rome (Italy)

2014-05-28

We investigate the chemical, electronic, and magnetic structure of the magnetocaloric LaFeCoSi compound with bulk and surface sensitive techniques. We put in evidence that the surface retains a soft ferromagnetic behavior at temperatures higher than the Curie temperature of the bulk due to the presence of Fe clusters at the surface only. This peculiar magnetic surface effect is attributed to the exchange interaction between the ferromagnetic Fe clusters located at the surface and the bulk magnetocaloric alloy, and it is used here to monitor the magnetic properties of the alloy itself.

Chemical, electronic, and magnetic structure of LaFeCoSi alloy: Surface and bulk properties

Science.gov (United States)

Lollobrigida, V.; Basso, V.; Borgatti, F.; Torelli, P.; Kuepferling, M.; Coïsson, M.; Olivetti, E. S.; Celegato, F.; Tortora, L.; Stefani, G.; Panaccione, G.; Offi, F.

2014-05-01

We investigate the chemical, electronic, and magnetic structure of the magnetocaloric LaFeCoSi compound with bulk and surface sensitive techniques. We put in evidence that the surface retains a soft ferromagnetic behavior at temperatures higher than the Curie temperature of the bulk due to the presence of Fe clusters at the surface only. This peculiar magnetic surface effect is attributed to the exchange interaction between the ferromagnetic Fe clusters located at the surface and the bulk magnetocaloric alloy, and it is used here to monitor the magnetic properties of the alloy itself.

Chemical, electronic, and magnetic structure of LaFeCoSi alloy: Surface and bulk properties

International Nuclear Information System (INIS)

Lollobrigida, V.; Basso, V.; Kuepferling, M.; Coïsson, M.; Olivetti, E. S.; Celegato, F.; Borgatti, F.; Torelli, P.; Panaccione, G.; Tortora, L.; Stefani, G.; Offi, F.

2014-01-01

We investigate the chemical, electronic, and magnetic structure of the magnetocaloric LaFeCoSi compound with bulk and surface sensitive techniques. We put in evidence that the surface retains a soft ferromagnetic behavior at temperatures higher than the Curie temperature of the bulk due to the presence of Fe clusters at the surface only. This peculiar magnetic surface effect is attributed to the exchange interaction between the ferromagnetic Fe clusters located at the surface and the bulk magnetocaloric alloy, and it is used here to monitor the magnetic properties of the alloy itself.

Formation of SiN{sub x}:H by PECVD: optimization of the optical, bulk passivation and structural properties for photovoltaic applications; Elaboration de SiN{sub x}:H par PECVD: optimisation des proprietes optiques, passivantes et structurales pour applications photovoltaiques

Energy Technology Data Exchange (ETDEWEB)

Lelievre, J.F

2007-04-15

The hydrogenated silicon nitride SiNx:H is widely used as antireflection coating and passivation layer in the manufacture of silicon photovoltaic cells. The aim of this work was to implement a low frequency (440 kHz) PECVD reactor and to characterize the obtained SiN layers. After having determined the parameters of the optimal deposition, the physico-chemical structure of the layers has been studied. The optical properties have been studied with the aim to improve the antireflection coating of the photovoltaic cells. The surface and bulk passivation properties, induced by the SiN layer in terms of its stoichiometry, have been analyzed and have revealed the excellent passivating efficiency of this material. At last, have been studied the formation conditions of the silicon nano-crystals in the SiN matrix. (O.M.)

Effect of oxidative enzymes on bulk rheological properties of wheat flour doughs

NARCIS (Netherlands)

Dunnewind, B.; Vliet, T. van; Orsel, R.

2002-01-01

The use of enzymes such as peroxidases or glucose oxidase instead of chemical oxidants is a very interesting option for improving breadmaking performance of doughs. In this study the effect of such enzymes on bulk rheological properties of dough was quantified and their influence on the polymer

Effect of Oxidative Enzymes on Bulk Rheological Properties of Wheat Flour Doughs

NARCIS (Netherlands)

Dunnewind, B.; Vliet, van T.; Orsel, R.

2002-01-01

The use of enzymes such as peroxidases or glucose oxidase instead of chemical oxidants is a very interesting option for improving breadmaking performance of doughs. In this study the effect of such enzymes on bulk rheological properties of dough was quantified and their influence on the polymer

Pion condensation in a theory consistent with bulk properties of nuclear matter

International Nuclear Information System (INIS)

Glendenning, N.K.

1980-01-01

A relativistic field theory of nuclear matter is solved for the self-consistent field strengths inthe mean-field approximation. The theory is constrained to reproduce the bulk properties of nuclear matter. A weak pion condensate is compatible with this constraint. At least this is encouraging as concerns the possible existence of a new phase of nuclear matter. In contrast, the Lee-Wick density isomer is probably not compatible with the properties of nuclear matter. 3 figures

Optical properties of graphene superlattices.

Science.gov (United States)

Le, H Anh; Ho, S Ta; Nguyen, D Chien; Do, V Nam

2014-10-08

In this work, the optical responses of graphene superlattices, i.e. graphene subjected to a periodic scalar potential, are theoretically reported. The optical properties were studied by investigating the optical conductivity, which was calculated using the Kubo formalism. It was found that the optical conductivity becomes dependent on the photon polarization and is suppressed in the photon energy range of (0, Ub), where Ub is the potential barrier height. In the higher photon energy range, i.e. Ω > Ub, the optical conductivity is, however, almost identical to that of pristine graphene. Such behaviors of the optical conductivity are explained microscopically through the analysis of the elements of optical matrices and effectively through a simple model, which is based on the Pauli blocking mechanism.

Ab-initio study of the magneto-optical properties of the ultrathin films of Fe{sub n}/Au(001)

Energy Technology Data Exchange (ETDEWEB)

Boukelkoul, Mebarek, E-mail: boukelkoul_mebarek@yahoo.fr [Laboratoire de Physique Quantique et Systèmes Dynamiques, Faculté des sciences, Université Sétif1, Sétif, 19000 Algeria (Algeria); Haroun, Mohamed Fahim [Laboratoire de Physique Quantique et Systèmes Dynamiques, Faculté des sciences, Université Sétif1, Sétif, 19000 Algeria (Algeria); Haroun, Abdelhalim [Laboratoire de Physique Quantique et Systèmes Dynamiques, Faculté des sciences, Université Sétif1, Sétif, 19000 Algeria (Algeria); IPCMS, UMR 7504 CNRS-UNISTRA, 23 Rue du Loess, Strasbourg, 67034 France (France)

2016-12-15

With the aim of understand the microscopic origin of the magneto-optical response in the Fe ultrathin films, we used the first principle full-relativistic Spin-Polarized Relativistic Linear Muffin-Tin Orbitals with Atomic Sphere Approximation. We performed an ab-initio study of the structural, magnetic and magneto-optical properties of Fe deposited on semi-infinite Au(001). The structure and growth of the film leads to a pseudomorphic body centered tetragonal structure with tetragonality ratio c/a=1.62, and the pseudomorphic growth is found to be larger than 3 monolayers. The magnetic study revealed a ferromagnetic phase with a large magnetic moment compared to the bulk one. The magneto-optical response is calculated via the polar magneto-optical Kerr effect over a photon energy range up to 10 eV. The most important features of the Kerr rotation spectra are interpreted trough the interband transitions between localized states.

Laser-induced damage thresholds of bulk and coating optical materials at 1030  nm, 500  fs.

Science.gov (United States)

Gallais, Laurent; Commandré, Mireille

2014-02-01

We report on extensive femtosecond laser damage threshold measurements of optical materials in both bulk and thin-film form. This study, which is based on published and new data, involved simple oxide and fluoride films, composite films made from a mixture of two dielectric materials, metallic films, and the surfaces of various bulk materials: oxides, fluorides, semiconductors, and ionic crystals. The samples were tested in comparable conditions at 1030 nm, 375 to 600 fs, under single-pulse irradiation. A large number of different samples prepared by different deposition techniques have been tested, involving classical materials used in the fabrication of optical thin film components (Ag, AlF3, Al2O3, HfO2, MgF2, Nb2O5, Pt, Sc2O3, SiO2, Ta2O5, Y2O3, and ZrO2) and their combination with codeposition processes. Their behaviors are compared with the surfaces of bulk materials (Al2O3, BaF2, CaF2, Ge, KBr, LiF, MgF2, NaCl, Quartz, Si, ZnS, ZnSe, and different silica glasses). Tabulated values of results are presented and discussed.

Electronic and structural properties of TiB2: Bulk, surface, and nanoscale effects

International Nuclear Information System (INIS)

Volonakis, George; Tsetseris, Leonidas; Logothetidis, Stergios

2011-01-01

Titanium diboride (TiB 2 ), is a widely used hard material that comprises graphene-like layers of B and intercalated Ti atoms. Here we report the results of extensive first-principles calculations on key properties of bulk TiB 2 , TiB 2 surfaces, and TiB 2 nanocrystals (NCs). The computational approach is first validated based on the agreement between calculated structural and electronic properties of bulk TiB 2 and available experimental and theoretical data. We then obtain the formation energies for several surface cuts and use these values to construct TiB 2 NCs based on the Wulff theorem. Finally, we demonstrate by studying the adsorption of small molecules that hydrogen and oxygen adatoms can be attached through strongly exothermic chemisorption reactions on TiB 2 surfaces. Likewise, water molecules bind on various TiB 2 surfaces and NC facets, with an energetic preference for the latter. The results are relevant to applications that depend on reactivity-related TiB 2 properties, for example resistance to corrosion and interactions with water-based solutions.

Formation and properties of two-phase bulk metallic glasses by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Xie Guoqiang, E-mail: xiegq@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Louzguine-Luzgin, D.V. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Inoue, Akihisa [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

2011-06-15

Research highlights: > Two-phase bulk metallic glasses with high strength and good soft magnetic properties as well as satisfying large-size requirements were produced by spark plasma sintering. > Effects of sintering temperature on thermal stability, microstructure, mechanical and magnetic properties were investigated. > Densified samples were obtained by the spark plasma sintering at above 773 K. - Abstract: Using a mixture of the gas-atomized Ni{sub 52.5}Nb{sub 10}Zr{sub 15}Ti{sub 15}Pt{sub 7.5} and Fe{sub 73}Si{sub 7}B{sub 17}Nb{sub 3} glassy alloy powders, we produced the two-phase bulk metallic glass (BMG) with high strength and good soft magnetic properties as well as satisfying large-size requirements by the spark plasma sintering (SPS) process. Two kinds of glassy particulates were homogeneously dispersed each other. With an increase in sintering temperature, density of the produced samples increased, and densified samples were obtained by the SPS process at above 773 K. Good bonding state among the Ni- and Fe-based glassy particulates was achieved.

Correlations between elastic moduli and properties in bulk metallic glasses

International Nuclear Information System (INIS)

Wang Weihua

2006-01-01

A survey of the elastic, mechanical, fragility, and thermodynamic properties of bulk metallic glasses (BMGs) and glass-forming liquids is presented. It is found that the elastic moduli of BMGs have correlations with the glass transition temperature, melting temperature, mechanical properties, and even liquid fragility. On the other hand, the elastic constants of available BMGs show a rough correlation with a weighted average of the elastic constants for the constituent elements. Although the theoretical and physical reasons for the correlations are to be clarified, these correlations could assist in understanding the long-standing issues of glass formation and the nature of glass and simulate the work of theorists. Based on the correlation, we show that the elastic moduli can assist in selecting alloying components for controlling the elastic properties and glass-forming ability of the BMGs and thus can guide BMG design. As case study, we report the formation of the families of rare-earth-based BMGs with controllable properties

Measuring optical properties of a blood vessel model using optical coherence tomography

Science.gov (United States)

Levitz, David; Hinds, Monica T.; Tran, Noi; Vartanian, Keri; Hanson, Stephen R.; Jacques, Steven L.

2006-02-01

In this paper we develop the concept of a tissue-engineered optical phantom that uses engineered tissue as a phantom for calibration and optimization of biomedical optics instrumentation. With this method, the effects of biological processes on measured signals can be studied in a well controlled manner. To demonstrate this concept, we attempted to investigate how the cellular remodeling of a collagen matrix affected the optical properties extracted from optical coherence tomography (OCT) images of the samples. Tissue-engineered optical phantoms of the vascular system were created by seeding smooth muscle cells in a collagen matrix. Four different optical properties were evaluated by fitting the OCT signal to 2 different models: the sample reflectivity ρ and attenuation parameter μ were extracted from the single scattering model, and the scattering coefficient μ s and root-mean-square scattering angle θ rms were extracted from the extended Huygens-Fresnel model. We found that while contraction of the smooth muscle cells was clearly evident macroscopically, on the microscopic scale very few cells were actually embedded in the collagen. Consequently, no significant difference between the cellular and acellular samples in either set of measured optical properties was observed. We believe that further optimization of our tissue-engineering methods is needed in order to make the histology and biochemistry of the cellular samples sufficiently different from the acellular samples on the microscopic level. Once these methods are optimized, we can better verify whether the optical properties of the cellular and acellular collagen samples differ.

First-principles study of structural, electronic, linear and nonlinear optical properties of Ga{2}PSb ternary chalcopyrite

Science.gov (United States)

Ouahrani, T.; Reshak, A. H.; de La Roza, A. Otero; Mebrouki, M.; Luaña, V.; Khenata, R.; Amrani, B.

2009-12-01

We report results from first-principles density functional calculations using the full-potential linear augmented plane wave (FP-LAPW) method. The generalized gradient approximation (GGA) and the Engel-Vosko-generalized gradient approximation (EV-GGA) were used for the exchange-correlation energy of the structural, electronic, linear and nonlinear optical properties of the chalcopyrite Ga2PSb compound. The valence band maximum (VBM) is located at the Γv point, and the conduction band minimum (CBM) is located at the Γc point, resulting in a direct band gap of about 0.365 eV for GGA and 0.83 eV for EV-GGA. In comparison with the experimental one (1.2 eV) we found that EV-GGA calculation gives energy gap in reasonable agreement with the experiment. The spin orbit coupling has marginal influence on the optical properties. The ground state quantities such as lattice parameters (a, c and u), bulk modules B and its pressure derivative B^primeare evaluated.

Optical properties of graphene superlattices

International Nuclear Information System (INIS)

Le, H Anh; Do, V Nam; Ho, S Ta; Nguyen, D Chien

2014-01-01

In this work, the optical responses of graphene superlattices, i.e. graphene subjected to a periodic scalar potential, are theoretically reported. The optical properties were studied by investigating the optical conductivity, which was calculated using the Kubo formalism. It was found that the optical conductivity becomes dependent on the photon polarization and is suppressed in the photon energy range of (0, U b ), where U b is the potential barrier height. In the higher photon energy range, i.e. Ω > U b , the optical conductivity is, however, almost identical to that of pristine graphene. Such behaviors of the optical conductivity are explained microscopically through the analysis of the elements of optical matrices and effectively through a simple model, which is based on the Pauli blocking mechanism. (paper)

First principle electronic, structural, elastic, and optical properties of strontium titanate

Directory of Open Access Journals (Sweden)

Chinedu E. Ekuma

2012-03-01

Full Text Available We report self-consistent ab-initio electronic, structural, elastic, and optical properties of cubic SrTiO3 perovskite. Our non-relativistic calculations employed a generalized gradient approximation (GGA potential and the linear combination of atomic orbitals (LCAO formalism. The distinctive feature of our computations stem from solving self-consistently the system of equations describing the GGA, using the Bagayoko-Zhao-Williams (BZW method. Our results are in agreement with experimental ones where the later are available. In particular, our theoretical, indirect band gap of 3.24 eV, at the experimental lattice constant of 3.91 Å, is in excellent agreement with experiment. Our predicted, equilibrium lattice constant is 3.92 Å, with a corresponding indirect band gap of 3.21 eV and bulk modulus of 183 GPa.

Structural, electrical, and optical properties of polycrystalline NbO_2 thin films grown on glass substrates by solid phase crystallization

International Nuclear Information System (INIS)

Nakao, Shoichiro; Kamisaka, Hideyuki; Hirose, Yasushi; Hasegawa, Tetsuya

2017-01-01

We investigated the structural, electrical, and optical properties of polycrystalline NbO_2 thin films on glass substrates. The NbO_2 films were crystallized from amorphous precursor films grown by pulsed laser deposition at various oxygen partial pressures (P_O_2). The electrical and optical properties of the precursor films systematically changed with P_O_2, demonstrating that the oxygen content of the precursor films can be finely controlled with P_O_2. The precursors were crystallized into polycrystalline NbO_2 films by annealing under vacuum at 600 C. The NbO_2 films possessed extremely flat surfaces with branching patterns. Even optimized films showed a low resistivity (ρ) of 2 x 10"2 Ω cm, which is much lower than the bulk value of 1 x 10"4 Ω cm, probably because of the inferior crystallinity of the films compared with that of a bulk NbO_2 crystal. Both oxygen-rich and -poor NbO_2 films showed lower ρ than that of the stoichiometric film. The NbO_2 film with the highest ρ showed an indirect bandgap of 0.7 eV. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Comparing optical properties of different species of diatoms

DEFF Research Database (Denmark)

Maibohm, Christian; Friis, Søren Michael Mørk; Su, Y.

2015-01-01

species dependent with huge variety in size, shape, and micro- structure. We have experimentally investigated optical properties of frustules of several species of diatoms to further understand light harvesting properties together with commo n traits, effects and differences between the different...... analysis software. The software uses parameters which are extracted from experimental im ages as basis for simulation and allows us to extract the influence of the different elements of the frustule. The information could be used both for predicting optical properties of diatoms and by changing frustule...... parameters, maybe by altering growth conditions of the diatoms tailor their optical properties....

The magneto-optical properties of non-uniform graphene nanoribbons

Science.gov (United States)

Chung, Hsien-Ching; Lin, Ming-Fa

2015-03-01

When synthesizing few-layer graphene nanoribbons (GNRs), non-uniform GNRs would be made simultaneously. Recently, the non-uniform GNRs, which is a stack of two GNRs with unequal widths, have been fabricated by mechanically exfoliated from bulk graphite. Some theoretical predictions have been reported, such as gap opening and transport properties. Under the influence of magnetic fields, magnetic quantization takes place and drastically changes the electronic properties. By tuning the geometric configuration, four categories of magneto-electronic spectra are exhibited. (1) The spectrum is mostly contributed by quasi-Landau levels (QLLs) of monolayer GNRs. (2) The spectrum displays two groups of QLLs, and the non-uniform GNR behaves like a bilayer one. (3) An intermediate category, the spectrum is composite disordered. (4) The spectrum presents the coexistence of monolayer and bilayer spectra. In this work, the magneto-electronic and optical properties for different geometric configurations are given, such as energy dispersions, density of states, wave functions, and magneto-absorption spectra are presented. Furthermore, the transformation between monolayer and bilayer spectra as well as the coexistence of monolayer and bilayer spectra are discussed in detail. One of us (Hsien-Ching Chung) thanks Ming-Hui Chung and Su-Ming Chen for financial support. This work was supported in part by the National Science Council of Taiwan under Grant Number 98-2112-M-006-013-MY4.

Doping in silicon nanocrystals: An ab initio study of the structural, electronic and optical properties

International Nuclear Information System (INIS)

Iori, Federico; Degoli, Elena; Luppi, Eleonora; Magri, Rita; Marri, Ivan; Cantele, G.; Ninno, D.; Trani, F.; Ossicini, Stefano

2006-01-01

There are experimental evidences that doping control at the nanoscale can significantly modify the optical properties with respect to the pure systems. This is the case of silicon nanocrystals (Si-nc), for which it has been shown that the photoluminescence (PL) peak can be tuned also below the bulk Si band gap by properly controlling the impurities, for example by boron (B) and phosphorus (P) codoping. In this work, we report on an ab initio study of impurity states in Si-nc. We consider B and P substitutional impurities for Si-nc with a diameter up to 2.2 nm. Formation energies (FEs), electronic, optical and structural properties have been determined as a function of the cluster dimension. For both B-doped and P-doped Si-nc the FE increases on decreasing the dimension, showing that the substitutional doping gets progressively more difficult for the smaller nanocrystals. Moreover, subsurface impurity positions result to be the most stable ones. The codoping reduces the FE strongly favoring this process with respect to the simple n-doping or p-doping. Such an effect can be attributed to charge compensation between the donor and the acceptor atoms. Moreover, smaller structural deformations, with respect to n-doped and p-doped cases, localized only around the impurity sites are observed. The band gap and the optical threshold are largely reduced with respect to the undoped Si-nc showing the possibility of an impurity-based engineering of the Si-nc PL properties

Optical limiting properties of optically active phthalocyanine derivatives

Science.gov (United States)

Wang, Peng; Zhang, Shuang; Wu, Peiji; Ye, Cheng; Liu, Hongwei; Xi, Fu

2001-06-01

The optical limiting properties of four optically active phthalocyanine derivatives in chloroform solutions and epoxy resin thin plates were measured at 532 nm with 10 ns pulses. The excited state absorption cross-section σex and refractive-index cross-section σr were determined with the Z-scan technique. These chromophores possess larger σex than the ground state absorption cross-section σ0, indicating that they are the potential materials for reverse saturable absorption (RSA). The negative σr values of these chromophores add to the thermal contribution, producing a larger defocusing effect, which may be helpful in further enhancing their optical limiting performance. The optical limiting responses of the thin plate samples are stronger than those of the chloroform solutions.

The phase transition and elastic and optical properties of polymorphs of CuI

International Nuclear Information System (INIS)

Zhu Jiajie; Pandey, Ravindra; Gu Mu

2012-01-01

The high-pressure polymorphs of CuI have attracted much attention due to the somewhat contradictory identification of their structures by means of x-ray diffraction measurements and theoretical calculations. In this paper, we report the results of a theoretical investigation of polymorphs of CuI including zinc-blende, rhombohedral, tetragonal, rocksalt and orthorhombic phases. We find that CuI follows the high-pressure transition path from the zinc-blende phase to the orthorhombic phase via the tetragonal phase, and the rhombohedral phase shows mechanical instability under high pressure. The bulk moduli are almost isotropic but the shear moduli show large anisotropy in these polymorphs. A relatively strong hybridization of I p and Cu d states appears to determine the electronic properties of the CuI polymorphs. The zinc-blende and tetragonal CuI are direct gap semiconductors and their optical properties are similar, whereas the orthorhombic CuI is metallic.

Exploitation of inimitable properties of CuInS2 quantum dots for energy conversion in bulk heterojunction hybrid solar cell

Science.gov (United States)

Jindal, Shikha; Giripunje, Sushama M.

2017-11-01

Quantum dots (QDs) are the suitable material for solar cell devices owing to its distinctive optical, electrical and electronic properties. Currently, the most efficient devices have employed the toxic QDs which cause destructive impact on environment. In the present article, we have used environment benign CuInS2 QDs as an acceptor material in bulk heterojunction device of P3HT and QDs. The energy level positions corroborated from UPS spectra substantiates the acceptor property of CuInS2. We scrutinized the hybrid solar cell by tailoring the acceptor content in active layer. The increased acceptor content intensifies the performance of device. The enhancement in photovoltaic parameters is mainly due to the fast dissociation and extraction of photogenerated excitons which occurs with the larger wt% of acceptor QDs. Current density-voltage characteristics describes the greater V oc and I sc in the 60 wt% CuInS2 QDs based solar cell as compared to the low wt% of QDs in the active layer.

Nanomechanical properties of thick porous silicon layers grown on p- and p+-type bulk crystalline Si

International Nuclear Information System (INIS)

Charitidis, C.A.; Skarmoutsou, A.; Nassiopoulou, A.G.; Dragoneas, A.

2011-01-01

Highlights: → The nanomechanical properties of bulk crystalline Si. → The nanomechanical properties of porous Si. → The elastic-plastic deformation of porous Si compared to bulk crystalline quantified by nanoindentation data analysis. - Abstract: The nanomechanical properties and the nanoscale deformation of thick porous Si (PSi) layers of two different morphologies, grown electrochemically on p-type and p+-type Si wafers were investigated by the depth-sensing nanoindentation technique over a small range of loads using a Berkovich indenter and were compared with those of bulk crystalline Si. The microstructure of the thick PSi layers was characterized by field emission scanning electron microscopy. PSi layers on p+-type Si show an anisotropic mesoporous structure with straight vertical pores of diameter in the range of 30-50 nm, while those on p-type Si show a sponge like mesoporous structure. The effect of the microstructure on the mechanical properties of the layers is discussed. It is shown that the hardness and Young's modulus of the PSi layers exhibit a strong dependence on their microstructure. In particular, PSi layers with the anisotropic straight vertical pores show higher hardness and elastic modulus values than sponge-like layers. However, sponge-like PSi layers reveal less plastic deformation and higher wear resistance compared with layers with straight vertical pores.

First-principles study on electronic, optic, elastic, dynamic and thermodynamic properties of RbH compound

Directory of Open Access Journals (Sweden)

Gulebaglan Sinem Erden

2015-01-01

Full Text Available We performed first-principles calculations to obtain the electronic, optical, elastic, lattice-dynamical and thermodynamic properties of RbH compound with rock salt structure. The ground-state properties, i.e., the lattice constant and the band gap were investigated using a plane wave pseudopotential method within density functional theory. The calculated lattice constant, bulk modulus, energy band gap and elastic constants are reported and compared with previous theoretical and experimental results. Our calculated results and the previous results which are obtained from literature are in a good agreement. Moreover, real and imaginary parts of complex dielectric function, reflectivity spectrum, absorption, extinction coefficient and loss function as a function of photon energy and refractive index with respect to photon wavelength were calculated. In addition, temperature dependent thermodynamic properties such as Helmholtz free energy, internal energy, entropy and specific heat have been studied.

Short optical pulse generation at 40 GHz with a bulk electro-absorption modulator packaged device

Science.gov (United States)

Langlois, Patrick; Moore, Ronald; Prosyk, Kelvin; O'Keefe, Sean; Oosterom, Jill A.; Betty, Ian; Foster, Robert; Greenspan, Jonathan; Singh, Priti

2003-12-01

Short optical pulse generation at 40GHz and 1540nm wavelength is achieved using fully packaged bulk quaternary electro-absorption modulator modules. Experimental results obtained with broadband and narrowband optimized packaged modules are presented and compared against empirical model predictions. Pulse duty cycle, extinction ratio and chirp are studied as a function of sinusoidal drive voltage and detuning between operating wavelength and modulator absorption band edge. Design rules and performance trade-offs are discussed. Low-chirp pulses with a FWHM of ~12ps and sub-4ps at a rate of 40GHz are demonstrated. Optical time-domain demultiplexing of a 40GHz to a 10GHz pulse train is also demonstrated with better than 20dB extinction ratio.

Optical properties of marine waters and the development of bio-optical algorithms

Digital Repository Service at National Institute of Oceanography (India)

Desa, E.

This paper presents the primary optical variables used in the measurement of the optical properties of marine waters. How can in-situ measurements be used in the optical recognition of coastal and open ocean waters. We then look at bio...

Effect of conduction band nonparabolicity on the optical properties in ...

Indian Academy of Sciences (India)

the bulk conduction band edge, the correction due to nonparabolicity can be important. [9,10]. In a narrow QW under a strong magnetic field, the optical absorption coefficients calculated with the nonparabolicity correction shows remarkable deviation from results obtained using parabolic energy approximation [11].

Computational studies of third-order nonlinear optical properties of ...

Indian Academy of Sciences (India)

Anuj Kumar

2017-06-20

Jun 20, 2017 ... Department of Physics, Jaypee University of Engineering and Technology, Raghogarh,. Guna 473 226, India. ∗ ... properties and other molecular properties of the organic nonlinear optical crystal 2-aminopyridinium p- toluenesulphonate ... nal processing, optical limiting, optical logic gates, laser radiation ...

Optical properties of monodispersive FePt nanoparticle films

Energy Technology Data Exchange (ETDEWEB)

Lee, S.J.; Lo, C.C.H. [Ames Laboratory, Iowa State University, Ames, IA 50011 (United States); Yu, A.C.C. [Sony Corporation, Sendai Technology Center, 3-4-1 Sakuragi, Miyagi 985-0842 (Japan); Fan, M. [Center for Sustainable Environmental Technologies, Iowa State University, Ames, IA 50011 (United States)

2004-10-01

The optical properties of monodispersive FePt nanoparticle films were investigated using spectroscopic ellipsometry in the energy range of 1.5 to 5.5 eV. The monodispersive FePt nanoparticle film was stabilized on a Si substrate by means of an organosilane coupling film, resulting in the formation of a (Si/SiO{sub 2}/APTS/FePt nanoparticles monolayer) structure. Multilayer optical models were employed to study the contribution of the FePt nanoparticles to the measured optical properties of the monodispersive FePt nanoparticle film, and to estimate the optical properties of the FePt nanoparticle layer. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Theory of the optical and microwave properties of metal-dielectric films

International Nuclear Information System (INIS)

Sarychev, A.K.; Bergman, D.J.; Yagil, Y.

1995-01-01

We present a detailed theoretical study of the high frequency response of thin, metal-dielectric inhomogeneous films. Semicontinuous metal films are normally prepared by thermal evaporation or sputtering of the metal on an insulating substrate. The optical properties of such films show anomalous phenomena, which are absent in both the bulk metal and the bulk insulator. Our approach is based upon a direct solution of Maxwell's equations, without having to invoke the quasi-static approximation. Electric and magnetic fields outside the film are related to the currents inside the film. The electromagnetic properties of semicontinuous films are described by two Ohmic parameters, in contrast with the usual description by a single complex conductivity. Our theory reproduces most of the known experimental data. For example, we are able to explain a prominent absorption band near the percolation threshold, which was observed previously in such systems, as well as some other peculiar features of the reflectance and transmittance. We find that metal-dieletric films can exhibit very interesting properties when there is a strong skin effect in the metal grains. The surface conductivity has a universal value c/(2π) at the percolation threshold. We predict that under such conditions the absorptance A, as a funciton of the metal concentration, is dome shaped with sharp edges. It has a maximum at the percolation threshold and its value at this point is universal, namely A=0.5, while the reflectance R and transmittance T have the equal universal value R=T=0.25. This approach can be extended to semicontinuous superconducting films. Such films are also expected to have a well defined absorption band near the percolation threshold. We believe that such a threshold can be approached not only by decreasing the superconductor concentration but also by increasing the temperature towards and above the critical temperature

Mechanical, electronic, chemical bonding and optical properties of cubic BaHfO3: First-principles calculations

International Nuclear Information System (INIS)

Liu Qijun; Liu Zhengtang; Feng Liping; Tian Hao

2010-01-01

We have performed ab-initio total energy calculations using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory (DFT) to study structural parameters, mechanical, electronic, chemical bonding and optical properties of cubic BaHfO 3 . The calculated lattice parameter and independent elastic constants are in good agreement with previous theoretical and experimental work. The bulk, shear and Young's modulus, Poisson coefficient, compressibility and Lame constants are obtained using Voigt-Reuss-Hill method and the Debye temperature is estimated using Debye-Grueneisen model, which are consistent with previous results. Electronic and chemical bonding properties have been studied from the calculations of band structure, density of states and charge densities. Furthermore, in order to clarify the mechanism of optical transitions of cubic BaHfO 3 , the complex dielectric function, refractive index, extinction coefficient, reflectivity, absorption efficient, loss function and complex conductivity function are calculated. Then, we have explained the origins of spectral peaks on the basis of the theory of crystal-field and molecular-orbital bonding.

Spectroscopic properties of rare earths in optical materials

CERN Document Server

Parisi, Jürgen; Osgood, R; Warlimont, Hans; Liu, Guokui; Jacquier, Bernard

2005-01-01

Aimed at researchers and graduate students, this book provides up-to-date information for understanding electronic interactions that impact the optical properties of rare earth ions in solids. Its goal is to establish a connection between fundamental principles and the materials properties of rare-earth activated luminescent and laser optical materials. The theoretical survey and introduction to spectroscopic properties include electronic energy level structure, intensities of optical transitions, ion-phonon interactions, line broadening, and energy transfer and up-conversion. An important aspect of the book lies in its deep and detailed discussions on materials properties and the potential of new applications such as optical storage, information processing, nanophotonics, and molecular probes that have been identified in recent experimental studies. This volume will be a valuable reference book on advanced topics of rare earth spectroscopy and materials science.

First-principles investigation of the optical properties for rocksalt mixed metal oxide Mg{sub x}Zn{sub 1−x}O

Energy Technology Data Exchange (ETDEWEB)

Hadjab, Moufdi [Applied Materials Laboratory, Research Center, University Djillali Liabes, 22000, Sidi Bel Abbes (Algeria); Thin Films Development and Applications Unit UDCMA, Setif – Research Center in Industrial Technologies CRTI, P. O. Box 64, Cheraga, 16014, Algiers (Algeria); Berrah, Smail [Mastery Renewable Energies Laboratory (LMER), University of A. Mira, Bejaia (Algeria); Abid, Hamza; Ziane, Mohamed Issam; Bennacer, Hamza [Applied Materials Laboratory, Research Center, University Djillali Liabes, 22000, Sidi Bel Abbes (Algeria); Reshak, Ali H., E-mail: maalidph@yahoo.co.uk [New Technologies – Research Center, University of West Bohemia, Univerzitni 8, 30614, Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007, Kangar, Perlis (Malaysia)

2016-10-01

In this paper, we have presented a theoretical study of the optical properties for the cubic Mg{sub x}Zn{sub 1−x}O (x = 0.0, 0.125, 0.375, 0.625, 0.875 and 1.0) alloys using the full-potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT). The local density approximation (LDA) was applied to calculate the structural properties. In order to explore the desired properties, the Mg{sub x}Zn{sub 1−x}O alloys were modeled at various x compositions from 0.0 to 1.0 by step of 0.125. The recently modified semi-local Becke-Johnson potential with LDA correlation in the form of mBJ-LDA was used to predict the energy band gap, optical dielectric function, refractive index, absorption coefficient, reflectivity, optical conductivity and the electron energy loss of Mg{sub x}Zn{sub 1−x}O alloys. The obtained results show good agreement with the experimental data, which indicate that the investigated ternary alloys are among promising material for the fabrication of electronic, optoelectronic devices and their applications. - Highlights: • Theoretical study of optical properties of the cubic alloy Mg{sub x}Zn{sub 1−x}O. • The lattice constants, the bulk modulus B and it’s pressure derivative B′ were obtained. • The calculated energy gaps within mBJ show good agreement with the experimental data. • The optical properties were calculated and discussed in details.

Designing Optical Properties in DNA-Programmed Nanoparticle Superlattices

Science.gov (United States)

Ross, Michael Brendan

A grand challenge of modern science has been the ability to predict and design the properties of new materials. This approach to the a priori design of materials presents a number of challenges including: predictable properties of the material building blocks, a programmable means for arranging such building blocks into well understood architectures, and robust models that can predict the properties of these new materials. In this dissertation, we present a series of studies that describe how optical properties in DNA-programmed nanoparticle superlattices can be predicted prior to their synthesis. The first chapter provides a history and introduction to the study of metal nanoparticle arrays. Chapter 2 surveys and compares several geometric models and electrodynamics simulations with the measured optical properties of DNA-nanoparticle superlattices. Chapter 3 describes silver nanoparticle superlattices (rather than gold) and identifies their promise as plasmonic metamaterials. In chapter 4, the concept of plasmonic metallurgy is introduced, whereby it is demonstrated that concepts from materials science and metallurgy can be applied to the optical properties of mixed metallic plasmonic materials, unveiling rich and tunable optical properties such as color and asymmetric reflectivity. Chapter 5 presents a comprehensive theoretical exploration of anisotropy (non-spherical) in nanoparticle superlattice architectures. The role of anisotropy is discussed both on the nanoscale, where several desirable metamaterial properties can be tuned from the ultraviolet to near-infrared, and on the mesoscale, where the size and shape of a superlattice is demonstrated to have a pronounced effect on the observed far-field optical properties. Chapter 6 builds upon those theoretical data presented in chapter 5, including the experimental realization of size and shape dependent properties in DNA-programmed superlattices. Specifically, nanoparticle spacing is explored as a parameter that

Optical Properties of Nanoparticle Systems Mie and Beyond

CERN Document Server

Quinten, Michael

2011-01-01

Unlike other books who concentrate on metallic nanoparticles with sizes less than 100 nm, the author discusses optical properties of particles with (a) larger size and (b) of any material. The intention of this book is to fill the gap in the description of the optical properties of small particles with sizes less than 1000 nm and to provide a comprehensive overview on the spectral behavior of nanoparticulate matter. The author concentrates on the linear optical properties elastic light scattering and absorption of single nanoparticles and on reflectance and transmittance of nanoparticle matter

Photoconductance of Bulk Heterojunctions with Tunable Nanomorphology Consisting of P3HT and Naphtalene Diimide Siloxane Oligomers

NARCIS (Netherlands)

Grzegorczyk, W.J.; Ganesan, P.; Savenije, T.J.; Bavel, van S.; Loos, J.; Sudhölter, E.J.R.; Siebbeles, L.D.A.; Zuilhof, H.

2009-01-01

The relation between the morphology, optical, and photoconductive properties of thin-film bulk heterojunctions of poly(3-hexylthiophene) (P3HT) with a series of electron-accepting siloxanes with a different number (x = 2, 4, 5) of pendant naphthalene diimide (NDIS) moieties is reported. All NDIS

Optical properties of low-dimensional materials

CERN Document Server

Ogawa, T

1998-01-01

This book surveys recent theoretical and experimental studies of optical properties of low-dimensional materials. As an extended version of Optical Properties of Low-Dimensional Materials (Volume 1, published in 1995 by World Scientific), Volume 2 covers a wide range of interesting low-dimensional materials including both inorganic and organic systems, such as disordered polymers, deformable molecular crystals, dilute magnetic semiconductors, SiGe/Si short-period superlattices, GaAs quantum wires, semiconductor microcavities, and photonic crystals. There are excellent review articles by promis

Structural, electrical, and optical properties of polycrystalline NbO{sub 2} thin films grown on glass substrates by solid phase crystallization

Energy Technology Data Exchange (ETDEWEB)

Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), Kawasaki (Japan); Kamisaka, Hideyuki [Department of Chemistry, The University of Tokyo (Japan); Hirose, Yasushi; Hasegawa, Tetsuya [Kanagawa Academy of Science and Technology (KAST), Kawasaki (Japan); Department of Chemistry, The University of Tokyo (Japan)

2017-03-15

We investigated the structural, electrical, and optical properties of polycrystalline NbO{sub 2} thin films on glass substrates. The NbO{sub 2} films were crystallized from amorphous precursor films grown by pulsed laser deposition at various oxygen partial pressures (P{sub O2}). The electrical and optical properties of the precursor films systematically changed with P{sub O2}, demonstrating that the oxygen content of the precursor films can be finely controlled with P{sub O2}. The precursors were crystallized into polycrystalline NbO{sub 2} films by annealing under vacuum at 600 C. The NbO{sub 2} films possessed extremely flat surfaces with branching patterns. Even optimized films showed a low resistivity (ρ) of 2 x 10{sup 2} Ω cm, which is much lower than the bulk value of 1 x 10{sup 4} Ω cm, probably because of the inferior crystallinity of the films compared with that of a bulk NbO{sub 2} crystal. Both oxygen-rich and -poor NbO{sub 2} films showed lower ρ than that of the stoichiometric film. The NbO{sub 2} film with the highest ρ showed an indirect bandgap of 0.7 eV. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

qF-SSOP: real-time optical property corrected fluorescence imaging

Science.gov (United States)

Valdes, Pablo A.; Angelo, Joseph P.; Choi, Hak Soo; Gioux, Sylvain

2017-01-01

Fluorescence imaging is well suited to provide image guidance during resections in oncologic and vascular surgery. However, the distorting effects of tissue optical properties on the emitted fluorescence are poorly compensated for on even the most advanced fluorescence image guidance systems, leading to subjective and inaccurate estimates of tissue fluorophore concentrations. Here we present a novel fluorescence imaging technique that performs real-time (i.e., video rate) optical property corrected fluorescence imaging. We perform full field of view simultaneous imaging of tissue optical properties using Single Snapshot of Optical Properties (SSOP) and fluorescence detection. The estimated optical properties are used to correct the emitted fluorescence with a quantitative fluorescence model to provide quantitative fluorescence-Single Snapshot of Optical Properties (qF-SSOP) images with less than 5% error. The technique is rigorous, fast, and quantitative, enabling ease of integration into the surgical workflow with the potential to improve molecular guidance intraoperatively. PMID:28856038

Linear Optical Properties of Gold Colloid

Directory of Open Access Journals (Sweden)

Jingmin XIA

2015-11-01

Full Text Available Gold colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The morphology, size of gold nanoparticles and the optical property of colloid were characterized by transmission electron microscope and UV-Vis spectrophotometer, respectively. It shows that the gold nanoparticles are in the shape of spheres with diameters less than 8 nm, and the surface plasmon resonance absorption peak is located at about 438 nm. As the volume fraction of gold particles increases, the intensity of absorption peak strengthens. The optical property of gold colloid was analyzed by Maxwell-Garnett (MG effective medium theory in the company of Drude dispersion model. The results show that the matrix dielectric constant is a main factor, which influences the optical property of gold colloid.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9558

Optical properties and photoluminescence of tetrahexyl-sexithiophene allotropes

NARCIS (Netherlands)

Botta, C; Destri, S; Porzio, W; Bongiovanni, G; Loi, MA; Mura, A; Tubino, R

2001-01-01

The optical absorption, Raman scattering and photoluminescence of two phases of tetrahexyl-sexithiophene (4HT6) display properties coherently related to the different molecular conformations imposed by the chain packing. We analyse the temperature dependence of the optical properties of a sample in

Improvement of the mechanical properties of bulk superconductors; Jushiganshin niyoru baruku chodendotai no kikaitekitokusei no kaizen

Energy Technology Data Exchange (ETDEWEB)

Tomita, M; Murakami, M [Superconductivity Research Laboratory, Tokyo (Japan)

1999-11-25

Large single-grain bulk rare earth element (RE)-Ba-Cu-O superconductors can trip large fields exceeding several teslas and thus can function as very strong quasi-permanent magnets. However, the maximum trapped field is essentially limited by the mechanical strength of the bulk superconductors. The stress produced by refrigeration sometimes causes cracking. A large electromagnetic force also acts on superconductors when they trap large magnetic fields, and this occasionally leads to device failure. We have recently found that epoxy resin can penetrate into bulk superconductors under certain conditions. Microstructural observation revealed that microcracks as well as porosities can be impregnated with epoxy resin, which greatly improves the mechanical properties of bulk RE-Ba-Cu-O and thus results in the improvement of field trapping capability. (author)

Composition design and mechanical properties of ternary Cu–Zr–Ti bulk metallic glasses

International Nuclear Information System (INIS)

Pan, Ye; Zeng, Yuqiao; Jing, Lijun; Zhang, Lu; Pi, Jinhong

2014-01-01

Highlights: • Newly designed monolithic bulk metallic glasses are of good glass-forming ability. • Cu 50 Zr 44 Ti 6 exhibits excellent plastic deformation up to ∼7.4%. • Copious and intersected shear bans are observed in the fractography of Cu 50 Zr 44 Ti 6 . • Cu 50 Zr 44 Ti 6 has the best plasticity in the ternary Cu–Zr–Ti bulk metallic glasses. - Abstract: The new compositions of ternary Cu–Zr–Ti bulk metallic glasses are predicted by integrating calculation of vacancy formation energy, mixing enthalpy and configuration entropy of the alloys based on thermodynamics of glass formers. The monolithic amorphous rods of 3 mm diameter have been successfully fabricated, and characterized by X-ray diffractometry, differential scanning calorimetry, scanning electronic microscopy, transmission electronic microscopy and compression tests. The results show that the designed alloys possess good glass forming ability and excellent mechanical properties. The mechanical properties of the samples can be effectively improved by regulating their composition. The monolithic amorphous rod of Cu 50 Zr 44 Ti 6 exhibits a high fracture strength of 1855 MPa and excellent plastic deformation up to ∼7.4%. The formation and propagation of shear bands in samples are also investigated. The enhancement of plastic deformation is mainly contributed to multiplication and intersection of shear bands

Crystal growth and optical properties of 4-aminobenzophenone (ABP)

Science.gov (United States)

Li, Zhengdong; Wu, Baichang; Su, Genbo; Huang, Gongfan

1997-02-01

Bulk crystals of 4-aminobenzophenone (ABP) were grown from organic solution. The crystal structure was determined by X-ray analysis. The refractive indices were determined by the method of prism minimum deviation. Some effective nonlinear-optical coefficients deff were measured. A blue second-harmonic emission with wavelengths of 433 and 460 nm were observed during laser diode pumping.

Nonlinear optical properties of TeO$_2$ crystalline phases from first principles

OpenAIRE

Berkaine, Nabil; Orhan, Emmanuelle; Masson, Olivier; Thomas, Philippe; Junquera, Javier

2010-01-01

We have computed second and third nonlinear optical susceptibilities of two crystalline bulk tellurium oxide polymorphs: $\\alpha$-TeO$_{2}$ (the most stable crystalline bulk phase) and $\\gamma$-TeO$_{2}$ (the crystalline phase that ressembles the more to the glass phase. Third order nonlinear susceptibilities of the crystalline phases are two orders of magnitude larger than $\\alpha$-SiO$_{2}$ cristoballite, thus extending the experimental observations on glasses to the case of crystalline com...

Iron phosphate glasses: Bulk properties and atomic scale structure

Energy Technology Data Exchange (ETDEWEB)

Joseph, Kitheri; Stennett, Martin C.; Hyatt, Neil C.; Asuvathraman, R.; Dube, Charu L.; Gandy, Amy S.; Govindan Kutty, K. V.; Jolley, Kenny; Vasudeva Rao, P. R.; Smith, Roger

2017-10-01

Bulk properties such as glass transition temperature, density and thermal expansion of iron phosphate glass compositions, with replacement of Cs by Ba, are investigated as a surrogate for the transmutation of 137Cs to 137Ba, relevant to the immobilisation of Cs in glass. These studies are required to establish the appropriate incorporation rate of 137Cs in iron phosphate glass. Density and glass transition temperature increases with the addition of BaO indicating the shrinkage and reticulation of the iron phosphate glass network. The average thermal expansion coefficient reduces from 19.8 × 10-6 K-1 to 13.4 × 10-6 K-1, when 25 wt. % of Cs2O was replaced by 25 wt. % of BaO in caesium loaded iron phosphate glass. In addition to the above bulk properties, the role of Ba as a network modifier in the structure of iron phosphate glass is examined using various spectroscopic techniques. The FeII content and average coordination number of iron in the glass network was estimated using Mössbauer spectroscopy. The FeII content in the un-doped iron phosphate glass and barium doped iron phosphate glasses was 20, 21 and 22 ± 1% respectively and the average Fe coordination varied from 5.3 ± 0.2 to 5.7 ± 0.2 with increasing Ba content. The atomic scale structure was further probed by Fe K-edge X-ray absorption spectroscopy. The average coordination number provided by extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge structure was in good agreement with that given by the Mössbauer data.

Influence of thermal annealing-induced molecular aggregation on film properties and photovoltaic performance of bulk heterojunction solar cells based on a squaraine dye

Science.gov (United States)

Zhang, Pengpeng; Ling, Zhitian; Chen, Guo; Wei, Bin

2018-04-01

Squaraine (SQ) dyes have been considered as efficient photoactive materials for organic solar cells. In this work, we purposely controlled the molecular aggregation of an SQ dye, 2,4-bis[4-(N,N-dibutylamino)-2-dihydroxyphenyl] SQ (DBSQ-(OH)2) in the DBSQ(OH)2:[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend film by using the thermal annealing method, to study the influence of the molecular aggregation on film properties as well as the photovoltaic performance of DBSQ(OH)2:PCBM-based bulk heterojunction (BHJ) solar cells. Our results demonstrate that thermal annealing may change the aggregation behavior of DBSQ(OH)2 in the DBSQ(OH)2:PCBM film, and thus significantly influence the surface morphology, optical and electrical properties of the blend film, as well as the photovoltaic performance of DBSQ(OH)2:PCBM BHJ cells.

Structural and optical properties of novel surfactant-coated Yb-TiO2 nanoparticles

International Nuclear Information System (INIS)

Calandra, P.; Lombardo, D.; Pistone, A.; Turco Liveri, V.; Trusso, S.

2011-01-01

In this paper a novel hybrid approach to synthesise composite nanoparticles is presented. It is based on the laser ablation of a bulk target (Yb) immersed in a reversed micellar solution which contains nanoparticles of a different host material (TiO 2 nanoparticles) previously synthesised by chemical method. This approach thus exploits the advantages of the chemical synthesis through reversed micellar solution (size control, nanoparticle stabilisation), and of the laser ablation (“clean” synthesis, no side reactions). Central role is played by the microscopic processes controlling the deposition of the ablated Yb atoms onto the surface of TiO 2 nanoparticles which actually behave as nucleation seeds. The structural features of the resulting Yb-TiO 2 composite nanoparticles have been studied by Transmission Electron Microscopy, whereas their peculiar optical properties have been explored by UV–Vis spectroscopy and steady-state fluorescence. Results consistently show the formation of Yb and TiO 2 glued nanodomains to form nearly spherical and non-interacting nanoparticles with enhanced photophysical properties.

Microwave processed bulk and nano NiMg ferrites: A comparative study on X-band electromagnetic interference shielding properties

Energy Technology Data Exchange (ETDEWEB)

Chandra Babu Naidu, K., E-mail: chandrababu954@gmail.com [Ceramic Composite Laboratory, Centre for Crystal Growth, SAS, VIT University, Vellore 632014, Tamilnadu (India); Madhuri, W., E-mail: madhuriw12@gmail.com [Ceramic Composite Laboratory, Centre for Crystal Growth, SAS, VIT University, Vellore 632014, Tamilnadu (India); IFW, Leibniz Institute for Solid State and Materials Research, Technische Universität Dresden, 01069 Dresden (Germany)

2017-02-01

Bulk and nano Ni{sub 1-x}Mg{sub x}Fe{sub 2}O{sub 4} (x = 0–1) samples were synthesized via microwave double sintering and microwave assisted hydrothermal techniques respectively. The diffraction pattern confirmed the formation of cubic spinel phases in case of both the ferrites. The larger bulk densities were achieved to the bulk than that of nano. In addition, a comparative study on X-band (8.4–12 GHz) electromagnetic interference shielding properties of current bulk and nanomaterials was elucidated. The results showed that the bulk Ni{sub 0.6}Mg{sub 0.4}Fe{sub 2}O{sub 4} composition revealed the highest total shielding efficiency (SE{sub T}) of ∼17 dB. In comparison, the shielding efficiency values of all bulk contents were higher than that of nano because of larger bulk densities. Moreover, the ac-electromagnetic parameters such as electrical conductivity (σ{sub ac}), the respective real (ε′ & μ′) and imaginary parts (ε″ & μ″) of complex permittivity and permeability were investigated as a function of gigahertz frequency. The bulk ferrites of x = 0.4 & 0.6 showed the high ε″ of 10.26 & 6.71 and μ″ of 3.65 & 3.09 respectively at 12 GHz which can work as promising microwave absorber materials. Interestingly, nanoferrites exhibited negative μ″ values at few frequencies due to geometrical effects which improves the microwave absorption. - Highlights: • Bulk and nano NiMg ferrites are prepared by microwave and hydrothermal method. • X-band EMI shielding properties are studied for both bulk and nano ferrites. • Bulk Ni{sub 0.6}Mg{sub 0.4}Fe{sub 2}O{sub 4} revealed the highest SE{sub T} of ∼17 dB at 8.4 GHz. • Bulk x = 0.4 & 0.6 showed the high ε″ and μ″ at 12 GHz for absorber applications.

Inside Perovskites: Quantum Luminescence from Bulk Cs4PbBr6 Single Crystals

KAUST Repository

de Bastiani, Michele

2017-08-01

Zero-dimensional perovskite-related structures (0D-PRS) are a new frontier of perovskite-based materials. 0D-PRS, commonly synthesized in powder form, manifest distinctive optical properties such as strong photoluminescence (PL), narrow emission linewidth, and high exciton binding energy. These properties make 0D-PRS compelling for several types of optoelectronic applications, including phosphor screens and electroluminescent devices. However, it would not be possible to rationally design the chemistry and structure of these materials, without revealing the origins of their optical behaviour, which is contradictory to the well-studied APbX3 perovskites. In this work, we synthesize single crystals of Cs4PbBr6 0D-PRS, and investigated the origins of their unique optical and electronic properties. The crystals exhibit a PL quantum yield higher than 40%, the highest reported for perovskite-based single crystals. Time-resolved and temperature dependent PL studies, supported by DFT calculations, and structural analysis, elucidate an emissive behaviour reminiscent of a quantum confined structure rather than a typical bulk perovskite material.

Optical Properties of Hybrid Nanomaterials

Indian Academy of Sciences (India)

owner

K. George Thomas. Photosciences & Photonics Group. National Institute for Interdisciplinary. Science and Technology (NIIST), CSIR,. Trivandrum- 695 019, INDIA. (kgt@vsnl.com). Optical Properties of Hybrid. Nanomaterials ...

Ex vivo investigation of tissue optical properties using an optical fibre sensor

OpenAIRE

Warncke, Dennis

2014-01-01

peer-reviewed Biomedical research has become a strong growing sector in recent years. Moreover the interdisciplinary background involves novel possibilities and measurement techniques. Light propagation in turbid media like human tissue is a central aspect to many medical and biomedical applications. This is a very complex process and depends on parameters, which are called optical properties. The spatial distribution of light is determined by those optical properties. A maj...

Gate-tunable gigantic changes in lattice parameters and optical properties in VO2

Science.gov (United States)

Nakano, Masaki; Okuyama, Daisuke; Shibuya, Keisuke; Ogawa, Naoki; Hatano, Takafumi; Kawasaki, Masashi; Arima, Taka-Hisa; Iwasa, Yoshihiro; Tokura, Yoshinori

2014-03-01

The field-effect transistor provides an electrical switching function of current flowing through a channel surface by external gate voltage (VG). We recently reported that an electric-double-layer transistor (EDLT) based on vanadium dioxide (VO2) enables electrical switching of the metal-insulator phase transition, where the low-temperature insulating state can be completely switched to the metallic state by application of VG. Here we demonstrate that VO2-EDLT enables electrical switching of lattice parameters and optical properties as well as electrical current. We performed in-situ x-ray diffraction and optical transmission spectroscopy measurements, and found that the c-axis length and the infrared transmittance of VO2 can be significantly modulated by more than 1% and 40%, respectively, by application of VG. We emphasize that these distinguished features originate from the electric-field induced bulk phase transition available with VO2-EDLT. This work was supported by the Japan Society for the Promotion of Science (JSPS) through its ``Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program).''

Temperature dependence of the bulk and surface properties of liquid Zn-Cd alloys

Energy Technology Data Exchange (ETDEWEB)

Awe, O.E. [University of Ibadan, Department of Physics, Ibadan (Nigeria); Azeez, A.A. [African University of Science and Technology, Abuja (Nigeria)

2017-05-15

The effects of temperature on the bulk and surface properties of liquid Zn-Cd alloys have been theoretically investigated, using a combination of self association model, Darken's thermodynamic equation for diffusion, empirical model for viscosity and a statistical mechanics model. The results from this study show that change in temperature resulted in cross-over effects in bulk and surface properties. We also found that with an increase in temperature, a pronounced asymmetry of viscosity isotherm is significantly reduced, and viscosity isotherm exhibited anomalous behaviour. Our results reveal that the homocoordination tendency in Zn-Cd liquid alloys is not strong and reduces with increasing temperature. The study further suggests a pronounced segregation of Cd-atoms at the surface of Zn-Cd liquid alloys and the extent of segregation reduces with temperature. We as well found that, in addition to the reported understanding that size-factor determines the compositional location of asymmetry of the viscosity isotherm, temperature is an operating parameter that has effect, not only on the composition of asymmetry, but also on the magnitude of asymmetry. In all the properties investigated, the most pronounced effect of temperature (52.9 %) is on the viscosity while the least effect (7.1 %) is on the surface tension. (orig.)

Enhancement of the optical and electrical properties of ITO thin films deposited by electron beam evaporation technique

Science.gov (United States)

Ali, H. M.; Mohamed, H. A.; Mohamed, S. H.

2005-08-01

Indium tin oxide (ITO) is widely utilized in numerous industrial applications due to its unique combined properties of transparency to visible light and electrical conductivity. ITO films were deposited on glass substrates by an electron beam evaporation technique at room temperature from bulk samples, with different thicknesses. The film with 1500 Å thick was selected to perform annealing in the temperature range of 200 400 °C and annealing for varying times from 15 to 120 min at 400 °C. The X-ray diffraction of the films was analyzed in order to investigate its dependence on thickness, and annealing. Electrical and optical measurements were also carried out. Transmittance, optical energy gap, refractive index, carrier concentration, thermal emissivity and resistivity were investigated. It was found that the as-deposited films with different thicknesses were highly absorbing and have relatively poor electrical properties. The films become opaque with increasing the film thickness. After thermal annealing, the resistance decreases and a simultaneous variation in the optical transmission occurs. A transmittance value of 85.5% in the IR region and 82% in the visible region of the spectrum and a resistivity of 2.8 × 10-4 Ω Cm were obtained at annealing temperature of 400 °C for 120 min.

Photorefractive optics materials, properties, and applications

CERN Document Server

Yu, Francis T S

1999-01-01

The advances of photorefractive optics have demonstrated many useful and practical applications, which include the development of photorefractive optic devices for computer communication needs. To name a couple significant applications: the large capacity optical memory, which can greatly improve the accessible high-speed CD-ROM and the dynamic photorefractive gratings, which can be used for all-optic switches for high-speed fiber optic networks. This book is an important reference both for technical and non-technical staffs who are interested in this field. * Covers the recent development in materials, phenomena, and applications * Includes growth, characterization, dynamic gratings, and liquid crystal PR effect * Includes applications to photonic devices such as large capacity optical memory, 3-D interconnections, and dynamic holograms * Provides the recent overall picture of current trends in photorefractive optics * Includes optical and electronic properties of the materials as applied to dynamic photoref...

Influence of organic solvent on optical and structural properties of ultra-small silicon dots synthesized by UV laser ablation in liquid.

Science.gov (United States)

Intartaglia, Romuald; Bagga, Komal; Genovese, Alessandro; Athanassiou, Athanassia; Cingolani, Roberto; Diaspro, Alberto; Brandi, Fernando

2012-11-28

Ultra small silicon nanoparticles (Si-NPs) with narrow size distribution are prepared in a one step process by UV picosecond laser ablation of silicon bulk in liquid. Characterization by electron microscopy and absorption spectroscopy proves Si-NPs generation with an average size of 2 nm resulting from an in situ photofragmentation effect. In this context, the current work aims to explore the liquid medium (water and toluene) effect on the Si-NPs structure and on the optical properties of the colloidal solution. Si-NPs with high pressure structure (s.g. Fm3m) and diamond-like structure (s.g. Fd3m), in water, and SiC moissanite 3C phase (s.g. F4[combining macron]3m) in toluene are revealed by the means of High-Resolution TEM and HAADF-STEM measurements. Optical investigations show that water-synthesized Si-NPs have blue-green photoluminescence emission characterized by signal modulation at a frequency of 673 cm(-1) related to electron-phonon coupling. The synthesis in toluene leads to generation of Si-NPs embedded in the graphitic carbon-polymer composite which has intrinsic optical properties at the origin of the optical absorption and luminescence of the obtained colloidal solution.

Bright conjugated polymer nanoparticles containing a biodegradable shell produced at high yields and with tuneable optical properties by a scalable microfluidic device.

Science.gov (United States)

Abelha, T F; Phillips, T W; Bannock, J H; Nightingale, A M; Dreiss, C A; Kemal, E; Urbano, L; deMello, J C; Green, M; Dailey, L A

2017-02-02

This study compares the performance of a microfluidic technique and a conventional bulk method to manufacture conjugated polymer nanoparticles (CPNs) embedded within a biodegradable poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide) (PEG 5K -PLGA 55K ) matrix. The influence of PEG 5K -PLGA 55K and conjugated polymers cyano-substituted poly(p-phenylene vinylene) (CN-PPV) and poly(9,9-dioctylfluorene-2,1,3-benzothiadiazole) (F8BT) on the physicochemical properties of the CPNs was also evaluated. Both techniques enabled CPN production with high end product yields (∼70-95%). However, while the bulk technique (solvent displacement) under optimal conditions generated small nanoparticles (∼70-100 nm) with similar optical properties (quantum yields ∼35%), the microfluidic approach produced larger CPNs (140-260 nm) with significantly superior quantum yields (49-55%) and tailored emission spectra. CPNs containing CN-PPV showed smaller size distributions and tuneable emission spectra compared to F8BT systems prepared under the same conditions. The presence of PEG 5K -PLGA 55K did not affect the size or optical properties of the CPNs and provided a neutral net electric charge as is often required for biomedical applications. The microfluidics flow-based device was successfully used for the continuous preparation of CPNs over a 24 hour period. On the basis of the results presented here, it can be concluded that the microfluidic device used in this study can be used to optimize the production of bright CPNs with tailored properties with good reproducibility.

Quantum optical properties in plasmonic systems

Energy Technology Data Exchange (ETDEWEB)

Ooi, C. H. Raymond [Department of Physics, University of Malaya, 50603, Kuala Lumpur (Malaysia)

2015-04-24

Plasmonic metallic particle (MP) can affect the optical properties of a quantum system (QS) in a remarkable way. We develop a general quantum nonlinear formalism with exact vectorial description for the scattered photons by the QS. The formalism enables us to study the variations of the dielectric function and photon spectrum of the QS with the particle distance between QS and MP, exciting laser direction, polarization and phase in the presence of surface plasmon resonance (SPR) in the MP. The quantum formalism also serves as a powerful tool for studying the effects of these parameters on the nonclassical properties of the scattered photons. The plasmonic effect of nanoparticles has promising possibilities as it provides a new way for manipulating quantum optical properties of light in nanophotonic systems.

Determining the properties of dense matter: Superconductivity, bulk viscosity, and light reflection in compact stars

Science.gov (United States)

Good, Gerald J.

In this dissertation, we investigate the properties of matter, denser than nuclei, that exists inside compact stars. First, we examine a mixed superfluid/superconductor system, which likely occurs in neutron star cores. We derive an effective theory of Cooper pair quasiparticles from a microscopic theory of nucleons, and calculate the coupling strengths between quasiparticles. We then calculate the structure of magnetic flux tubes, taking into consideration interactions between neutron and proton Cooper pairs. We find that interactions between the condensates can lead to interesting phenomena and new phases at the border between type-I and type-II behavior. Next, we examine the response of nuclear matter to vibrational modes by calculating the bulk viscosity from purely leptonic processes. We find that for hot neutron stars, the bulk viscosity due to leptons is very small compared to the bulk viscosity due to nucleons, but for cold neutron stars, the leptonic component is dominant. Finally, we derive the reflection and transmission properties of light at boundaries between phases of matter that have two independent U(1) generators, which may exist at the surface of "strange stars" or at boundaries between different phases of matter in a neutron star.

Transport properties of high-temperature superconductors: Surface vs bulk effect

International Nuclear Information System (INIS)

Burlachkov, L.; Koshelev, A.E.; Vinokur, V.M.

1996-01-01

We investigate surface-related transport properties of high-temperature superconductors. We find the mean vortex velocity under applied transport current determined by the activation energies for vortex penetration and exit through the Bean-Livingston barrier. We determine the current distribution between the surfaces of superconductor and the field and current dependencies of the transport activation energies. For a three-dimensional superconductor the transport activation energy, U s 3D , is found to decrease with the external field, H, and transport current, J, as U s 3D ∝H -1/2 and U s 3D ∝J -1/2 , respectively. In the quasi-two-dimensional compounds, U s 2D decays logarithmically with field and current. The interplay between the surface and the bulk contributions to the transport properties, such as current-voltage characteristics, is discussed. copyright 1996 The American Physical Society

Ferromagnetic bulk glassy alloys

International Nuclear Information System (INIS)

Inoue, Akihisa; Makino, Akihiro; Mizushima, Takao

2000-01-01

This paper deals with the review on the formation, thermal stability and magnetic properties of the Fe-based bulk glassy alloys in as-cast bulk and melt-spun ribbon forms. A large supercooled liquid region over 50 K before crystallization was obtained in Fe-(Al, Ga)-(P, C, B, Si), Fe-(Cr, Mo, Nb)-(Al, Ga)-(P, C, B) and (Fe, Co, Ni)-Zr-M-B (M=Ti, Hf, V, Nb, Ta, Cr, Mo and W) systems and bulk glassy alloys were produced in a thickness range below 2 mm for the Fe-(Al, Ga)-(P, C, B, Si) system and 6 mm for the Fe-Co-(Zr, Nb, Ta)-(Mo, W)-B system by copper-mold casting. The ring-shaped glassy Fe-(Al, Ga)-(P, C, B, Si) alloys exhibit much better soft magnetic properties as compared with the ring-shaped alloy made from the melt-spun ribbon because of the formation of the unique domain structure. The good combination of high glass-forming ability and good soft magnetic properties indicates the possibility of future development as a new bulk glassy magnetic material

Effects of seed geometry on the crystal growth and the magnetic properties of single grain REBCO bulk superconductors

Energy Technology Data Exchange (ETDEWEB)

Lee, Hwi Joo; Lee, Hee Gyoun [Korea Polytechnic University, Siheung (Korea, Republic of); Park, Soon Dong; Jun, Bung Hyack; Kim, Chan Joong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2017-09-15

This study presents that the orientation and the geometry of seed affect on the growth behavior of melt processed single grain REBCO bulk superconductor and its magnetic properties. The effects of seed geometry have been investigated for thin 30mm x 30mm rectangular powder compacts. Single grain REBCO bulk superconductors have been grown successfully by a top seed melt growth method for 8-mm thick vertical thin REBCO slab. Asymmetric structures have been developed at the front surface and at the rear surface of the specimen. Higher magnetic properties have been obtained for the specimen that c-axis is normal to the specimen surface. The relationships between microstructure, grain growth and magnetic properties have been discussed.

Thermoelectric response of bulk and monolayer MoSe2 and WSe2

KAUST Repository

Sarath Kumar, S. R.

2015-02-24

We study the thermoelectric properties of bulk and monolayer MoSe2 and WSe2 by first-principles calculations and semiclassical Boltzmann transport theory. The lattice thermal conductivity is calculated using the self-consistent iterative approach as well as the single-mode relaxation time approximation. The acoustical and optical contributions to the lattice thermal conductivity are evaluated along with the influence of the phonon mean free path. The employed methodology enables a quantitative comparison of the thermoelectric properties of transition-metal dichalcogenides. In particular, WSe2 is found to be superior to MoSe2 for thermoelectric applications.

Thermoelectric response of bulk and monolayer MoSe2 and WSe2

KAUST Repository

Sarath Kumar, S. R.; Schwingenschlö gl, Udo

2015-01-01

We study the thermoelectric properties of bulk and monolayer MoSe2 and WSe2 by first-principles calculations and semiclassical Boltzmann transport theory. The lattice thermal conductivity is calculated using the self-consistent iterative approach as well as the single-mode relaxation time approximation. The acoustical and optical contributions to the lattice thermal conductivity are evaluated along with the influence of the phonon mean free path. The employed methodology enables a quantitative comparison of the thermoelectric properties of transition-metal dichalcogenides. In particular, WSe2 is found to be superior to MoSe2 for thermoelectric applications.

Characterization of temperature-dependent optical material properties of polymer powders

Energy Technology Data Exchange (ETDEWEB)

Laumer, Tobias [Bayerisches Laserzentrum GmbH, 91052 Erlangen (Germany); SAOT Erlangen Graduate School in Advanced Optical Technologies, 91052 Erlangen (Germany); CRC Collaborative Research Center 814 - Additive Manufacturing, 91052 Erlangen (Germany); Stichel, Thomas; Bock, Thomas; Amend, Philipp [Bayerisches Laserzentrum GmbH, 91052 Erlangen (Germany); CRC Collaborative Research Center 814 - Additive Manufacturing, 91052 Erlangen (Germany); Schmidt, Michael [Bayerisches Laserzentrum GmbH, 91052 Erlangen (Germany); University of Erlangen-Nürnberg, Institute of Photonic Technologies, 91052 Erlangen (Germany); SAOT Erlangen Graduate School in Advanced Optical Technologies, 91052 Erlangen (Germany); CRC Collaborative Research Center 814 - Additive Manufacturing, 91052 Erlangen (Germany)

2015-05-22

In former works, the optical material properties of different polymer powders used for Laser Beam Melting (LBM) at room temperature have been analyzed. With a measurement setup using two integration spheres, it was shown that the optical material properties of polymer powders differ significantly due to multiple reflections within the powder compared to solid bodies of the same material. Additionally, the absorption behavior of the single particles shows an important influence on the overall optical material properties, especially the reflectance of the powder bed. Now the setup is modified to allow measurements at higher temperatures. Because crystalline areas of semi-crystalline thermoplastics are mainly responsible for the absorption of the laser radiation, the influence of the temperature increase on the overall optical material properties is analyzed. As material, conventional polyamide 12 and polypropylene as new polymer powder material, is used. By comparing results at room temperature and at higher temperatures towards the melting point, the temperature-dependent optical material properties and their influence on the beam-matter interaction during the process are discussed. It is shown that the phase transition during melting leads to significant changes of the optical material properties of the analyzed powders.

Ab initio studies of structural, electronic, optical, elastic and thermal properties of silver gallium dichalcogenides (AgGaX2: X = S, Se, Te)

International Nuclear Information System (INIS)

Sharma, Sheetal; Verma, A.S.; Jindal, V.K.

2014-01-01

Graphical abstract: - Highlights: • FP-LAPW method has been used to compute the solid state properties of AgGaX 2 (X = S, Se, Te). • Electronic and optical properties reported with recently developed mBJ potential. • Thermal expansion, heat capacity, Debye temperature, entropy and Grüneisen parameter were evaluated. • Hardness was calculated for the first time at different temperature and pressure. - Abstract: We have performed ab initio calculations for the structural, electronic, optical, elastic and thermal properties of the silver gallium dichalcogenides (AgGaX 2 : X = S, Se, Te). In this study, we have used the accurate full potential linearized augmented plane wave (FP-LAPW) method to find the equilibrium structural parameters and to compute the six elastic constants (C 11 , C 12 , C 13 , C 33 , C 44 and C 66 ). We have reported electronic and optical properties with the recently developed density functional theory of Tran and Blaha, and this theory is used along with the Wu-Cohen generalized gradient approximation (WC-GGA) for the exchange-correlation potential. Furthermore, optical features such as dielectric functions, refractive indices, extinction coefficient, optical reflectivity, absorption coefficients and optical conductivities were calculated for photon energies up to 40 eV. The thermodynamical properties such as thermal expansion, heat capacity, debye temperature, entropy, Grüneisen parameter and bulk modulus were calculated employing the quasi-harmonic Debye model at different temperatures (0–900 K) and pressures (0–8 GPa) and the silent results were interpreted. Hardness of the materials was calculated for the first time at different temperatures and pressures

Optical properties of the human round window membrane

Science.gov (United States)

Höhl, Martin; DeTemple, Daphne; Lyutenski, Stefan; Leuteritz, Georg; Varkentin, Arthur; Schmitt, Heike Andrea; Lenarz, Thomas; Roth, Bernhard; Meinhardt-Wollweber, Merve; Morgner, Uwe

2017-10-01

Optical techniques are effective tools for diagnostic applications in medicine and are particularly attractive for the noninvasive analysis of biological tissues and fluids in vivo. Noninvasive examinations of substances via a fiber optic probe need to consider the optical properties of biological tissues obstructing the optical path. This applies to the analysis of the human perilymph, which is located behind the round window membrane. The composition of this inner ear liquid is directly correlated to inner ear hearing loss. In this work, experimental methods for studying the optical properties of the human round window membrane ex vivo are presented. For the first time, a comprehensive investigation of this tissue is performed, including optical transmission, forward scattering, and Raman scattering. The results obtained suggest the application of visible wavelengths (>400 nm) for investigating the perilymph behind the round window membrane in future.

Ab-initio investigations of the electronic properties of bulk wurtzite Beryllia and its derived nanofilms

KAUST Repository

Goumri-Said, Souraya; Kanoun, Mohammed

2010-01-01

In this Letter we investigate the electronic properties of the bulk and the nanofilm BeO in wurtzite structure. We performed a first-principles pseudo-potential method within the generalized gradient approximation. We will give more importance

Photoelectric Properties of Silicon Nanocrystals/P3HT Bulk-Heterojunction Ordered in Titanium Dioxide Nanotube Arrays

Directory of Open Access Journals (Sweden)

Švrček Vladimir

2009-01-01

Full Text Available Abstract A silicon nanocrystals (Si-ncs conjugated-polymer-based bulk-heterojunction represents a promising approach for low-cost hybrid solar cells. In this contribution, the bulk-heterojunction is based on Si-ncs prepared by electrochemical etching and poly(3-hexylthiophene (P3HT polymer. Photoelectric properties in parallel and vertical device-like configuration were investigated. Electronic interaction between the polymer and surfactant-free Si-ncs is achieved. Temperature-dependent photoluminescence and transport properties were studied and the ratio between the photo- and dark-conductivity of 1.7 was achieved at ambient conditions. Furthermore the porous titanium dioxide (TiO2 nanotubes’ template was used for vertical order of photosensitive Si-ncs/P3HT-based blend. The anodization of titanium foil in ethylene glycol-based electrolyte containing fluoride ions and subsequent thermal annealing were used to prepare anatase TiO2nanotube arrays. The arrays with nanotube inner diameter of 90 and 50 nm were used for vertical ordering of the Si-ncs/P3HT bulk-heterojunction.

Electronic, structural, and optical properties of crystalline yttria

International Nuclear Information System (INIS)

Xu, Y.; Gu, Z.; Ching, W.Y.

1997-01-01

The electronic structure of crystalline Y 2 O 3 is investigated by first-principles calculations within the local-density approximation (LDA) of the density-functional theory. Results are presented for the band structure, the total density of states (DOS), the atom- and orbital-resolved partial DOS, effective charges, bond order, and charge-density distributions. Partial covalent character in the Y-O bonding is shown, and the nonequivalency of the two Y sites is demonstrated. The calculated electronic structure is compared with a variety of available experimental data. The total energy of the crystal is calculated as a function of crystal volume. A bulk modulus B of 183 Gpa and a pressure coefficient B ' of 4.01 are obtained, which are in good agreement with compression data. An LDA band gap of 4.54 eV at Γ is obtained which increases with pressure at a rate of dE g /dP=0.012eV/Gpa at the equilibrium volume. Also investigated are the optical properties of Y 2 O 3 up to a photon energy of 20 eV. The calculated complex dielectric function and electron-energy-loss function are in good agreement with experimental data. A static dielectric constant of var-epsilon(0)=3.20 is obtained. It is also found that the bottom of the conduction band consists of a single band, and direct optical transition at Γ between the top of the valence band and the bottom of the conduction band may be symmetry forbidden. copyright 1997 The American Physical Society

Bulk-Like Electrical Properties Induced by Contact-Limited Charge Transport in Organic Diodes: Revised Space Charge Limited Current

KAUST Repository

Xu, Guangwei

2018-02-22

Charge transport governs the operation and performance of organic diodes. Illuminating the charge-transfer/transport processes across the interfaces and the bulk organic semiconductors is at the focus of intensive investigations. Traditionally, the charge transport properties of organic diodes are usually characterized by probing the current–voltage (I–V) curves of the devices. However, to unveil the landscape of the underlying potential/charge distribution, which essentially determines the I–V characteristics, still represents a major challenge. Here, the electrical potential distribution in planar organic diodes is investigated by using the scanning Kelvin probe force microscopy technique, a method that can clearly separate the contact and bulk regimes of charge transport. Interestingly, by applying to devices based on novel, high mobility organic materials, the space-charge-limited-current-like I–V curves, which are previously believed to be a result of the bulk transport, are surprisingly but unambiguously demonstrated to be caused by contact-limited conduction. A model accounting is developed for the transport properties of both the two metal/organic interfaces and the bulk. The results indicate that pure interface-dominated transport can indeed give rise to I–V curves similar to those caused by bulk transport. These findings provide a new insight into the charge injection and transport processes in organic diodes.

The applicability of physical optics in the millimetre and sub-millimetre spectral region. Part I: The ray tracing with diffraction on facets method

Science.gov (United States)

Baran, A. J.; Hesse, Evelyn; Sourdeval, Odran

2017-03-01

Future satellite missions, from 2022 onwards, will obtain near-global measurements of cirrus at microwave and sub-millimetre frequencies. To realise the potential of these observations, fast and accurate light-scattering methods are required to calculate scattered millimetre and sub-millimetre intensities from complex ice crystals. Here, the applicability of the ray tracing with diffraction on facets method (RTDF) in predicting the bulk scalar optical properties and phase functions of randomly oriented hexagonal ice columns and hexagonal ice aggregates at millimetre frequencies is investigated. The applicability of RTDF is shown to be acceptable down to size parameters of about 18, between the frequencies of 243 and 874 GHz. It is demonstrated that RTDF is generally well within about 10% of T-matrix solutions obtained for the scalar optical properties assuming hexagonal ice columns. Moreover, on replacing electromagnetic scalar optical property solutions obtained for the hexagonal ice aggregate with the RTDF counterparts at size parameter values of about 18 or greater, the bulk scalar optical properties can be calculated to generally well within ±5% of an electromagnetic-based database. The RTDF-derived bulk scalar optical properties result in brightness temperature errors to generally within about ±4 K at 874 GHz. Differing microphysics assumptions can easily exceed such errors. Similar findings are found for the bulk scattering phase functions. This finding is owing to the scattering solutions being dominated by the processes of diffraction and reflection, both being well described by RTDF. The impact of centimetre-sized complex ice crystals on interpreting cirrus polarisation measurements at sub-millimetre frequencies is discussed.

Elastic and optical properties of Ge x Se 2 Sb 1

Indian Academy of Sciences (India)

... E g ) were investigated with high accuracy. The optically determined bulk modulus of these glasses was in good agreement with that elastically investigated. The obtained results were discussed in terms of the changes in the glass density, electronegativity and electronic polarizability with the variation in antimony content.

Near-surface bulk densities of asteroids derived from dual-polarization radar observations

Science.gov (United States)

Virkki, A.; Taylor, P. A.; Zambrano-Marin, L. F.; Howell, E. S.; Nolan, M. C.; Lejoly, C.; Rivera-Valentin, E. G.; Aponte, B. A.

2017-09-01

We present a new method to constrain the near-surface bulk density and surface roughness of regolith on asteroid surfaces using planetary radar measurements. The number of radar observations has increased rapidly during the last five years, allowing us to compare and contrast the radar scattering properties of different small-body populations and compositional types. This provides us with new opportunities to investigate their near-surface physical properties such as the chemical composition, bulk density, porosity, or the structural roughness in the scale of centimeters to meters. Because the radar signal can penetrate into a planetary surface up to a few decimeters, radar can reveal information that is hidden from other ground-based methods, such as optical and infrared measurements. The near-surface structure of asteroids and comets in centimeter-to-meter scale is essential information for robotic and human space missions, impact threat mitigation, and understanding the history of these bodies as well as the formation of the whole Solar System.

Influence of annealing conditions on the optical and structural properties of spin-coated As(2)S(3) chalcogenide glass thin films.

Science.gov (United States)

Song, Shanshan; Dua, Janesha; Arnold, Craig B

2010-03-15

Spin-coating of chalcogenide glass is a low-cost, scalable method to create optical grade thin films, which are ideal for visible and infrared applications. In this paper, we study the influence of annealing on optical parameters of As(2)S(3) films by examining UV-visible and infrared spectroscopy and correlating the results to changes in the physical properties associated with solvent removal. Evaporation of excess solvent results in a more highly coordinated, denser glass network with higher index and lower absorption. Depending on the annealing temperature and time, index values ranging from n = 2.1 to the bulk value (n = 2.4) can be obtained, enabling a pathway to materials optimization.

A confocal optical microscope for detection of single impurities in a bulk crystal at cryogenic temperatures.

Science.gov (United States)

Karlsson, Jenny; Rippe, Lars; Kröll, Stefan

2016-03-01

A compact sample-scanning confocal optical microscope for detection of single impurities below the surface of a bulk crystal at cryogenic temperatures is described. The sample, lens, and scanners are mounted inside a helium bath cryostat and have a footprint of only 19 × 19 mm. Wide field imaging and confocal imaging using a Blu-ray lens immersed in liquid helium are demonstrated with excitation at 370 nm. A spatial resolution of 300 nm and a detection efficiency of 1.6% were achieved.

Electronic, elastic, and optical properties of monolayer BC{sub 2}N

Energy Technology Data Exchange (ETDEWEB)

Jiao, Lina; Hu, Meng; Peng, Yusi; Luo, Yanting; Li, Chunmei; Chen, Zhiqian, E-mail: chen_zq@swu.edu.cn

2016-12-15

The structural stability, electronic structure, elasticity, and optical properties of four types of monolayer BC{sub 2}N have been investigated from first principles using calculation based on density functional theory. The results show that the structural stability of BC{sub 2}N increases with the number of C–C and B–N bonds. By calculating the two-dimensional Young's modulus, shear modulus, Poisson's ratio, and shear anisotropic factors in different directions, four structures present various anisotropies and the most stable structure is almost isotropic. For C-type BC{sub 2}N, the values of two-dimensional Young's modulus, shear modulus, and bulk modulus (309, 128, 195 GPa m{sup −1}), are smaller than those of graphene (343, 151, 208) but bigger than those of h-BN (286, 185, 116). Furthermore, the dielectric function, refractive index, reflectivity, absorption coefficient, and energy loss spectrum are also calculated to investigate the mechanism underpinning the optical transitions in BC{sub 2}N, revealing monolayer BC{sub 2}N as a candidate window material. - Graphical abstract: Schematic diagram of BC{sub 2}N under the biaxial tensile strain. Changes in the valence-band top and the conduction-band bottom of BC{sub 2}N with increasing strain.

First-principles studies of electronic, transport and bulk properties of pyrite FeS2

Directory of Open Access Journals (Sweden)

Dipendra Banjara

2018-02-01

Full Text Available We present results from first principle, local density approximation (LDA calculations of electronic, transport, and bulk properties of iron pyrite (FeS2. Our non-relativistic computations employed the Ceperley and Alder LDA potential and the linear combination of atomic orbitals (LCAO formalism. The implementation of the LCAO formalism followed the Bagayoko, Zhao, and Williams (BZW method, as enhanced by Ekuma and Franklin (BZW-EF. We discuss the electronic energy bands, total and partial densities of states, electron effective masses, and the bulk modulus. Our calculated indirect band gap of 0.959 eV (0.96, using an experimental lattice constant of 5.4166 Å, at room temperature, is in agreement with the measured indirect values, for bulk samples, ranging from 0.84 eV to 1.03 ± 0.05 eV. Our calculated bulk modulus of 147 GPa is practically in agreement with the experimental value of 145 GPa. The calculated, partial densities of states reproduced the splitting of the Fe d bands to constitute the dominant upper most valence and lower most conduction bands, separated by the generally accepted, indirect, experimental band gap of 0.95 eV.

Plasma spray formed near-net-shape MoSi2-Si3N4 bulk nanocomposites-structure property evaluation

International Nuclear Information System (INIS)

Hong, S.J.; Viswanathan, V.; Rea, K.; Patil, S.; Deshpande, S.; Georgieva, P.; McKechnie, T.; Seal, S.

2005-01-01

This article, for the first time, presents the challenges toward the successful consolidation of near-net-shape bulk MoSi 2 -Si 3 N 4 -SiC nanocomposite using plasma spray forming. A detailed characterization of the spray formed bulk nanocomponent has been performed using optical microscopy (OM), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and Vickers hardness testing. Vickers hardness (900 Hv) and fracture toughness (∼>5 MPa m 1/2 ) of the nanocomposite showed a little deviation from the expected, which might be due to the difference in the particle (Si 3 N 4 ) size and their distribution in the MoSi 2 matrix as a function of component thickness. Relatively higher hardness is attributed to the retention of the nanostructure in the composite. In addition, the as fabricated bulk nanocomposite showed enhanced oxidation resistance

Structural and optical properties of electro-optic material. Sputtered (Ba,Sr)TiO3

International Nuclear Information System (INIS)

Suzuki, Masato; Xu, Zhimou; Tanushi, Yuichiro; Yokoyama, Shin

2006-01-01

In order to develop a novel ring resonator optical switch, we have studied the structural and optical properties of the electro-optic material (Ba,Sr)TiO 3 (BST) deposited by RF sputtering on a SiO 2 cladding layer (1.0 μm). The crystallinity of the BST films is evaluated by X-ray diffraction and the optical propagation loss of the waveguides is measured using a He-Ne laser. As a result, it is found that there is a strong relationship between the optical propagation loss and crystallinity of the sputtered film. It is suggested that the propagating light is influenced by the crystal property, for example, the grain size and density of the polycrystalline BST film. (author)

Characterization of CdSe-nanocrystals used in semiconductors for aerospace applications: Production and optical properties

Directory of Open Access Journals (Sweden)

Maroof A. Hegazy

2014-06-01

Full Text Available Semiconductor nanocrystals (NC’s are the materials with dimensions less than 10 nm. When the dimensions of nanocrystals are reduced the bulk bohr diameter, the photo generated electron-hole pair becomes confined and nanocrystal exhibits size dependent upon optical properties. This work is focused on the studying of CdSe semiconductor nanocrystals. These nanocrystals are considered as one of the most widely studies semiconductors because of their size – tunable optical properties from the visible spectrum. CdSe-nanocrystals are produced and obtained throughout the experimental setup initiated at Nano-NRIAG Unit (NNU, which has been constructed and assembled at NRIAG institute. This unit has a specific characterization for preparing chemical compositions, which may be used for solar cell fabrications and space science technology. The materials prepared included cadmium oxide and selinid have sizes ranging between 2.27 nm and 3.75 nm. CdSe-nanocrystals are synthesized in “TOP/TOPO (tri–octyl phosphine/tri–octyl phosphine oxide. Diagnostic tools, include UV analysis, TEM microscope, and X-ray diffraction, which are considered for the analytical studies of the obtained materials. The results show that, in this size regime, the generated particles have unique optical properties, which is achieved from the UV analysis. Also, the TEM image analysis shows the size and shape of the produced particles. These studies are carried out to optimize the photoluminescent efficiency of these nanoparticles. Moreover, the data revealed that, the grain size of nanocrystals is dependent upon the growth time in turn, it leads to a change in the energy gap. Some applications of this class of materials are outlined.

Ultra-violet absorption induced modifications in bulk and nanoscale electrical transport properties of Al-doped ZnO thin films

Energy Technology Data Exchange (ETDEWEB)

Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata, E-mail: tsom@iopb.res.in [SUNAG Laboratory, Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005 (India)

2015-08-07

Using conductive atomic force microscopy and Kelvin probe force microscopy, we study local electrical transport properties in aluminum-doped zinc oxide (ZnO:Al or AZO) thin films. Current mapping shows a spatial variation in conductivity which corroborates well with the local mapping of donor concentration (∼10{sup 20 }cm{sup −3}). In addition, a strong enhancement in the local current at grains is observed after exposing the film to ultra-violet (UV) light which is attributed to persistent photocurrent. Further, it is shown that UV absorption gives a smooth conduction in AZO film which in turn gives rise to an improvement in the bulk photoresponsivity of an n-AZO/p-Si heterojunction diode. This finding is in contrast to the belief that UV absorption in an AZO layer leads to an optical loss for the underneath absorbing layer of a heterojunction solar cell.

Metastability and thermophysical properties of metallic bulk glass forming alloys

International Nuclear Information System (INIS)

Wunderlich, R.K.; Fecht, H.J.

1998-01-01

The absence of crystallization over a wide time/temperature window can be used to produce bulk metallic glass by relatively slow cooling of the melt. For a number of alloys, including several multicomponent Zr-based alloys, the relevant thermodynamic and thermomechanical properties of the metastable glassy and undercooled liquid states have been measured below and above the glass transition temperature. These measurements include specific heat, viscosity, volume, and elastic properties as a function of temperature. As a result, it becomes obvious that the maximum undercooling for these alloys is given by an isentropic condition before an enthalpic or isochoric instability is reached. Alternatively, these glasses can also be produced by mechanical alloying, thus replacing the thermal disorder by static disorder and resulting in the same thermodynamic glass state. During heating through the undercooled liquid, a nanoscale phase separation occurs for most glasses as a precursor of crystallization

Optical and Magnetic Resonance Studies of Na-Diffused ZnO Bulk Single Crystals

Science.gov (United States)

Glaser, E. R.; Garces, N. Y.; Parmar, N. S.; Lynn, K. G.

2013-03-01

Photoluminescence (PL) and optically-detected magnetic resonance (ODMR) at 24 GHz were performed on bulk ZnO crystals after diffusion of Na impurities that were explored as an alternate doping source for p-type conductivity. PL at 2K revealed strong bandedge excitonic recombination at 3.361 eV and a broad ``orange'' PL band at 2.17 eV with FWHM of ~0.5 eV. This ``orange'' emission is very similar to that reported previously[1] from thermoluminescence measurements of intentionally Na-doped bulk ZnO and, thus, strongly suggests the incorporation and activation of the Na-diffused impurities. ODMR performed on this ``orange'' PL revealed two signals. The first was a sharp feature with g-value of ~1.96 and is a well-known ``fingerprint'' of shallow donors in ZnO. The second signal consisted of a pair of lines with an intensity ratio of ~3:1 and with g-tensors (g∥,g⊥ ~2.008-2.029) very similar to ESR signals attributed previously[2] to holes bound to Na impurities located at the axial and non-axial Zn host lattice sites in Na-doped ZnO. Thus, the ``orange'' PL can be tentatively assigned to radiative recombination between residual shallow donors and deep Na-related hole traps.

Optical properties of metals by spectroscopic ellipsometry

International Nuclear Information System (INIS)

Arakawa, E.T.; Inagaki, T.; Williams, M.W.

1979-01-01

The use of spectroscopic ellipsometry for the accurate determination of the optical properties of liquid and solid metals is discussed and illustrated with previously published data for Li and Na. New data on liquid Sn and Hg from 0.6 to 3.7 eV are presented. Liquid Sn is Drude-like. The optical properties of Hg deviate from the Drude expressions, but simultaneous measurements of reflectance and ellipsometric parameters yield consistent results with no evidence for vectorial surface effects

Structure and properties of bulk amorphous magnetically soft coatings prepared by plasma spraying

International Nuclear Information System (INIS)

Kalita, V.I.; Kekalo, I.B.; Komlev, D.I.; Taranichev, V.E.

1995-01-01

Co-Ni-Fe-Si-B composition plasma coatings consisting of amorphous disk-shaped particles forming the bulk of a coating, of crystalline particles and of a threshold space, were studied. Iron and metalloid distribution heterogeneous by the thickness represents a peculiar feature for coating amorphous particles. Structure of coatings and their magnetic properties depend on some technological parameters. Conclusion is made that at annealing the variation of magnetic properties is determined by the processes of directed ordering and stratification of amorphous phase, while the low level of the initial magnetic properties of coatings is caused alongside with structure peculiarities, by occurrence of independent fine-dispersive domain structure in each disk-shaped amorphous phase. 14 refs., 8 figs., 6 tabs

Multilayered nanoclusters of platinum and gold: insights on electrodeposition pathways, electrocatalysis, surface and bulk compositional properties

CSIR Research Space (South Africa)

Mkwizu, TS

2013-06-01

Full Text Available Electrochemical, surface and bulk compositional properties of multilayered nanoclusters of Pt and Au, electrochemically deposited on glassy carbon under conditions involving sequential surface–limited redox–replacement reactions (performed at open...

Investigation of optical properties of Ag: PMMA nanocomposite structures

Science.gov (United States)

Ponelyte, S.; Palevicius, A.; Guobiene, A.; Puiso, J.; Prosycevas, I.

2010-05-01

In the recent years fundamental research involving the nanodimensional materials has received enormous momentum for observing and understanding new types of plasmonic materials and their physical phenomena occurring in the nanoscale. Mechanical and optical properties of these polymer based nanocomposite structures depend not only on type, dimensions and concentration of filler material, but also on a kind of polymer matrix used. By proper selection of polymer matrix and nanofillers, it is possible to engineer nanocomposite materials with certain favorable properties. One of the most striking features of nanocomposite materials is that they can expose unique optical properties that are not intrinsic to natural materials. In these researches, nanocomposite structures were formed using polymer (PMMA) as a matrix, and silver nanoparticles as fillers. By hot embossing procedure a diffraction grating was imprinted on formed layers. The effect of UV exposure time on nanocomposite structures morphology, optical (diffraction effectiveness, absorbance) and mechanical properties was investigated. Results were confirmed by UV-VIS spectrometer, Laser Diffractometer, PMT- 3 and AFM. Investigations proposed new nanocomposite structures as plasmonic materials with improved optical and mechanical properties, which may be applied for a number of technological applications: micro-electro-mechanical devices, optical devices, various plasmonic sensors, or even in DNA nanotechnology.

Electro-optic and magneto-dielectric properties of multifunctional nitride and oxide materials

Science.gov (United States)

Dixit, Ambesh

with a spin polarization of ˜40% +/- 5% , suggesting strong correlation between electron carriers and observed ferromagnetism. Another In-based multifunctional material that has been explored is defect-rich In2O3. This system exhibits numerous interesting properties such as being simultaneously transparent and electrically conducting and above room temperature ferromagnetism together with semiconducting properties. The oxygen stoichiometry in In2O3 plays a crucial role in determining its optical, electronic, and magnetic properties. The effect of oxygen vacancies on different physical properties has been investigated. Our results suggest that as grown, nearly stoichiometric In2O 3 thin films exhibit strong photopersistent current with very long carrier lifetime. Heat treatment under reduced oxygen environment creates oxygen vacancies in these films, producing electron donors. Thus vacuum annealed In2O 3 becomes a highly degenerate n-type conductor. Oxygen deficient In 2O3 can be used as transparent conducting oxide without any further doping, which allows the conductivity to be switched reversibly by thermal annealing in air or vacuum. In addition highly oxygen deficient In 2O3 films exhibit ferromagnetism above room temperature. We have also investigated oxide based magnetoelectric multiferroics which show simultaneous magnetic and ferroelectric properties. This study included detailed investigations of YMnO3, Ni3V2O 8 and FeVO4, where we have investigated FeVO4 a new multiferroic system in the vanadate family. The main focus of this project was to understand the microscopic origin of the magnetoelectric coupling and cross-control of different ferroic order parameters in these system. We have synthesized bulk Ni3V2O8 and FeVO4 ceramics and characterized the thermal, magnetic, dielectric and magnetodielectric response of these samples in bulk form. To understand the cross-control of magnetic and ferroelectric order parameter we deposited thin films of Ni 3V2O8 and Fe

Optical properties of nanoparticles

DEFF Research Database (Denmark)

Bendix, Pól Martin

2015-01-01

At the NBI I am involved in projects relating to optical properties of metallic nanoparticles in particular with respect to plasmonic heating with direct applications to photothermal cancer therapy. For this purpose we have developed heating assays that can be used to measure the heating of any...... nanoscopic heat source like an irradiated nanoparticle...

Enhanced infrared magneto-optical response of the nonmagnetic semiconductor BiTeI driven by bulk Rashba splitting

Energy Technology Data Exchange (ETDEWEB)

Demko, L.; Tokura, Y. [Multiferroics Project, ERATO, JST, c/o Department of Applied Physics, University of Tokyo (Japan); Schober, G.A.H. [Institute for Theoretical Physics, University of Heidelberg (Germany); Kocsis, V.; Kezsmarki, I. [Department of Physics, Budapest University of Technology and Economics and Condensed Matter Research Group of the Hungarian Academy of Sciences (Hungary); Bahramy, M.S.; Murakawa, H. [CMRG and CERG, RIKEN ASI (Japan); Lee, J.S.; Arita, R.; Nagaosa, N. [Department of Applied Physics, University of Tokyo (Japan)

2013-07-01

We study the magneto-optical (MO) response of the polar semiconducting BiTeI with giant bulk Rashba spin splitting at various carrier densities. Despite being nonmagnetic, the material is found to yield a huge MO activity in the infrared region under moderate magnetic fields (up to 3 T). Our first-principles calculations show that the enhanced MO response of BiTeI comes mainly from the intraband transitions between the Rashba-split bulk conduction bands. These transitions connecting electronic states with opposite spin directions become active due to the presence of strong spin-orbit interaction and give rise to distinct features in the MO spectra with a systematic doping dependence. We predict an even more pronounced enhancement in the low-energy MO response and dc Hall effect near the crossing (Dirac) point of the conduction bands.

Preparation, optical properties and 1 Multiplication-Sign 2 polymeric thermo-optic switch of polyurethane-urea

Energy Technology Data Exchange (ETDEWEB)

Qiu, Fengxian, E-mail: fxqiuchem@163.com [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Cao, Zhijuan [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Cao, Guorong; Guan, Yijun; Shen, Qiang [Department of Physics, Jiangsu University, Zhenjiang 212013 (China); Wang, Qing; Yang, Dongya [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China)

2012-08-15

A polyurethane-urea (PUU) containing azo chromophore, polyether polyol (NJ-220) and isophorone diisocyanate (IPDI) was prepared. The structure, thermal property and mechanical properties of obtained PUU were characterized and measured by the UV-visible spectroscopy, Fourier transform infrared, Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The refractive index (n) of PUU was determined at different temperature and wavelength (532 nm, 650 nm and 850 nm) using attenuated total reflection (ATR) technique, and the thermo-optic coefficients (dn/dT) were -5.3643 Multiplication-Sign 10{sup -4} Degree-Sign C{sup -1}, -5.2500 Multiplication-Sign 10{sup -4} Degree-Sign C{sup -1} and -4.6071 Multiplication-Sign 10{sup -4} Degree-Sign C{sup -1}, respectively. Using the Charge Coupled Device (CCD) digital imaging devices, transmission loss of PUU was measured and the value was 0.659 dB cm{sup -1}. A 1 Multiplication-Sign 2 polymeric thermo-optic switch based on the thermo-optic effect of PUU film was proposed. With branching angle of 0.143 Degree-Sign and the finite difference beam propagation method (FD-BPM), the polymeric thermo-optic switch was simulated. The result showed that the power consumption of the thermo-optic switch could be only 0.72 mW, and the response time of the switch was about 3.0 ms. The obtained PUU has a significant improvement in reducing the power consumption and response time compared with those of the normal polymeric thermo-optic switches. -- Highlights: Black-Right-Pointing-Pointer Preparation and structural characterization of a novel azo polyurethane-urea (PUU). Black-Right-Pointing-Pointer The mechanical performance and thermal property of PUU film. Black-Right-Pointing-Pointer The thermo-optic property, transmission loss and dispersion property of PUU. Black-Right-Pointing-Pointer Proposed a new 1 Multiplication-Sign 2 polymeric thermo-optic switch.

Coupled nanopillar waveguides: optical properties and applications

DEFF Research Database (Denmark)

Chigrin, Dmitry N.; Zhukovsky, Sergei V.; Lavrinenko, Andrei

2007-01-01

, while guided modes dispersion is strongly affected by the waveguide structure. We present a systematic analysis of the optical properties of coupled nanopillar waveguides and discuss their possible applications for integrated optics. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim......In this paper we review basic properties of coupled periodic and aperiodic nanopillar waveguides. A coupled nanopillar waveguide consists of several rows of periodically or aperiodically placed dielectric rods (pillars). In such a waveguide, light confinement is due to the total internal reflection...

Mechanisms of the anomalous Pockels effect in bulk water

Science.gov (United States)

Yukita, Shunpei; Suzuki, Yuto; Shiokawa, Naoyuki; Kobayashi, Takayoshi; Tokunaga, Eiji

2018-04-01

The "anomalous" Pockels effect is a phenomenon that a light beam passing between two electrodes in an aqueous electrolyte solution is deflected by an AC voltage applied between the electrodes: the deflection angle is proportional to the voltage such that the incident beam alternately changes its direction. This phenomenon, the Pockels effect in bulk water, apparently contradicts what is believed in nonlinear optics, i.e., macroscopic inversion symmetry should be broken for the second-order nonlinear optical effect to occur such as the first-order electro-optic effect, i.e., the Pockels effect. To clarify the underlying mechanism, the dependence of the effect on the electrode material is investigated to find that the Pockels coefficient with Pt electrodes is two orders of magnitude smaller than with indium tin oxide (ITO) electrodes. It is experimentally confirmed that the Pockels effect of interfacial water in the electric double layer (EDL) on these electrodes shows an electrode dependence similar to the effect in bulk water while the effects depend on the frequency of the AC voltage such that the interfacial signal decreases with frequency but the bulk signal increases with frequency up to 221 Hz. These experimental results lead to a conclusion that the beam deflection is caused by the refractive index gradient in the bulk water region, which is formed transiently by the Pockels effect of interfacial water in the EDL when an AC electric field is applied. The refractive index gradient is caused by the diffuse layer spreading into the bulk region to work as a breaking factor of inversion symmetry of bulk water due to its charge-biased ionic distribution. This mechanism does not contradict the principle of nonlinear optics.

High energy-resolution electron energy-loss spectroscopy study of the dielectric properties of bulk and nanoparticle LaB6 in the near-infrared region

International Nuclear Information System (INIS)

Sato, Yohei; Terauchi, Masami; Mukai, Masaki; Kaneyama, Toshikatsu; Adachi, Kenji

2011-01-01

The dielectric properties of LaB 6 crystals and the plasmonic behavior of LaB 6 nanoparticles, which have been applied to solar heat-shielding filters, were studied by high energy-resolution electron energy-loss spectroscopy (HR-EELS). An EELS spectrum of a LaB 6 crystal showed a peak at 2.0 eV, which was attributed to volume plasmon excitation of carrier electrons. EELS spectra of single LaB 6 nanoparticles showed peaks at 1.1-1.4 eV depending on the dielectric effect from the substrates. The peaks were assigned to dipole oscillation excitations. These peak energies almost coincided with the peak energy of optical absorption of a heat-shielding filter with LaB 6 nanoparticles. On the other hand, those energies were a smaller than a dipole oscillation energy predicted using the dielectric function of bulk LaB 6 crystal. It is suggested that the lower energy than expected is due to an excitation at 1.2 eV, which was observed for oxidized LaB 6 area. -- Highlights: → The dielectric properties of LaB 6 nanoparticles applied to solar heat-shielding filters were studied by HR-EELS. → Plasmon peak energies of the LaB 6 nanoparticles were almost equal to optical absorption energy of a heat-shielding filter. → From this result, near-infrared optical absorption of the filter is due to the surface dipole mode of the nanoparticles.

Nuclear matter with pseudo-particle model: static bulk and surface properties

Energy Technology Data Exchange (ETDEWEB)

Idier, D.; Benhassine, B.; Farine, M.; Remaud, B.; Sebille, F.

1993-12-31

Direct calculations of cold and hot nuclear matter (bulk and surface properties) are carried out within the frame of a pseudo-particle model using a Gaussian decomposition of the distribution function. Comparisons with Hartree-Fock calculations, for a large class of effective interactions, show that such a model is reliable to reproduce accurately the equation of state of nuclear matter for large ranges of densities and temperatures. The number of Gaussian per nucleon and the Gaussian widths are critical parameters in that semi-classical model. (author) 13 refs.; 9 figs.; 2 tabs.

Nuclear matter with pseudo-particle model: static bulk and surface properties

International Nuclear Information System (INIS)

Idier, D.; Benhassine, B.; Farine, M.; Remaud, B.; Sebille, F.

1993-01-01

Direct calculations of cold and hot nuclear matter (bulk and surface properties) are carried out within the frame of a pseudo-particle model using a Gaussian decomposition of the distribution function. Comparisons with Hartree-Fock calculations, for a large class of effective interactions, show that such a model is reliable to reproduce accurately the equation of state of nuclear matter for large ranges of densities and temperatures. The number of Gaussian per nucleon and the Gaussian widths are critical parameters in that semi-classical model. (author) 13 refs.; 9 figs.; 2 tabs

Observation and analysis of water inherent optical properties

Science.gov (United States)

Sun, Deyong; Li, Yunmei; Le, Chengfeng; Huang, Changchun

2008-03-01

Inherent optical property is an important part of water optical properties, and is the foundation of water color analytical model establishment. Through quantity filter technology (QFT) and backscattering meter BB9 (WETlabs Inc), absorption coefficients of CDOM, total suspended minerals and backscattering coefficients of total suspended minerals had been observed in Meiliang Bay of Taihu lake at summer and winter respectively. After analyzing the spectral characteristics of absorption and backscattering coefficients, the differences between two seasons had been illustrated adequately, and the reasons for the phenomena, which are related to the changes of water quality coefficient, had also been explained. So water environment states can be reflected by inherent optical properties. In addition, the relationship models between backscattering coefficients and suspended particle concentrations had been established, which can support coefficients for analytical models.

Optical modelling data for room temperature optical properties of organic–inorganic lead halide perovskites

Directory of Open Access Journals (Sweden)

Yajie Jiang

2015-06-01

Full Text Available The optical properties of perovskites at ambient temperatures are important both to the design of optimised solar cells as well as in other areas such as the refinement of electronic band structure calculations. Limited previous information on the optical modelling has been published. The experimental fitting parameters for optical constants of CH3NH3PbI3−xClx and CH3NH3PbI3 perovskite films are reported at 297 K as determined by detailed analysis of reflectance and transmittance data. The data in this study is related to the research article “Room temperature optical properties of organic–inorganic lead halide perovskites” in Solar Energy Materials & Solar Cells [1].

High mechanical Q-factor measurements on silicon bulk material

Energy Technology Data Exchange (ETDEWEB)

Schwarz, Christian; Nawrodt, Ronny; Heinert, Daniel; Schroeter, Anja; Neubert, Ralf; Thuerk, Matthias; Vodel, Wolfgang; Seidel, Paul [Institut fuer Festkoerperphysik, Helmholtzweg 5, D-07743 Jena (Germany); Tuennermann, Andreas [Institut fuer Angewandte Physik, Albert-Einstein-Strasse 15, D-07745 Jena (Germany)

2008-07-01

The direct observation of gravitational waves is one of the biggest challenges in science. Current detectors are limited by different kinds of noise. One of the fundamental noise sources is thermal noise arising from the optical components. One of the most promising attempts to reduce the thermal noise contribution in future detectors will be the use of high Q-factor materials at cryogenic temperatures. Silicon seems to be the most interesting material due to its excellent optical and thermal properties. We present high Q-factor measurements on bulk samples of high purity silicon in a temperature range from 5 to 300 K. The sample dimensions vary between 76.2 mm x 12..75 mm. The Q-factor exceeds 4.10{sup 8} at 6 K. The influence of the crystal orientation, doping and the sample preparation on the Q-factor is discussed.

Effect of neutron irradiation on etching, optical and structural properties of microscopic glass slide used as a solid state nuclear track detector

International Nuclear Information System (INIS)

Singh, Surinder; Kaur Sandhu, Amanpreet; Prasher, Sangeeta; Prakash Pandey, Om

2007-01-01

Microscopic glass slides are soda-lime glasses which are readily available and are easy to manufacture with low production cost. The application of these glasses as nuclear track detector will help us to make use of these glasses as solid-state nuclear track detector. The present paper describes the variation in the etching, optical and structural properties of the soda-lime microscopic glass slides due to neutron irradiation of different fluences. The color transformation and an increase in the optical absorption with neutron irradiation are observed. Both the bulk and track etch rates are found to increase with neutron fluence, thus showing a similar dependence on neutron fluence, but the sensitivity remains almost constant

The role of cationic precursors in structural, morphological and optical properties of PbS thin films

International Nuclear Information System (INIS)

Preetha, K C; Murali, K V; Ragina, A J; Deepa, K; Dhanya, A C; Remadevi, T L

2013-01-01

Thin films of Lead sulphide (PbS) were grown on soda lime glass substrate by Successive Ionic Layer Adsorption and Reaction (SILAR) method using lead acetate, lead chloride, lead nitrate, and lead sulphate as cationic precursors and thioacetamide as sulphur source. The experiments were carried out at room temperature under normal pressure utilizing aqueous conditions. The structural and morphological aspects of the as prepared samples were investigated by means of XRD and SEM results. The prepared samples were polycrystalline with nanometer-sized grains and identified as galena type cubic structure (FCC). The values of average crystallite size were found to be in the range 22 to 30 nm. The SEM micrographs show variations in morphology. Optical studies revealed that the absorption edges of the films indicated strong blue shifts with respect to bulk sample. In this work, we establish that the cationic precursor sources and in turn the size of the crystallites affects the structural, morphological and optical properties of PbS thin films.

Maritime Aerosol optical properties measured by ship-borne sky radiometer

Science.gov (United States)

Aoki, K.

2017-12-01

Maritime aerosols play an important role in the earth climate change. We started the measurements of aerosol optical properties since 1994 by using ship-borne sky radiometer (POM-01 MK-II and III; Prede Co. Ltd., Japan) over the ocean. We report the results of an aerosol optical properties over the ocean by using Research Vessel of the ship-borne sky radiometers. Aerosol optical properties observation were made in MR10-02 to MR16-09 onboard the R/V Mirai, JAMSTEC. The sky radiometer measure the direct and diffuse solar radiance with seven interference filters (0.315, 0.4, 0.5, 0.675, 0.87, 0.94, and 1.02 µm). Observation interval was made every five minutes by once, only in daytime under the clear sky conditions. GPS provides the position with longitude and latitude and heading direction of the vessel, and azimuth and elevation angle of the sun. The aerosol optical properties were computed using the SKYRAD.pack version 4.2. The obtained Aerosol optical properties (Aerosol optical thickness, Ångström exponent, Single scattering albedo, and etc.) and size distribution volume clearly showed spatial and temporal variability over the ocean. Aerosol optical thickness found over the near the coast (Asia and Tropical area) was high and variable. The size distribution volume have peaks at small particles at Asian coast and large particles at Tropical coast area. We provide the information, in this presentation, on the aerosol optical properties measurements with temporal and spatial variability in the Maritime Aerosol. This project is validation satellite of GCOM-C/SGLI, JAXA and other. The GCOM-C satellite scheduled to be launched in 2017 JFY.

Electronic and optical properties of lead iodide

DEFF Research Database (Denmark)

Ahuja, R.; Arwin, H.; Ferreira da Silva, A.

2002-01-01

The electronic properties and the optical absorption of lead iodide (PbI2) have been investigated experimentally by means of optical absorption and spectroscopic ellipsometry, and theoretically by a full-potential linear muffin-tin-orbital method. PbI2 has been recognized as a very promising...

Optical properties on thermally evaporated and heat-treated ...

Indian Academy of Sciences (India)

Administrator

of the intra-molecular bonds between the powder compounds and thin films. The optical ... Keywords. Phthalocyanine; thin films; optical properties; absorption spectra. 1. .... Leica Cambridge scanning electron microscope (model. Stereoscan ...

Growth of Bulk Wide Bandgap Semiconductor Crystals and Their Potential Applications

Science.gov (United States)

Chen, Kuo-Tong; Shi, Detang; Morgan, S. H.; Collins, W. Eugene; Burger, Arnold

1997-01-01

Developments in bulk crystal growth research for electro-optical devices in the Center for Photonic Materials and Devices since its establishment have been reviewed. Purification processes and single crystal growth systems employing physical vapor transport and Bridgman methods were assembled and used to produce high purity and superior quality wide bandgap materials such as heavy metal halides and II-VI compound semiconductors. Comprehensive material characterization techniques have been employed to reveal the optical, electrical and thermodynamic properties of crystals, and the results were used to establish improved material processing procedures. Postgrowth treatments such as passivation, oxidation, chemical etching and metal contacting during the X-ray and gamma-ray device fabrication process have also been investigated and low noise threshold with improved energy resolution has been achieved.

First principles study of the electronic and optical properties of GaAs nanoparticles under the influence of external uniform electric field

International Nuclear Information System (INIS)

Bezi Javan, Masoud

2012-01-01

We present electronic and optical properties of the hydrogen terminated gallium arsenide nanoparticles using time dependent density functional theory (TD-DFT). The electronic and optical properties of the GaAs nanoparticles were calculated at presence of the uniform external electric field in the range from 0 to 0.51 V/Å. The induced electric filed can decrease the HOMO–LUMO gap of the nanoparticles and the mount of these reductions increases with gain of the electric field strength. -- Highlights: ► HOMO–LUMO gap of the nanoparticles is significantly more than GaAs bulk band gap. ► HOMO–LUMO gap of the nanoparticles decreases with increase of the nanoparticles size. ► External electric filed decrease the HOMO–LUMO gap of the nanoparticles. ► Dipole moment of nanoparticles increases with gain of the electric field strength. ► Absorption peaks of GaAs nanoparticles shows red shift with applying electric field.

Polymerization Behavior and Mechanical Properties of High-Viscosity Bulk Fill and Low Shrinkage Resin Composites.

Science.gov (United States)

Shibasaki, S; Takamizawa, T; Nojiri, K; Imai, A; Tsujimoto, A; Endo, H; Suzuki, S; Suda, S; Barkmeier, W W; Latta, M A; Miyazaki, M

The present study determined the mechanical properties and volumetric polymerization shrinkage of different categories of resin composite. Three high viscosity bulk fill resin composites were tested: Tetric EvoCeram Bulk Fill (TB, Ivoclar Vivadent), Filtek Bulk Fill posterior restorative (FB, 3M ESPE), and Sonic Fill (SF, Kerr Corp). Two low-shrinkage resin composites, Kalore (KL, GC Corp) and Filtek LS Posterior (LS, 3M ESPE), were used. Three conventional resin composites, Herculite Ultra (HU, Kerr Corp), Estelite ∑ Quick (EQ, Tokuyama Dental), and Filtek Supreme Ultra (SU, 3M ESPE), were used as comparison materials. Following ISO Specification 4049, six specimens for each resin composite were used to determine flexural strength, elastic modulus, and resilience. Volumetric polymerization shrinkage was determined using a water-filled dilatometer. Data were evaluated using analysis of variance followed by Tukey's honestly significant difference test (α=0.05). The flexural strength of the resin composites ranged from 115.4 to 148.1 MPa, the elastic modulus ranged from 5.6 to 13.4 GPa, and the resilience ranged from 0.70 to 1.0 MJ/m 3 . There were significant differences in flexural properties between the materials but no clear outliers. Volumetric changes as a function of time over a duration of 180 seconds depended on the type of resin composite. However, for all the resin composites, apart from LS, volumetric shrinkage began soon after the start of light irradiation, and a rapid decrease in volume during light irradiation followed by a slower decrease was observed. The low shrinkage resin composites KL and LS showed significantly lower volumetric shrinkage than the other tested materials at the measuring point of 180 seconds. In contrast, the three bulk fill resin composites showed higher volumetric change than the other resin composites. The findings from this study provide clinicians with valuable information regarding the mechanical properties and

The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

International Nuclear Information System (INIS)

Kim, S.B.; Uwani, Y.; Joo, J.H.; Kawamoto, R.; Jo, Y.S.

2011-01-01

The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HTS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HTS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets.

Human tissue optical properties measurements and light propagation modelling

CSIR Research Space (South Africa)

Dam, JS

2006-07-01

Full Text Available Biomedical Optics is the study of the optical properties of living biological material, especially its scattering and absorption characteristics, and their significance to light propagation within the material. Determination of tissue optical...

The CLASS blazar survey - II. Optical properties

NARCIS (Netherlands)

Caccianiga, A; Marcha, MJ; Anton, S; Mack, KH; Neeser, MJ

2002-01-01

This paper presents the optical properties of the objects selected in the CLASS blazar survey. Because an optical spectrum is now available for 70 per cent of the 325 sources present in the sample, a spectral classification, based on the appearance of the emission/absorption lines, is possible. A

Flux pinning properties of impurity doped MgB2 bulks synthesized by diffusion method

International Nuclear Information System (INIS)

Ueda, Shinya; Shimoyama, Jun-ichi; Yamamoto, Akiyasu; Katsura, Yukari; Iwayama, Isao; Horii, Shigeru; Kishio, Kohji

2005-01-01

Doping effects of carbon-containing impurities on the critical current properties and microstructure were systematically studied for highly dense MgB 2 bulks prepared by the diffusion method starting from magnesium and boron which are separately packed in sealed stainless tubes. Obtained samples exhibited improved critical current density, J c , simply by an increase of effective current pass. A non-doped MgB 2 recorded almost double high J c at 20 K compared with those of the conventional porous MgB 2 bulks having ∼50% of the theoretical density, while irreversibility field, H irr , did not largely change. J c under high magnetic fields were enhanced by doping of carbon-containing impurities, such as SiC and B 4 C. Optimal doping levels of SiC and B 4 C for high critical current properties at 20 K are found to be ∼2% and 5%, respectively, as nominal carbon concentration at boron site. Difference in the optimal doping levels is originated from the difference in their reactivity

First–principle calculation of the elastic, band structure, electronic states, and optical properties of Cu–doped ZnS nanolayers

Energy Technology Data Exchange (ETDEWEB)

Lahiji, Mohammadreza Askaripour, E-mail: m.a.lahijiii@gmail.com [Department of applied mathematics, Astaneh Ashrafieh Branch, Islamic Azad University, Astaneh Ashrafieh (Iran, Islamic Republic of); Ziabari, Ali Abdolahzadeh, E-mail: ali.abd.ziabari@gmail.com [Nano Research Lab, Lahijan Branch, Islamic Azad University, P.O. Box: 1616, Lahijan (Iran, Islamic Republic of)

2016-11-15

The structural, elastic, electronic, and optical properties of undoped and Cu–doped ZnS nanostructured layers have been studied in the zincblende (ZB) phase, by first–principle approach. Density functional theory (DFT) has been employed to calculate the fundamental properties of the layers using full–potential linearized augmented plane–wave (FPLAPW) method. Mechanical analysis revealed that the bulk modulus increases with the increase of Cu content. Cu doping was found to reduce the band gap value of the material. In addition, DOS effective mass of the electrons and heavy holes was evaluated. Adding Cu caused the decrement/increment of transmission/reflectance of nanolayers in the UV–vis region. The substitution by Cu increased the intensity of the peaks, and a slight red shift was observed in the absorption peak. Moreover, the static dielectric constant, and static refractive index increased with Cu content. The optical conductivity also followed a similar trend to that of the dielectric constants. Energy loss function of the modeled compounds was also evaluated. All calculated parameters were compared with the available experimental and other theoretical results.

A first principle Comparative study of electronic and optical properties of 1H –MoS2 and 2H –MoS2

International Nuclear Information System (INIS)

Kumar, Ashok; Ahluwalia, P.K.

2012-01-01

First principle calculations of electronic and optical properties of monolayer MoS 2 , so called 1H –MoS 2 , is performed which has emerged as a new direct band gap semiconductor. Before calculations of the properties of 1H –MoS 2 , we have calculated structural parameters, electronic properties (electronic band structure and electronic density of states) and frequency dependent optical response (real and imaginary part of dielectric function, energy loss function, absorption and reflectance spectra) of 2H –MoS 2 and compared with existing experimental results and found that our calculated results are in very good agreements with experimental results. To compare the dielectric functions of bulk (2H –MoS 2 ) and monolayer (1H –MoS 2 ) phases we have further extended these calculations to the single layer MoS 2 (1H –MoS 2 ) which is analogous to graphene. Structural parameters of 1H –MoS 2 are found very close to its bulk 2H –MoS 2 . We find direct electronic band gap at ‘K’ high symmetry point as compared to indirect band gap in its bulk 2H – MoS2. Our calculated dielectric function for 1H – MoS2 shows structure at nearly same energy positions as compared to 2H – MoS2 with additional structure at 3.8 eV. Also additional well defined energy loss peaks revealing the plasmonic resonances at 15.7 eV and 16.0 eV for E vector perpendicular and parallel to c axis respectively for 1H – MoS2 have been found, which are the signatures of surface plasmons at these energies. -- Highlights: ► Structural parameters of 2H-MoS2 and 1H-MoS2 are nearly identical. ► States around the Fermi energy are mainly due to the metal d states. ► Strong hybridization between Mo-d and S-p states below the Fermi energy has been found. ► Optical spectra of 2H-MoS2 finds very good agreements with experimental optical spectra. ► The band gap is found to be direct for 1H-MoS2 as compared to indirect for 2H-MoS2.

Quantitative analysis of reflection electron energy loss spectra to determine electronic and optical properties of Fe–Ni alloy thin films

International Nuclear Information System (INIS)

Tahir, Dahlang; Oh, Sukh Kun; Kang, Hee Jae; Tougaard, Sven

2016-01-01

Highlights: • Electronic and optical properties of Fe-Ni alloy thin films grown on Si (1 0 0) were studied via quantitative analyses of reflection electron energy loss spectra (REELS). • The energy loss functions (ELF) are dominated by a plasmon peak at 23.6 eV for Fe and moves gradually to lower energies in Fe-Ni alloys towards the bulk plasmon energy of Ni at 20.5 eV. • Fe has a strong effect on the dielectric and optical properties of Fe-Ni alloy thin films even for an alloy with 72% Ni. Electronic and optical properties of Fe-Ni alloy thin films grown on Si (1 0 0) were studied via quantitative analyses of reflection electron energy loss spectra (REELS). - Abstract: Electronic and optical properties of Fe–Ni alloy thin films grown on Si (1 0 0) by ion beam sputter deposition were studied via quantitative analyses of reflection electron energy loss spectra (REELS). The analysis was carried out by using the QUASES-XS-REELS and QUEELS-ε(k,ω)-REELS softwares to determine the energy loss function (ELF) and the dielectric functions and optical properties by analyzing the experimental spectra. For Ni, the ELF shows peaks around 3.6, 7.5, 11.7, 20.5, 27.5, 67 and 78 eV. The peak positions of the ELF for Fe_2_8Ni_7_2 are similar to those of Fe_5_1Ni_4_9, even though there is a small peak shift from 18.5 eV for Fe_5_1Ni_4_9 to 18.7 eV for Fe_2_8Ni_7_2. A plot of n, k, ε_1, and ε_2 shows that the QUEELS-ε(k,ω)-REELS software for analysis of REELS spectra is useful for the study of optical properties of transition metal alloys. For Fe–Ni alloy with high Ni concentration (Fe_2_8Ni_7_2), ε_1, and ε_2 have strong similarities with those of Fe. This indicates that the presence of Fe in the Fe–Ni alloy thin films has a strong effect.

Characterization of black and white chromium electrodeposition films. Surface and optical properties

Energy Technology Data Exchange (ETDEWEB)

Aguilar, M.; Palomar-Pardave, M. [Departamento de Materiales, UAM-Azcapotzalco, Av. San Pablo No. 180, Col. Reynosa Tamaulipas, Mexico D.F. 02200 (Mexico); Barrera, E. [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana - Iztapalapa, Av. Rafael Atlixco No. 186, Col. Vicentina, Mexico, D.F. 09340 (Mexico); Huerta, L.; Muhl, S. [Instituto de Investigaciones en Materiales, UNAM, Mexico, D.F. 04510 (Mexico)

2003-11-01

Thin films of black and white chromium have been prepared by electrodeposition on stainless steel substrates. The potentiodynamic and potentiostatic technique was used in order to prepare these materials. XRD, XPS, SEM and spectral reflectance in the UV-Visible-near IR and medium IR ranges, for both films coatings were characterized. From the SEM analysis, it was found while the black chromium has a lamellar morphology that leads to a strong dispersion level, the white one has a flat morphology. The chemical composition of these thin films was determined by XRD and XPS technique. The XRD results showed that in both cases chromium is the main bulk chemical compound in both films. However, from XPS analysis of these surfaces, it was possible to determine that the most external layers of the films are made of different kinds of chromium compounds. The black chromium film has better optical properties to transform solar energy into thermal energy, and these properties remain practically constant even when heat treated to a high temperature, 400 C. On the other hand the white chromium film is a better substrate for hydrogen evolution reactions than the black one.

Electronic, Optical, and Thermal Properties of Reduced-Dimensional Semiconductors

Science.gov (United States)

Huang, Shouting

Reduced-dimensional materials have attracted tremendous attention because of their new physics and exotic properties, which are of great interests for fundamental science. More importantly, the manipulation and engineering of matter on an atomic scale yield promising applications for many fields including nanoelectronics, nanobiotechnology, environments, and renewable energy. Because of the unusual quantum confinement and enhanced surface effect of reduced-dimensional materials, traditional empirical models suffer from necessary but unreliable parameters extracted from previously-studied bulk materials. In this sense, quantitative, parameter-free approaches are highly useful for understanding properties of reduced-dimensional materials and, furthermore, predicting their novel applications. The first-principles density functional theory (DFT) is proven to be a reliable and convenient tool. In particular, recent progress in many-body perturbation theory (MBPT) makes it possible to calculate excited-state properties, e.g., quasiparticle (QP) band gap and optical excitations, by the first-principles approach based on DFT. Therefore, during my PhD study, I employed first-principles calculations based on DFT and MBPT to systematically study fundamental properties of typical reduced-dimensional semiconductors, i.e., the electronic structure, phonons, and optical excitations of core-shell nanowires (NWs) and graphene-like two-dimensional (2D) structures of current interests. First, I present first-principles studies on how to engineer band alignments of nano-sized radial heterojunctions, Si/Ge core-shell NWs. Our calculation reveals that band offsets in these one-dimensional (1D) nanostructures can be tailored by applying axial strain or varying core-shell sizes. In particular, the valence band offset can be efficiently tuned across a wide range and even be diminished via applied strain. Two mechanisms contribute to this tuning of band offsets. Furthermore, varying the

Cloud-Driven Changes in Aerosol Optical Properties - Final Technical Report

Energy Technology Data Exchange (ETDEWEB)

Ogren, John A.; Sheridan, Patrick S.; Andrews, Elisabeth

2007-09-30

The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles’ lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.

Optical properties of amorphous silicon: Some problem areas

International Nuclear Information System (INIS)

Ravindra, N.M.; Chelle, F. de; Ance, C.; Ferraton, J.P.; Berger, J.M.; Coulibaly, S.P.

1983-08-01

In this presentation we essentially attempt to throw light on some problem areas concerning the various optical properties of amorphous silicon. The problems seem to emerge from the classical methods employed to determine the optical properties like the optical gap, urbach tail parameter and other related characteristics. Additional problems have emerged in recent years by virtue of many attempts to generalize the property-behaviour relationships for amorphous silicon without attributing any importance to the method of preparation of the films. It should be noted here that although many authors believe disorder to be the controlling parameter, we are of the opinion that at least for films containing fairly large concentrations of hydrogen, the hydrogen concentration has an equally important role to play. The present study has been carried out for films prepared by glow-discharge and chemical vapour deposition. (author)

Temperature dependence of PZT film optical properties

Czech Academy of Sciences Publication Activity Database

Deineka, Alexander; Jastrabík, Lubomír; Suchaneck, G.; Gerlach, G.

11-12, - (2001), s. 352-354 ISSN 0447-6441 R&D Projects: GA ČR GA202/00/1425; GA MŠk LN00A015 Institutional research plan: CEZ:AV0Z1010914 Keywords : refractive index profile * PZT film * temperature dependence of optical properties Subject RIV: BH - Optics, Masers, Lasers

Handbook of the Properties of Optical Materials

Science.gov (United States)

1984-01-01

EFFECTIVE MASS - - MOBILITY - - A-2 ARSEWIC SELENIOE (As2 Se3 ) OPTICAL PROPERTIES TRANSMISSION RANGE: 9 - 11n Optical Absorption Coefficient = 0.079...of 55 KRS-5 as a function of wavelength. A-2120 ZINC SELENIOE ZnSe 0 STRUCTURE CRYSTALLINE SYMMETRY = Cubic, 43m LATTICE CONSTANTS (A) = a = 5.667

Theoretical Studies of Optical Properties of Silver Nanoparticles

International Nuclear Information System (INIS)

Ye-Wan, Ma; Zhao-Wang, Wu; Li-Hua, Zhang; Jie, Zhang

2010-01-01

Optical properties of silver nanoparticles such as extinction, absorption and scattering efficiencies are studied based on Green's function theory. The numerical simulation results show that optical properties of silver nanoparticles are mainly dependent on their sizes and geometries; the localized plasmon resonance peak is red shifted when the dielectric constant of the particle's surrounding medium increases or when a substrate is presented. The influences of wave polarizations, the incident angles of light, the composite silver and multiply-layers on the plasmon resonance are also reported. The numerical simulation of optical spectra is a very useful tool for nanoparticle growth and characterization. (fundamental areas of phenomenology(including applications))

Inhomogeneous electron distribution in InN nanowires: Influence on the optical properties

Energy Technology Data Exchange (ETDEWEB)

Molina-Sanchez, A.; Garro, N.; Garcia-Cristobal, A.; Cantarero, A. [Instituto de Ciencia de los Materiales, Universidad de Valencia (Spain); Segura-Ruiz, J. [European Synchrotron Radiation Facility, Experiments Div., Grenoble (France); Iikawa, F. [Instituto de Fisica Gleb Wataghin - Unicamp, CP 6165, Campinas (Brazil); Denker, C.; Malindretos, J.; Rizzi, A. [IV. Physikalisches Institut, Georg-August Universitaet Goettingen (Germany)

2012-03-15

In this work, we study theoretically and experimentally the influence of the surface electron accumulation on the optical properties of InN nanowires. For this purpose, the photoluminescence and photoluminescence excitation spectra have been measured for a set of self-assembled InN NWs grown under different conditions. The photoluminescence excitation experimental lineshapes have been reproduced by a self-consistent calculation of the absorption in a cylindrical InN nanowires. With the self-consistent model we can explore how the optical absorption depends on nanowires radius and doping concentration. Our model solves the Schroedinger equation for a cylindrical nanowire of infinite length, assuming a parabolic conduction band. The columnar geometry introduces effects in both the electron density and in the self-consistent conduction band profile, with no equivalence in planar layer. On the other hand, the differences in the photoluminescence excitation spectra are related to the inhomogeneous electron distribution inside the nanowires, caused by a bulk donor concentration and a two-dimensional density of ionized surface states. For nanowire radii larger than 30 nm, such concentrations modify the absorption edge and the lineshape, respectively, and can be determined from the comparison with the experimental data (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Characterizing the optical properties of human brain tissue with high numerical aperture optical coherence tomography.

Science.gov (United States)

Wang, Hui; Magnain, Caroline; Sakadžić, Sava; Fischl, Bruce; Boas, David A

2017-12-01

Quantification of tissue optical properties with optical coherence tomography (OCT) has proven to be useful in evaluating structural characteristics and pathological changes. Previous studies primarily used an exponential model to analyze low numerical aperture (NA) OCT measurements and obtain the total attenuation coefficient for biological tissue. In this study, we develop a systematic method that includes the confocal parameter for modeling the depth profiles of high NA OCT, when the confocal parameter cannot be ignored. This approach enables us to quantify tissue optical properties with higher lateral resolution. The model parameter predictions for the scattering coefficients were tested with calibrated microsphere phantoms. The application of the model to human brain tissue demonstrates that the scattering and back-scattering coefficients each provide unique information, allowing us to differentially identify laminar structures in primary visual cortex and distinguish various nuclei in the midbrain. The combination of the two optical properties greatly enhances the power of OCT to distinguish intricate structures in the human brain beyond what is achievable with measured OCT intensity information alone, and therefore has the potential to enable objective evaluation of normal brain structure as well as pathological conditions in brain diseases. These results represent a promising step for enabling the quantification of tissue optical properties from high NA OCT.

Quantum dot devices for optical communications

DEFF Research Database (Denmark)

Mørk, Jesper

2005-01-01

-low threshold currents and amplifiers with record-high power levels. In this tutorial we will review the basic properties of quantum dots, emphasizing the properties which are important for laser and amplifier applications, as well as devices for all-optical signal processing. The high-speed properties....... The main property of semiconductor quantum dots compared to bulk material or even quantum well structures is the discrete nature of the allowed states, which means that inversion of the medium can be obtained for very low electron densities. This has led to the fabrication of quantum dot lasers with record...

Optical limiting properties of fullerenes and related materials

Science.gov (United States)

Riggs, Jason Eric

Optical limiting properties of fullerene C60 and different C60 derivatives (methano-, pyrrolidino-, and amino-) towards nanosecond laser pulses at 532 nm were studied. The results show that optical limiting responses of the C60 derivatives are similar to those of the parent C60 despite their different linear absorption and emission properties. For C60 and the derivatives in room-temperature solutions of varying concentrations and optical path length, the optical limiting responses are strongly concentration dependent. The concentration dependence is not due to any optical artifacts since the results obtained under the same experimental conditions for reference systems show no such dependence. Similarly, optical limiting results of fullerenes are strongly dependent on the medium viscosity, with responses in viscous media weaker than that in room-temperature solutions. The solution concentration and medium viscosity dependencies are not limited to fullerenes. In fact, the results from a systematic investigation of several classes of nonlinear absorptive organic dyes show that the optical limiting responses are also concentration and medium viscosity dependent. Interestingly, however, such dependencies are uniquely absent in the optical limiting responses of metallophthalocyanines. In classical photophysics, the strong solution concentration and medium viscosity dependencies are indicative of significant contributions from photoexcited-state bimolecular processes. Thus, the experimental results are discussed in terms of a significantly modified five-level reverse saturable absorption mechanism. Optical limiting properties of single-walled and multiple-walled carbon nanotubes toward nanosecond laser pulses at 532 nm were also investigated. When suspended in water, the single-walled and multiple-walled carbon nanotubes exhibit essentially the same optical limiting responses, and the results are also comparable with those of carbon black aqueous suspension. For

Structural and optical properties of Si-doped Ag clusters

KAUST Repository

Mokkath, Junais Habeeb

2014-03-06

The structural and optical properties of AgN and Ag N-1Si1 (neutral, cationic, and anionic) clusters (N = 5 to 12) are systematically investigated using the density functional based tight binding method and time-dependent density functional theory, providing insight into recent experiments. The gap between the highest occupied and lowest unoccupied molecular orbitals and therefore the optical spectrum vary significantly under Si doping, which enables flexible tuning of the chemical and optical properties of Ag clusters. © 2014 American Chemical Society.

Structural and optical properties of Si-doped Ag clusters

KAUST Repository

Mokkath, Junais Habeeb; Schwingenschlö gl, Udo

2014-01-01

The structural and optical properties of AgN and Ag N-1Si1 (neutral, cationic, and anionic) clusters (N = 5 to 12) are systematically investigated using the density functional based tight binding method and time-dependent density functional theory, providing insight into recent experiments. The gap between the highest occupied and lowest unoccupied molecular orbitals and therefore the optical spectrum vary significantly under Si doping, which enables flexible tuning of the chemical and optical properties of Ag clusters. © 2014 American Chemical Society.

Influence of various irradiation processes on the mechanical properties and polymerisation kinetics of bulk-fill resin based composites.

Science.gov (United States)

Ilie, Nicoleta; Keßler, Andreas; Durner, Jürgen

2013-08-01

To assess the effect of irradiation time and distance of the light tip on the micro-mechanical properties and polymerisation kinetics of two bulk-fill resin-based composites at simulated clinically relevant filling depth. Micro-mechanical properties (Vickers hardness (HV), depth of cure (DOC) and indentation modulus (E)) and polymerisation kinetics (real-time increase of degree of cure (DC)) of two bulk-fill resin-based composites (Tetric EvoCeram(®) Bulk Fill, Ivoclar Vivadent and x-tra base, Voco) were assessed at varying depth (0.1-6mm in 100μm steps for E and HV and 0.1, 2, 4 and 6mm for DC), irradiation time (10, 20 or 40s, Elipar Freelight2) and distances from the light tip (0 and 7mm). Curing unit's irradiance was monitored in 1mm steps at distances up to 10mm away from the light tip on a laboratory-grade spectrometer. Multivariate analysis (α=0.05), Student's t-test and Pearson correlation analysis were considered. The influence of material on the measured mechanical properties was significant (η(2)=0.080 for E and 0.256 for HV), while the parameters irradiation time, distance from the light tip and depth emphasise a stronger influence on Tetric EvoCeram(®) Bulk Fill. The polymerisation kinetics could be described by an exponential sum function, distinguishing between the gel and the glass phase. The above mentioned parameters strongly influenced the start of polymerisation (gel phase), and were of less importance for the glass phase. Both materials enable at least 4mm thick increments to be cured in one step under clinically relevant curing conditions. The susceptibility to variation in irradiance was material dependent, thus properties measured under clinically simulated curing conditions might vary to a different extent from those measured under ideal curing conditions. Copyright © 2013 Elsevier Ltd. All rights reserved.

Multifragmentation of a very heavy nuclear system (II): bulk properties and spinodal decomposition

Energy Technology Data Exchange (ETDEWEB)

Frankland, J.D.; Rivet, M.F.; Borderie, B. [Paris-11 Univ., Inst. de Physique Nucleaire, 91 - Orsay (France)] [and others

2000-07-01

The properties of fragments and light charged particles emitted in multifragmentation of single sources formed in central 36 A.MeV Gd+U collisions are reviewed. Most of the products are isotropically distributed in the reaction c.m. Fragment kinetic energies reveal the onset of radial collective energy. A bulk effect is experimentally evidenced from the similarity of the charge distribution with that from the lighter 32 A.MeV Xe+Sn system. Spinodal decomposition of finite nuclear matter exhibits the same property in simulated central collisions for the two systems, and appears therefore as a possible mechanism at the origin of multifragmentation in this incident energy domain. (authors)

Multifragmentation of a very heavy nuclear system (II): bulk properties and spinodal decomposition

International Nuclear Information System (INIS)

Frankland, J.D.; Rivet, M.F.; Borderie, B.

2000-01-01

The properties of fragments and light charged particles emitted in multifragmentation of single sources formed in central 36 A.MeV Gd+U collisions are reviewed. Most of the products are isotropically distributed in the reaction c.m. Fragment kinetic energies reveal the onset of radial collective energy. A bulk effect is experimentally evidenced from the similarity of the charge distribution with that from the lighter 32 A.MeV Xe+Sn system. Spinodal decomposition of finite nuclear matter exhibits the same property in simulated central collisions for the two systems, and appears therefore as a possible mechanism at the origin of multifragmentation in this incident energy domain. (authors)

Mechanical properties of nano and bulk Fe pillars using molecular dynamics and dislocation dynamics simulation

Directory of Open Access Journals (Sweden)

S. K. Deb Nath

2017-10-01

Full Text Available Using molecular dynamics simulation, tension and bending tests of a Fe nanopillar are carried out to obtain its Young’s modulus and yield strength. Then the comparative study of Young’s modulus and yield strength of a Fe nanopillar under bending and tension are carried out varying its diameter in the range of diameter 1-15nm. We find out the reasons why bending Young’s modulus and yield strength of a Fe nanopillar are higher than those of tension Young’s modulus and yield strength of a Fe nanopillar. Using the mobility parameters of bulk Fe from the experimental study [N. Urabe and J. Weertman, Materials Science and Engineering 18, 41 (1975], its temperature dependent stress-strain relationship, yield strength and strain hardening modulus are obtained from the dislocation dynamics simulations. Strain rate dependent yield strength and strain hardening modulus of bulk Fe pillars under tension are studied. Temperature dependent creep behaviors of bulk Fe pillars under tension are also studied. To verify the soundness of the present dislocation dynamics studies of the mechanical properties of bulk Fe pillars under tension, the stress vs. strain relationship and dislocation density vs. strain of bulk Fe pillars obtained by us are compared with the published results obtained by S. Queyreau, G. Monnet, and B. Devincre, International Journal of Plasticity 25, 361 (2009.

Structural, optical and electrical properties of chemically deposited ...

Indian Academy of Sciences (India)

Structural, optical and electrical properties of chemically deposited nonstoichiometric copper ... One of these compounds, CuInSe2, with its optical absorption .... is clear from SEM images that the number of grains goes on increasing with the ...

Optical properties of GaAs

International Nuclear Information System (INIS)

Akinlami, J. O.; Ashamu, A. O.

2013-01-01

We have investigated the optical properties of gallium arsenide (GaAs) in the photon energy range 0.6–6.0 eV. We obtained a refractive index which has a maximum value of 5.0 at a photon energy of 3.1 eV; an extinction coefficient which has a maximum value of 4.2 at a photon energy of 5.0 eV; the dielectric constant, the real part of the complex dielectric constant has a maximum value of 24 at a photon energy of 2.8 eV and the imaginary part of the complex dielectric constant has a maximum value of 26.0 at a photon energy of 4.8 eV; the transmittance which has a maximum value of 0.22 at a photon energy of 4.0 eV; the absorption coefficient which has a maximum value of 0.22 × 10 8 m −1 at a photon energy of 4.8 eV, the reflectance which has a maximum value of 0.68 at 5.2eV; the reflection coefficient which has a maximum value of 0.82 at a photon energy of 5.2 eV; the real part of optical conductivity has a maximum value of 14.2 × 10 15 at 4.8 eV and the imaginary part of the optical conductivity has a maximum value of 6.8 × 10 15 at 5.0 eV. The values obtained for the optical properties of GaAs are in good agreement with other results. (semiconductor physics)

Assessing the dependence of bulk ice properties from probes with anti-shatter tips on environmental conditions

Science.gov (United States)

Jackson, Robert C.

Ice clouds have significant impacts on the Earth's radiative budget. Their radiative impact highly depends on ice cloud microphysical properties. Climate and weather prediction models have to make certain assumptions about how the various processes are represented. Observations of how cloud properties vary with environmental conditions can help evaluate some parameterizations used in models. However, sufficient data are not available to characterize how ice crystal properties vary as a function of environmental conditions. Furthermore, many of these assumptions are derived from historical datasets collected by in situ probes, namely optical array probes that can be contaminated by shattered artifacts generated by large particles shattering on the probe tips and inlets. Therefore this study has two main objectives. Prior estimates of ice crystal size distributions derived from 2D Cloud Probes (2DCs) have been artificially amplified by small ice crystals generated from the shattering of large ice crystals on the probe tips. Although anti-shatter tips and algorithms exist, there is considerable uncertainty in their effectiveness. Therefore, this thesis first examines the differences in ice crystal size distributions, and bulk and optical properties from adjacent 2DCs with standard and anti-shatter tips, and processed with and without anti-shattering algorithms. The measurements were obtained from the National Research Council of Canada Convair-580 during the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) and the National Center for Atmospheric Research C-130 during the 2011 Instrumentation Development and Education in Airborne Science 2011 (IDEAS-2011). The 2DC size distributions are compared with those from the Holographic Detector for Clouds (HOLODEC), which has anti-shatter tips and allows for identification of shattering through spatial statistics. The ratio of the number concentration N of particles with maximum dimensions 125 to 500 mum from the 2DC with

Peierls instability and optical properties of bilayer polyacene

Energy Technology Data Exchange (ETDEWEB)

Zhang, Longlong, E-mail: zhanglonglong@tyut.edu.cn [The College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024 (China); Xie, Shijie [School of Physics, Shandong University, Jinan 250100 (China)

2017-05-03

Highlights: • The Peierls instability of bilayer polyacene is discussed. • The external electric field effect on bilayer polyacene is discussed. • The pressure effect on bilayer polyacene is discussed. • The optical properties of bilayer polyacene are discussed. - Abstract: We reveal that bilayer polyacene can be the gapped state due to the intralayer Peierls instability. There are six topologically inequivalent Peierls-distorted structures and they are degenerate in energy. The external electric field can tune the Peierls gap and induce the semiconductor-to-metallic phase transitions. The optical conductivity spectra are calculated in an attempt to categorize the Peierls-distorted structures. The strength of the interlayer coupling essentially affects the electronic properties and the optical selection rules.

Bulk properties of the medium produced in relativistic heavy-ion collisions from the beam energy scan program

Science.gov (United States)

Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Ajitanand, N. N.; Alekseev, I.; Anderson, D. M.; Aoyama, R.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Behera, A.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Brown, D.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chankova-Bunzarova, N.; Chatterjee, A.; Chattopadhyay, S.; Chen, X.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Elsey, N.; Engelage, J.; Eppley, G.; Esha, R.; Esumi, S.; Evdokimov, O.; Ewigleben, J.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Federicova, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Hamad, A. I.; Hamed, A.; Harlenderova, A.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, T.; Huang, B.; Huang, X.; Huang, H. Z.; Humanic, T. J.; Huo, P.; Igo, G.; Jacobs, W. W.; Jentsch, A.; Jia, J.; Jiang, K.; Jowzaee, S.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Kochenda, L.; Kocmanek, M.; Kollegger, T.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kulathunga, N.; Kumar, L.; Kvapil, J.; Kwasizur, J. H.; Lacey, R.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, X.; Li, C.; Li, W.; Li, Y.; Lidrych, J.; Lin, T.; Lisa, M. A.; Liu, H.; Liu, P.; Liu, Y.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, S.; Luo, X.; Ma, G. L.; Ma, L.; Ma, Y. G.; Ma, R.; Magdy, N.; Majka, R.; Mallick, D.; Margetis, S.; Markert, C.; Matis, H. S.; Meehan, K.; Mei, J. C.; Miller, Z. W.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mizuno, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nie, M.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Nonaka, T.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Przybycien, M.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Ray, R. L.; Reed, R.; Rehbein, M. J.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Roth, J. D.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Salur, S.; Sandweiss, J.; Saur, M.; Schambach, J.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Schweid, B. R.; Seger, J.; Sergeeva, M.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, A.; Sharma, M. K.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Strikhanov, M.; Stringfellow, B.; Sugiura, T.; Sumbera, M.; Summa, B.; Sun, Y.; Sun, X. M.; Sun, X.; Surrow, B.; Svirida, D. N.; Tang, A. H.; Tang, Z.; Taranenko, A.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Trzeciak, B. A.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vasiliev, A. N.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, G.; Wang, Y.; Wang, F.; Wang, Y.; Webb, J. C.; Webb, G.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xu, J.; Xu, N.; Xu, Q. H.; Xu, Y. F.; Xu, Z.; Yang, Y.; Yang, Q.; Yang, C.; Yang, S.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, Z.; Zhang, X. P.; Zhang, J. B.; Zhang, S.; Zhang, J.; Zhang, Y.; Zhang, J.; Zhang, S.; Zhao, J.; Zhong, C.; Zhou, L.; Zhou, C.; Zhu, X.; Zhu, Z.; Zyzak, M.; STAR Collaboration

2017-10-01

We present measurements of bulk properties of the matter produced in Au+Au collisions at √{sN N}=7.7 ,11.5 ,19.6 ,27 , and 39 GeV using identified hadrons (π±, K±, p , and p ¯) from the STAR experiment in the Beam Energy Scan (BES) Program at the Relativistic Heavy Ion Collider (RHIC). Midrapidity (|y |<0.1 ) results for multiplicity densities d N /d y , average transverse momenta 〈pT〉 , and particle ratios are presented. The chemical and kinetic freeze-out dynamics at these energies are discussed and presented as a function of collision centrality and energy. These results constitute the systematic measurements of bulk properties of matter formed in heavy-ion collisions over a broad range of energy (or baryon chemical potential) at RHIC.

Radiation-optical properties of the glasses for the space application

International Nuclear Information System (INIS)

Akishin, A.I.; Tseplyaev, L.I.

2006-01-01

The data are presented and generalized on variations of optical properties of glass and light guides under simulative cosmic ionizing radiation. It is shown that changes in optical properties (coloration, bleaching, opacity, luminescence) under ionizing radiation are associated with color centers formation and annealing [ru

Thickness dependent structural, optical and electrical properties of Se85In12Bi3 nanochalcogenide thin films

Science.gov (United States)

Tripathi, Ravi P.; Zulfequar, M.; Khan, Shamshad A.

2018-04-01

Our aim is to study the thickness dependent effects on structure, electrical and optical properties of Se85In12Bi3 nanochalcogenide thin films. Bulk alloy of Se85In12Bi3 was synthesized by melt-quenching technique. The amorphous as well as glassy nature of Se85In12Bi3 chalcogenide was confirmed by non-isothermal Differential Scanning Calorimetry (DSC) measurements. The nanochalcogenide thin films of thickness 30, 60 and 90 nm were prepared on glass/Si wafer substrate using Physical Vapour Condensation Technique (PVCT). From XRD studies it was found that thin films have amorphous texture. The surface morphology and particle size of films were studied by Field Emission Scanning Electron Microscope (FESEM). From optical studies, different optical parameters were estimated for Se85In12Bi3 thin films at different thickness. It was found that the absorption coefficient (α) and extinction coefficient (k) increases with photon energy and decreases with film thickness. The optical absorption process followed the rule of indirect transitions and optical band gap were found to be increase with film thickness. The value of Urbach energy (Et) and steepness parameter (σ) were also calculated for different film thickness. For electrical studies, dc-conductivity measurement was done at different temperature and activation energy (ΔEc) were determined and found to be increase with film thickness.

Measuring the optical properties of IceCube drill holes

Directory of Open Access Journals (Sweden)

Rongen Martin

2016-01-01

Full Text Available The IceCube Neutrino Observatory consists of 5160 digital optical modules (DOMs in a cubic kilometer of deep ice below the South Pole. The DOMs record the Cherenkov light from charged particles interacting in the ice. A good understanding of the optical properties of the ice is crucial to the quality of the event reconstruction. While the optical properties of the undisturbed ice are well understood, the properties of the refrozen drill holes still pose a challenge. A new data-acquisition and analysis approach using light originating from LEDs within one DOM detected by the photomultiplier of the same DOM will be described. This method allows us to explore the scattering length in the immediate vicinity of the considered DOMs.

Nuclear matter with a pseudo-particle model: static bulk and surface properties

International Nuclear Information System (INIS)

Idier, D.; Benhassine, B.; Farine, M.; Remaud, B.; Sebille, F.

1993-01-01

Direct calculations of cold and hot nuclear matter (bulk and surface properties) are carried out within the frame of a pseudo-particle model using a gaussian decomposition of the distribution function. Comparisons with Hartree-Fock calculations, for a large class of effective interactions, show that such a model is reliable to reproduce accurately the equation of state of nuclear matter for large ranges of densities and temperatures. The number of gaussians per nucleon and the gaussian widths are critical parameters in that semi-classical model. (orig.)

Nuclear matter with a pseudo-particle model: static bulk and surface properties

Energy Technology Data Exchange (ETDEWEB)

Idier, D. (Lab. de Physique Nucleaire CNRS/IN2P3, Univ. de Nantes (France)); Benhassine, B. (Lab. de Physique Nucleaire CNRS/IN2P3, Univ. de Nantes (France)); Farine, M. (Lab. de Physique Nucleaire CNRS/IN2P3, Univ. de Nantes (France)); Remaud, B. (Lab. de Physique Nucleaire CNRS/IN2P3, Univ. de Nantes (France)); Sebille, F. (Lab. de Physique Nucleaire CNRS/IN2P3, Univ. de Nantes (France))

1993-11-15

Direct calculations of cold and hot nuclear matter (bulk and surface properties) are carried out within the frame of a pseudo-particle model using a gaussian decomposition of the distribution function. Comparisons with Hartree-Fock calculations, for a large class of effective interactions, show that such a model is reliable to reproduce accurately the equation of state of nuclear matter for large ranges of densities and temperatures. The number of gaussians per nucleon and the gaussian widths are critical parameters in that semi-classical model. (orig.)

Linking Aerosol Optical Properties Between Laboratory, Field, and Model Studies

Science.gov (United States)

Murphy, S. M.; Pokhrel, R. P.; Foster, K. A.; Brown, H.; Liu, X.

2017-12-01

The optical properties of aerosol emissions from biomass burning have a significant impact on the Earth's radiative balance. Based on measurements made during the Fourth Fire Lab in Missoula Experiment, our group published a series of parameterizations that related optical properties (single scattering albedo and absorption due to brown carbon at multiple wavelengths) to the elemental to total carbon ratio of aerosols emitted from biomass burning. In this presentation, the ability of these parameterizations to simulate the optical properties of ambient aerosol is assessed using observations collected in 2017 from our mobile laboratory chasing wildfires in the Western United States. The ambient data includes measurements of multi-wavelength absorption, scattering, and extinction, size distribution, chemical composition, and volatility. In addition to testing the laboratory parameterizations, this combination of measurements allows us to assess the ability of core-shell Mie Theory to replicate observations and to assess the impact of brown carbon and mixing state on optical properties. Finally, both laboratory and ambient data are compared to the optical properties generated by a prominent climate model (Community Earth System Model (CESM) coupled with the Community Atmosphere Model (CAM 5)). The discrepancies between lab observations, ambient observations and model output will be discussed.

Titania doping effect on superconducting properties of MgB{sub 2} bulk samples

Energy Technology Data Exchange (ETDEWEB)

Serrano, G; Serquis, A [Institute Balseiro - Centra Atomico Bariloche and CONICET, (8400) S. C. de Bariloche, Rio Negro (Argentina); Bridoux, G, E-mail: serranog@ib.cnea.gov.a [Institute Balseiro - Centra Atomico Bariloche, (8400) S. C. de Bariloche, Rio Negro (Argentina)

2009-05-01

In this work we study the microstructural and superconducting properties of doped and undoped bulk MgB{sub 2} samples prepared by solid-state reaction, with 0 and 2.5 %at. nominal TiO{sub 2} nanotubes contents, annealed at different temperatures in the 750-900 deg. C range. We discuss the T{sub c}, J{sub c} and H{sub c2} performance and their correlation with the different synthesis parameters.

Structure and optical properties of cored wurtzite (Zn,Mg)O heteroepitaxial nanowires

International Nuclear Information System (INIS)

Heo, Y.W.; Abernathy, C.; Pruessner, K.; Sigmund, W.; Norton, D.P.; Overberg, M.; Ren, F.; Chisholm, M.F.

2004-01-01

The synthesis, structure, and optical properties of one-dimensional heteroepitaxial cored (Zn,Mg)O semiconductor nanowires grown by a catalyst-driven molecular beam epitaxy technique are discussed. The structures form spontaneously in a Zn, Mg and O 2 /O 3 flux, consisting of a single crystal, Zn-rich Zn 1-x Mg x O(x 1-y Mg y O(y>>0.02) sheath. High resolution Z-contrast scanning transmission electron microscopy shows core diameters as small as 4 nm. The cored structure forms spontaneously under constant flux due to a bimodal growth mechanism in which the core forms via bulk like vapor-liquid-solid growth, while the outer sheath grows as a heteroepitaxial layer. Temperature-dependent photoluminescence shows a slight blueshift in the near band edge peak, which is attributed to a few percent Mg doping in the nanoscale ZnO core. The catalyst-driven molecular beam epitaxy technique provides for site-specific nanorod growth on arbitrary substrates

Effective-mass model and magneto-optical properties in hybrid perovskites

OpenAIRE

Yu, Z. G.

2016-01-01

Hybrid inorganic-organic perovskites have proven to be a revolutionary material for low-cost photovoltaic applications. They also exhibit many other interesting properties, including giant Rashba splitting, large-radius Wannier excitons, and novel magneto-optical effects. Understanding these properties as well as the detailed mechanism of photovoltaics requires a reliable and accessible electronic structure, on which models of transport, excitonic, and magneto-optical properties can be effici...

Structural, optical and thermal properties of nanoporous aluminum

International Nuclear Information System (INIS)

Ghrib, Taher

2015-01-01

Highlights: • A simple electrochemical technique is presented and used to manufacture a porous aluminum layer. • Manufactured pores of 40 nm diameter and 200 nm depth are filled by nanocrystal of silicon and graphite. • Dimensions of pores increase with the anodization current which ameliorate the optical and thermal properties. • A new thermal method is presented which permit to determine the pores density and the layer thickness. • All properties show that the manufactured material can be used with success in solar cells. - Abstract: In this work the structural, thermal and optical properties of porous aluminum thin film formed with various intensities of anodization current in sulfuric acid are highlighted. The obtained pores at the surface are filled by sprayed graphite and nanocrystalline silicon (nc-Si) thin films deposited by plasma enhancement chemical vapor deposition (PECVD) which the role is to improve its optical and thermal absorption giving a structure of an assembly of three different media such as deposited thin layer (graphite or silicon)/(porous aluminum layer filled with the deposited layer)/(Al sample). The effect of anodization current on the microstructure of porous aluminum and the effect of the deposited layer were systematically studied by atomic force microscopy (AFM), transmission electron microscopy (TEM) and Raman spectroscopy. The thermal properties such as the thermal conductivity (K) and thermal diffusivity (D) are determined by the photothermal deflection (PTD) technique which is a non destructive technique. Based on this full characterization, it is demonstrated that the thermal and optical characteristics of these films are directly correlated to their micro-structural properties

Silicene-terminated surface of calcium and strontium disilicides: properties and comparison with bulk structures by computational methods

Science.gov (United States)

Brázda, Petr; Mutombo, Pingo; Ondráček, Martin; Corrêa, Cinthia Antunes; Kopeček, Jaromír; Palatinus, Lukáš

2018-05-01

The bulk and surface structures of calcium and strontium disilicides are investigated by computational methods using density functional theory. The investigated structures are R6, R3 and P1-CaSi2 and P1-SrSi2. The investigated properties are the cleavage energy at the silicene sheet, buckling of the bulk and surface silicene layers, charge transfer from calcium to silicon, band structure of bulk and surface-terminated structures and adsorption energies on H atoms and H2 molecules on the silicene-terminated surface of the R3 phase. The cleavage energy at the silicene surface is low in all cases. Structures P1-CaSi2 and R3-CaSi2 contain silicene sheets with different coordination to Ca, while R6-CaSi2 contains both types of the sheets. It is shown that the properties of the two types of silicene-like sheets in R6-CaSi2 are similar to those of the corresponding sheets in P1-CaSi2 and R3-CaSi2, and the thermodynamically stable R6 phase is a good candidate for experimental investigation of silicene-terminated surface in calcium disilicide.

First-principles study of structural, electronic, and optical properties of surface defects in GaAs(001) - β2(2x4)

Science.gov (United States)

Bacuyag, Dhonny; Escaño, Mary Clare Sison; David, Melanie; Tani, Masahiko

2018-06-01

We performed first-principles calculations based on density functional theory (DFT) to investigate the role of point defects in the structural, electronic, and optical properties of the GaAs(001)- β2(2x4). In terms of structural properties, AsGa is the most stable defect structure, consistent with experiments. With respect to the electronic structure, band structures revealed the existence of sub-band and midgap states for all defects. The induced sub-bands and midgap states originated from the redistributions of charges towards these defects and neighboring atoms. The presence of these point defects introduced deep energy levels characteristic of EB3 (0.97 eV), EL4 (0.52 eV), and EL2 (0.82 eV) for AsGa, GaAs, GaV, respectively. The optical properties are found to be strongly related to these induced gap states. The calculated onset values in the absorption spectra, corresponding to the energy gaps, confirmed the absorption below the known bulk band gap of 1.43 eV. These support the possible two-step photoabsorption mediated by midgap states as observed in experiments.

Broadband optical characterization of material properties

DEFF Research Database (Denmark)

Nielsen, Otto Højager Attermann

the applicability of optical techniques for this purpose, the fermentation of milk into yogurt has been used as a model system. Studies have been conducted on commercially available products, but also of on-line measurement of the fermentation process. The second process is from the aquaculture industry...... reports on the design and operation of the different measurement techniques together with the necessary theoretical background for the industrial applications. For the purpose of milk fermentation this work has demonstrated that the reduced scattering properties of milk change significantly throughout...... the fermentation process. It has also been shown that the optical inspection methods sense changes to structural properties before any are detected by traditional mechanical rheology. Finally, the developed hyperspectral imaging system was used to quantify the content of astaxanthin in fish feed, and performed...

Elastic properties of superconducting bulk metallic glasses; Elastische Eigenschaften von supraleitenden massiven metallischen Glaesern

Energy Technology Data Exchange (ETDEWEB)

Hempel, Marius

2015-07-01

Within the framework of this thesis the elastic properties of a superconducting bulk metallic glass between 10 mK and 300 K were first investigated. In order to measure the entire temperature range, in particular the low temperature part, new experimental techniques were developed. Using an inductive readout scheme for a double paddle oscillator it was possible to determine the internal friction and the relative change of sound velocity of bulk metallic glasses with high precision. This allowed for a detailed comparison of the data with different models. The analysis focuses on the low temperature regime where the properties of glassy materials are governed by atomic tunneling systems as described by the tunneling model. The influence of conduction electrons in the normal conducting state and quasiparticles in the superconducting state of the glass were accounted for in the theoretical description, resulting in a good agreement over a large temperature range between measured data and prediction of the tunneling model. This allowed for a direct determination of the coupling constant between electrons and tunneling systems. In the vicinity of the transition temperature Tc the data can only be described if a modified distribution function of the tunneling parameters is applied.

EFFECT OF THE TEMPERATURE ON THE FRICTION AND WEAR PROPERTIES OF BULK AMORPHOUS ALLOY

OpenAIRE

DAWIT ZENEBE SEGU; PYUNG HWANG; SEOCK-SAM KIM

2014-01-01

The present paper report the results of an experimental investigation of the temperature effect on the sliding friction and wear properties of the bulk metallic glass (BMG). To improve the friction and wear properties of the BMG, the disk specimens were developed in the alloy system of Fe67.6C7.1Si3.3B5.5P8.7Cr2.3Mo2.6Al2Co1.0 using hot metal and industrial ferro-alloys. The friction and wear test was performed using flat-on-flat contact configuration of unidirectional tribometer and Si3N4 ce...

Linear and Nonlinear Optical Properties of Micrometer-Scale Gold Nanoplates

International Nuclear Information System (INIS)

Liu Xiao-Lan; Peng Xiao-Niu; Yang Zhong-Jian; Li Min; Zhou Li

2011-01-01

Micrometer-scale gold nanoplates have been synthesized in high yield through a polyol process. The morphology, crystal structure and linear optical extinction of the gold nanoplates have been characterized. These gold nanoplates are single-crystalline with triangular, truncated triangular and hexagonal shapes, exhibiting strong surface plasmon resonance (SPR) extinction in the visible and near-infrared (NIR) region. The linear optical properties of gold nanoplates are also investigated by theoretical calculations. We further investigate the nonlinear optical properties of the gold nanoplates in solution by Z-scan technique. The nonlinear absorption (NLA) coefficient and nonlinear refraction (NLR) index are measured to be 1.18×10 2 cm/GW and −1.04×10 −3 cm 2 /GW, respectively. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Optical properties of cells with melanin

Science.gov (United States)

Rohde, Barukh; Coats, Israel; Krueger, James; Gareau, Dan

2014-02-01

The optical properties of pigmented lesions have been studied using diffuse reflectance spectroscopy in a noninvasive configuration on optically thick samples such as skin in vivo. However, it is difficult to un-mix the effects of absorption and scattering with diffuse reflectance spectroscopy techniques due to the complex anatomical distributions of absorbing and scattering biomolecules. We present a device and technique that enables absorption and scattering measurements of tissue volumes much smaller than the optical mean-free path. Because these measurements are taken on fresh-frozen sections, they are direct measurements of the optical properties of tissue, albeit in a different hydration state than in vivo tissue. Our results on lesions from 20 patients including melanomas and nevi show the absorption spectrum of melanin in melanocytes and basal keratinocytes. Our samples consisted of fresh frozen sections that were unstained. Fitting the spectrum as an exponential decay between 500 and 1100 nm [mua = A*exp(-B*(lambda-C)) + D], we report on the fit parameters of and their variation due to biological heterogeneity as A = 4.20e4 +/- 1.57e5 [1/cm], B = 4.57e-3 +/- 1.62e-3 [1/nm], C = 210 +/- 510 [nm] , D = 613 +/- 534 [1/cm]. The variability in these results is likely due to highly heterogeneous distributions of eumelanin and pheomelanin.

Channeling Polyolefin Molecular Structure - Bulk Property Correlation Strategies for Industrial Applicability

Science.gov (United States)

Hule, Rohan; Thurman, Derek; Doufas, Antonios

Polyolefins occupy a significant volume of the polymer products portfolio in commodity and high value applications. Quantifying and optimizing structure-property relationships enables growth in new markets. It is well recognized that coupling lab-based, comprehensive methodologies with bulk properties of interest to industrial environments offer the greatest potential of technology advancement, ultimately leading to commercial success. It is imperative to recognize the existing gap of knowledge translation between lab measurements and industrial-scale operability. This study highlights experimental HDPEs synthesized from dual, single-site, co-supported catalysts that exhibit enhanced solid-state properties such as stiffness, impact and ESCR surpassing conventional trends. Commercial resins across distinct sub-families were included as well. Commonality amongst these resins is bimodality and broad MW distribution with well-defined splits and spreads. Investigations on commercially relevant parameters such as melt strength, melt elasticity and shear thinning established excellent performance for experimental bimodals, corroborating potential benefits compared to commercial HDPEs. To summarize, the effort highlights well-recognized pathways such as improvements in mechanical and melt properties that can be attributed to apposite tuning of polymer chain architecture and MW distribution with implications across myriad markets. Ultimately, this may serve as a pathway for producing innovative products that deliver business success and growth.

Chiral nanophotonics chiral optical properties of plasmonic systems

CERN Document Server

Schäferling, Martin

2017-01-01

This book describes the physics behind the optical properties of plasmonic nanostructures focusing on chiral aspects. It explains in detail how the geometry determines chiral near-fields and how to tailor their shape and strength. Electromagnetic fields with strong optical chirality interact strongly with chiral molecules and, therefore, can be used for enhancing the sensitivity of chiroptical spectroscopy techniques. Besides a short review of the latest results in the field of plasmonically enhanced enantiomer discrimination, this book introduces the concept of chiral plasmonic near-field sources for enhanced chiroptical spectroscopy. The discussion of the fundamental properties of these light sources provides the theoretical basis for further optimizations and is of interest for researchers at the intersection of nano-optics, plasmonics and stereochemistry. .

Gold nanorods-silicone hybrid material films and their optical limiting property

Science.gov (United States)

Li, Chunfang; Qi, Yanhai; Hao, Xiongwen; Peng, Xue; Li, Dongxiang

2015-10-01

As a kind of new optical limiting materials, gold nanoparticles have optical limiting property owing to their optical nonlinearities induced by surface plasmon resonance (SPR). Gold nanorods (GNRs) possess transversal SPR absorption and tunable longitudinal SPR absorption in the visible and near-infrared region, so they can be used as potential optical limiting materials against tunable laser pulses. In this letter, GNRs were prepared using seed-mediated growth method and surface-modified by silica coating to obtain good dispersion in polydimethylsiloxane prepolymers. Then the silicone rubber films doped with GNRs were prepared after vulcanization, whose optical limiting property and optical nonlinearity were investigated. The silicone rubber samples doped with more GNRs were found to exhibit better optical limiting performance.

Laboratory Studies of the Optical Properties and Condensation Processes of Cosmic Dust Particles

Science.gov (United States)

Abbas, Mian M.; Craven, Paul D.; Spann, James F.; Tankosic, Dragana; Six, N. Frank (Technical Monitor)

2002-01-01

A laboratory facility for levitating single isolated dust particles in an electrodynamics balance has been developing at NASA/Marshall Space Flight Center for conducting a variety of experimental, of astrophysical interest. The objective of this research is to employ this innovative experimental technique for studies of the physical and optical properties of the analogs of cosmic grains of 0.2-10 micron size in a chamber with controlled pressure/temperatures simulating astrophysical environments. In particular, we will carry out three classes of experiments to investigate the microphysics of the analogs of interstellar and interplanetary dust grains. (1) Charge characteristics of micron size single dust grains to determine the photoelectric efficiencies, yields, and equilibrium potentials when exposed to UV radiation. These measurements will provide the much-needed photoelectric emission data relating to individual particles as opposed to that for the bulk materials available so far. (2) Infrared optical properties of dust particles obtained by irradiating the particles with radiation from tunable infrared diode lasers and measuring the scattered radiation. Specifically, the complex refractive indices, the extinction coefficients, the scattering phase functions, and the polarization properties of single dust grains of interest in interstellar environments, in the 1-25 micron spectral region will be determined. (3) Condensation experiments to investigate the deposition of volatile gases on colder nucleated particles in dense interstellar clouds and lower planetary atmospheres. The increase in the mass or m/q ratio due to condensation on the particle will be monitored as a function of the dust particle temperature and the partial pressure of the injected volatile gas. The measured data wild permit determination of the sticking efficiencies of volatile gases of astrophysical interest. Preliminary results based on photoelectric emission experiments on 0.2-6.6 micron

Preparation and optical and electrical evaluation of bulk SiO2 sonogel hybrid composites and vacuum thermal evaporated thin films prepared from molecular materials derived from (Fe, Co) metallic phthalocyanines and 1,8 dihydroxiantraquinone compounds

International Nuclear Information System (INIS)

Sanchez Vergara, Maria Elena; Morales-Saavedra, Omar G.; Ontiveros-Barrera, Fernando G.; Torres-Zuniga, Vicente; Ortega-Martinez, Roberto; Ortiz Rebollo, Armando

2009-01-01

Semiconducting molecular material of PcFe(CN)L1 and PcCo(CN)L1 (L1 = 1,8 dihydroxianthraquinone), PcFe(CN)L2 and PcCo(CN)L2 (L2 = double potassium salt of 1,8 dihydroxianthraquinone) have been successfully used to prepare thin film and bulk sol-gel hybrid optical materials. These samples were developed according to the vacuum thermal evaporation technique and the catalyst-free sonogel route, respectively. Thin films samples were deposited on Corning glass substrates and crystalline silicon wafers and were characterized by infrared (FTIR), Raman and ultraviolet-visible (UV-vis) spectroscopies. IR-spectroscopy and Raman studies unambiguously confirmed that the molecular material thin films exhibit the same intra-molecular bonds, which suggests that the thermal evaporation process does not alter these bonds significantly. These results show that it is possible to deposit molecular materials of PcFe(CN)L2 and PcCo(CN)L2 on Corning glass substrates and silicon wafers. From the UV-vis studies the optical band gap (E g ) was evaluated. The effect of temperature on conductivity was also evaluated in these samples. Finally, the studied molecular systems dissolved at different concentrations in tetrahydrofuran (THF) were successfully embedded into a highly pure SiO 2 sonogel network generated via sonochemical reactions to form several solid state, optically active sol-gel hybrid glasses. By this method, homogeneous and stable hybrid monoliths suitable for optical characterization can be produced. The linear optical properties of these amorphous bulk structures were determined by the Brewster angle method and by absorption-, Raman- and photoluminescent (PL)-spectroscopies, respectively

Optical properties of spherical gold mesoparticles

DEFF Research Database (Denmark)

Evlyukhin, A. B.; Kuznetsov, A. I.; Novikov, S. M.

2012-01-01

Optical properties of spherical gold particles with diameters of 150-650 nm (mesoparticles) are studied by reflectance spectroscopy. Particles are fabricated by laser-induced transfer of metallic droplets onto metal and dielectric substrates. Contributions of higher multipoles (beyond...

Preparation and magnetic properties of anisotropic bulk MnBi/NdFeB hybrid magnets

Science.gov (United States)

Ma, Y. L.; Liu, X. B.; Nguyen, V. V.; Poudyal, N.; Yue, M.; Liu, J. P.

2016-08-01

Anisotropic hybrid bulk magnets of MnBi/NdFeB with different composition ratio have been prepared with starting MnBi and Nd2Fe14B powders as well as epoxy resin as a binder in case it is needed to form bulk samples. It has been found that the ratio between the two phases in content has a remarkable influence on the magnetic properties, the thermal stability and the density of the bulk magnets. With increasing MnBi content the binder addition can be reduced. When the MnBi content is larger than 30 wt%, no binder is needed. On the other hand, the coercivity and saturation magnetization were increased significantly with increasing NdFeB content. When the NdFeB content was increased from 0% to 50%, the maximum energy product was enhanced from 4.7 to 10.0 MGOe, respectively. The energy product then decreased gradually with the NdFeB content due to the reduced density of the hybrid magnet. The thermal stability measurements showed that the temperature coefficient of coercivity grew with the MnBi content and became positive with MnBi=80 wt%.

Effects of ionizing radiations on the optical properties of ionic copper-activated sol-gel silica glasses

Science.gov (United States)

Al Helou, Nissrine; El Hamzaoui, Hicham; Capoen, Bruno; Ouerdane, Youcef; Boukenter, Aziz; Girard, Sylvain; Bouazaoui, Mohamed

2018-01-01

Studying the impact of radiations on doped silica glasses is essential for several technological applications. Herein, bulk silica glasses, activated with various concentrations of luminescent monovalent copper (Cu+), have been prepared using the sol-gel technique. Thereafter, these glasses were subjected to X- or γ-rays irradiation at 1 MGy(SiO2) accumulated dose. The effect of these ionizing radiations on the optical properties of these glasses, as a function of the Cu-doping content, were investigated using optical absorption and photoluminescence spectroscopies. Before any irradiation, the glass with the lowest copper concentration exhibits blue and green luminescence bands under UV excitation, suggesting that Cu+ ions occupy both cubic and tetragonal symmetry sites. However, at higher Cu-doping level, only the green emission band exists. Moreover, we showed that the hydroxyl content decreases with increasing copper doping concentration. Both X and γ radiation exposures induced visible absorption due to HC1 color centers in the highly Cu-doped glasses. In the case of the lower Cu-doped glass, the Cu+ sites with a cubic symmetry are transformed into sites with tetragonal symmetry.

Optical properties of nitride nanostructures

Energy Technology Data Exchange (ETDEWEB)

Cantarero, A.; Cros, A.; Garro, N.; Gomez-Gomez, M.I.; Garcia, A.; Lima, M.M. de [Materials Science Institute, University of Valencia, PO Box 22085, 46071 Valencia (Spain); Daudin, B. [Departement de Recherche Fondamentale sur la Matiere Condensee, SPMM, CEA/Grenoble, 17 Rue des Martyrs, 38054 Grenoble (France); Rizzi, A.; Denker, C.; Malindretos, J. [IV. Physikalisches Institut, Georg August Universitaet Goettingen, 37073 Goettingen (Germany)

2011-01-15

In this paper we review some recent results on the optical properties of nitride nanostructures, in particular on GaN quantum dots (QDs) and InN nanocolumns (NCs). First, we will give a brief introduction on the particularities of vibrational modes of wurtzite. The GaN QDs, embedded in AlN, were grown by molecular beam epitaxy (MBE) in the Stransky-Krastanov mode on c- and a-plane 6H-SiC. We have studied the optical properties by means of photoluminescence (PL) and performed Raman scattering measurements to analyze the strain relaxation in the dots and the barrier, the effect of the internal electric fields, and the influence of specific growth parameters, like the influence of capping or the spacer on the relaxation of the QDs. A theoretical model, based on continuous elastic theory, were developed to interpret the Raman scattering results. On the other hand, InN NCs have been grown by MBE in the vapor-liquid-solid mode using Au as a catalyst. The nanocolumns have different morphology depending on the growth conditions. The optical properties can be correlated to the morphology of the samples and the best growth conditions can be selected. We observe, from the analysis of the Raman data in InN NCs, the existence of two space regions contributing to the scattering: the surface and the inner region. From the inner region, uncoupled phonon modes are clearly observed, showing the high crystal quality and the complete relaxation of the NCs (no strain). The observation of a LO-phonon-plasmon couple in the same spectra is a fingerprint of the accumulation layer predicted at the surface of the nanocolumns. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Centrality dependence of bulk fireball properties in √(sNN)=200 GeV Au-Au collisions

International Nuclear Information System (INIS)

Rafelski, Johann; Letessier, Jean; Torrieri, Giorgio

2005-01-01

We explore the centrality dependence of the properties of the dense hadronic matter created in √(s NN )=200 GeV Au-Au collisions at the Relativistic Heavy Ion Collider. Using the statistical hadronization model, we fit particle yields known for 11 centrality bins. We present the resulting model parameters, rapidity yields of physical quantities, and the physical properties of bulk matter at hadronization as function of centrality. We discuss the production of strangeness and entropy

Optical characterization of bulk Zn1-xBexTe crystals

International Nuclear Information System (INIS)

Shih, Y C; Huang, Y S; Firszt, F; Legowski, S; Meczynska, H; Tiong, K K

2008-01-01

This paper presents an optical characterization of three bulk sphalerite Zn 1-x Be x Te crystals grown by the modified high pressure Bridgman method. The study was conducted in the near-band-edge interband transition regime using low temperature photoluminescence (PL), temperature-dependent contactless electroreflectance (CER) and/or photoreflectance (PR) in the temperature range of 15-400 K, and surface photovoltage spectroscopy (SPS) at room temperature. PL spectra at low temperatures of the samples investigated consist of an excitonic line, a band due to recombination of free electrons with holes located at shallow acceptors and a broad band related to recombination through deeper level defects. The band-edge excitonic transitions have been observed in the CER/PR spectra. The fundamental transition energies E 0 are determined via lineshape fits to the CER/PR spectra. The values of E 0 at room temperature obtained from CER/PR spectra correspond well to that determined from SPS measurements, and the Be contents x of the samples are determined using a linear equation which describes the room temperature band gap dependence on composition for the Zn 1-x Be x Te alloy system. The parameters describing the temperature dependence of the band-edge excitonic transition energies are evaluated and discussed

Dispersion properties of plasma cladded annular optical fiber

Science.gov (United States)

KianiMajd, M.; Hasanbeigi, A.; Mehdian, H.; Hajisharifi, K.

2018-05-01

One of the considerable problems in a conventional image transferring fiber optic system is the two-fold coupling of propagating hybrid modes. In this paper, using a simple and practical analytical approach based on exact modal vectorial analysis together with Maxwell's equations, we show that applying plasma as a cladding medium of an annular optical fiber can remove this defect of conventional fiber optic automatically without any external instrument as the polarization beam splitter. Moreover, the analysis indicates that the presence of plasma in the proposed optical fiber could extend the possibilities for controlling the propagation property. The proposed structure presents itself as a promising route to advanced optical processing and opens new avenues in applied optics and photonics.

Frictional and Optical Properties of Diamond-Like-Carbon Coatings on Polycarbonate

International Nuclear Information System (INIS)

Lin Zeng; Gao Ding; Ba Dechun; Wang Feng; Liu Chunming

2013-01-01

In this work, diamond-like-carbon (DLC) films were deposited onto polycarbonate (PC) substrates by radio-frequency plasma-enhanced chemical vapor deposition (RF PECVD), and silicon films were prepared between DLC and PC substrates by magnetron sputtering deposition so as to improve the adhesion of the DLC films. The deposited films were investigated by means of field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Subsequently, the following frictional and optical properties of the films were measured: the friction coefficient by using a ball-on-disk tribometer, the scratch hardness by using a nano-indenter, the optical transmittance by using a UV/visible spectrometer. The effects of incident power upon the frictional and optical properties of the films were investigated. Films deposited at low incident powers showed large optical gaps, which decreased with increasing incident power. The optical properties of DLC films correlated to the sp 2 content of the coatings. High anti-scratch properties were obtained at higher values of incident power. The anti-scratch properties of DLC films correlated to the sp 3 content of the coatings

Linear and nonlinear optical properties of borate crystals as ...

Indian Academy of Sciences (India)

Unknown

crystal series, with an accuracy acceptable for materials development/design, and answer the questions often ... Optical property; nonlinear optical crystals; first principles calculation. 1. ..... system, and is not in concept suitable to excitation pro-.

Preparation and magnetic properties of anisotropic bulk MnBi/NdFeB hybrid magnets

International Nuclear Information System (INIS)

Ma, Y.L.; Liu, X.B.; Nguyen, V.V.; Poudyal, N.; Yue, M.; Liu, J.P.

2016-01-01

Anisotropic hybrid bulk magnets of MnBi/NdFeB with different composition ratio have been prepared with starting MnBi and Nd 2 Fe 14 B powders as well as epoxy resin as a binder in case it is needed to form bulk samples. It has been found that the ratio between the two phases in content has a remarkable influence on the magnetic properties, the thermal stability and the density of the bulk magnets. With increasing MnBi content the binder addition can be reduced. When the MnBi content is larger than 30 wt%, no binder is needed. On the other hand, the coercivity and saturation magnetization were increased significantly with increasing NdFeB content. When the NdFeB content was increased from 0% to 50%, the maximum energy product was enhanced from 4.7 to 10.0 MGOe, respectively. The energy product then decreased gradually with the NdFeB content due to the reduced density of the hybrid magnet. The thermal stability measurements showed that the temperature coefficient of coercivity grew with the MnBi content and became positive with MnBi=80 wt%. - Highlights: • Anisotropic bulk hybrid MnBi/NdFeB magnets were prepared. • MnBi content affected the density and coercivity temperature coefficient positively. • An energy product (BH) max of 10 MGOe was obtained at NdFeB content of 50 wt%.

Preparation and magnetic properties of anisotropic bulk MnBi/NdFeB hybrid magnets

Energy Technology Data Exchange (ETDEWEB)

Ma, Y.L. [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); College of Metallurgical and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331 (China); Liu, X.B.; Nguyen, V.V.; Poudyal, N. [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Yue, M. [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Liu, J.P., E-mail: pliu@uta.edu [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States)

2016-08-01

Anisotropic hybrid bulk magnets of MnBi/NdFeB with different composition ratio have been prepared with starting MnBi and Nd{sub 2}Fe{sub 14}B powders as well as epoxy resin as a binder in case it is needed to form bulk samples. It has been found that the ratio between the two phases in content has a remarkable influence on the magnetic properties, the thermal stability and the density of the bulk magnets. With increasing MnBi content the binder addition can be reduced. When the MnBi content is larger than 30 wt%, no binder is needed. On the other hand, the coercivity and saturation magnetization were increased significantly with increasing NdFeB content. When the NdFeB content was increased from 0% to 50%, the maximum energy product was enhanced from 4.7 to 10.0 MGOe, respectively. The energy product then decreased gradually with the NdFeB content due to the reduced density of the hybrid magnet. The thermal stability measurements showed that the temperature coefficient of coercivity grew with the MnBi content and became positive with MnBi=80 wt%. - Highlights: • Anisotropic bulk hybrid MnBi/NdFeB magnets were prepared. • MnBi content affected the density and coercivity temperature coefficient positively. • An energy product (BH){sub max} of 10 MGOe was obtained at NdFeB content of 50 wt%.

Optical Properties of Nanoparticles and Nanocomposites

CSIR Research Space (South Africa)

Kumbhakar, P

2014-01-01

Full Text Available of ceria nanoparticles and degradation of Congo red (CR) dye under the visible light irradiation. We are very much happy to note the research progress on the techniques of synthesis, characterization, and optical properties of nanostructured materials. Also...

Constitutive Modeling of the Mechanical Properties of Optical Fibers

Science.gov (United States)

Moeti, L.; Moghazy, S.; Veazie, D.; Cuddihy, E.

1998-01-01

Micromechanical modeling of the composite mechanical properties of optical fibers was conducted. Good agreement was obtained between the values of Young's modulus obtained by micromechanics modeling and those determined experimentally for a single mode optical fiber where the wave guide and the jacket are physically coupled. The modeling was also attempted on a polarization-maintaining optical fiber (PANDA) where the wave guide and the jacket are physically decoupled, and found not to applicable since the modeling required perfect bonding at the interface. The modeling utilized constituent physical properties such as the Young's modulus, Poisson's ratio, and shear modulus to establish bounds on the macroscopic behavior of the fiber.

Structural and optical properties of Ni doped ZnSe nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Yadav, Kanta; Dwivedi, Y.; Jaggi, Neena, E-mail: neena_jaggi@rediffmail.com

2015-02-15

In the present work synthesis of ZnSe:Ni nanoparticles using a simple solvothermal method has been discussed. The structural characterizations of as synthesized materials were done by powder X-ray diffraction (XRD), Transmission electron microscope (TEM) and High resolution transmission microscope (HRTEM) imaging techniques, which revealed formation of core–shell nanoparticles with crystallite size 2–4 nm. The structural parameters such as lattice constants, internal strain, dislocation density etc. of ZnSe and Ni doped ZnSe nanocrystals were estimated. Nickel doping in ZnSe host is verified by the Raman spectroscopy. Optical properties were diagnosed by UV–vis absorption and photoluminescence (PL) techniques. The observed blue-shift in UV–vis absorption edge of the prepared sample of ZnSe as compared to its value for the bulk counterpart indicates formation of nanosized particles. PL spectra of Ni{sup 2+} doped samples indicate red-shift and improved emission intensity. - Highlights: • Synthesis of core shell structures of the ZnSe by simple approach. • Enhancement of the photoluminescence emission with the increase in the concentration of Ni a transition metal into the host material. • Increase in the dislocation density and strain with decrease in grain size.

Characterization of bulk and shear properties of basmati and non-basmati rice flour.

Science.gov (United States)

Jan, Shumaila; Ghoroi, Chinmay; Saxena, Dharmesh Chandra

2018-01-01

Flours are often unstable in relation to their flow performance, which is evident when a free-flowing material ceases to flow and the processing, handling, and production parameters depend on the inherent powder characteristics and their bulk behaviour. The present study was conducted to compare the flowability of basmati and non-basmati rice flour affecting bulk handling, which could be related to its particle size, shape and surface roughness (measured by atomic force microscopy) as well as bulk and shear properties, depending upon the processing conditions. Particle size (171.1-171.9 μm) of both samples was not significantly different. However, the flowability of the non-basmati rice flour was significantly affected by its particle shape (circularity 0.487), surface roughness (124.23 nm) and compressibility (25.32%) in comparison to basmati rice flour (circularity 0.653, surface roughness 113.59 nm and compressibility 21.09%), making it more cohesive than basmati rice flour. Also, basic flow energy was significantly higher in non-basmati flour, thus requiring more energy (147.54 mJ) to flow than basmati rice flour (130.15 mJ). Overall, flowability was analysed by applying three different pressures (3, 6 and 9 kPa), among which non-basmati rice flour was found to be less flowable (flow function coefficient (FFC) 2.33 at 9 kPa) in comparison to basmati (FFC 3.35 at 9 kPa), making bulk handling difficult. This study could be useful in designing processing equipment, hoppers and silos for rice flour handling. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Electronic structure and optical properties of AIN under high pressure

International Nuclear Information System (INIS)

Li Zetao; Dang Suihu; Li Chunxia

2011-01-01

We have calculated the electronic structure and optical properties of Wurtzite structure AIN under different high pressure with generalized gradient approximation (GGA) in this paper. The total energy, density of state, energy band structure and optical absorption and reflection properties under high pressure are calculated. By comparing the changes of the energy band structure, we obtained AIN phase transition pressure for 16.7 GPa, which is a direct band structure transforming to an indirect band structure. Meanwhile, according to the density of states distribution and energy band structure, we analyzed the optical properties of AIN under high-pressure, the results showed that the absorption spectra moved from low-energy to high-energy. (authors)

Geometrical-optics code for computing the optical properties of large dielectric spheres.

Science.gov (United States)

Zhou, Xiaobing; Li, Shusun; Stamnes, Knut

2003-07-20

Absorption of electromagnetic radiation by absorptive dielectric spheres such as snow grains in the near-infrared part of the solar spectrum cannot be neglected when radiative properties of snow are computed. Thus a new, to our knowledge, geometrical-optics code is developed to compute scattering and absorption cross sections of large dielectric particles of arbitrary complex refractive index. The number of internal reflections and transmissions are truncated on the basis of the ratio of the irradiance incident at the nth interface to the irradiance incident at the first interface for a specific optical ray. Thus the truncation number is a function of the angle of incidence. Phase functions for both near- and far-field absorption and scattering of electromagnetic radiation are calculated directly at any desired scattering angle by using a hybrid algorithm based on the bisection and Newton-Raphson methods. With these methods a large sphere's absorption and scattering properties of light can be calculated for any wavelength from the ultraviolet to the microwave regions. Assuming that large snow meltclusters (1-cm order), observed ubiquitously in the snow cover during summer, can be characterized as spheres, one may compute absorption and scattering efficiencies and the scattering phase function on the basis of this geometrical-optics method. A geometrical-optics method for sphere (GOMsphere) code is developed and tested against Wiscombe's Mie scattering code (MIE0) and a Monte Carlo code for a range of size parameters. GOMsphere can be combined with MIE0 to calculate the single-scattering properties of dielectric spheres of any size.

Optical properties of stabilized copper nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Mohindroo, Jeevan Jyoti, E-mail: jjmdav@gmail.com [Punjab Technical University, Kapurthala Punjab (India); Department of Chemistry, DAV College, Amritsar, Punjab India (India); Garg, Umesh Kumar, E-mail: Umeshkgarg@gmail.com [Punjab Technical University, Kapurthala Punjab (India); Guru Teg Bahadur Khalsa College of IT, Malout, Punjab (India); Sharma, Anshul Kumar [Department of Physics, Guru Nanak Dev University, Amritsar 143005 (India)

2016-05-06

Optical studies involving calculation of Band Gap of the synthesized copper nanoparticles were carried out in the wavelength range of 500 to 650 nm at room temperature, the particles showed high absorption at 550 nm indicating their good absorptive properties. In this method water is used as the medium for reduction of copper ions in to copper Nanoparticles the stabilization of copper Nanoparticles was studied with starch both as a reductant and stabilizer,. The reaction mixture was heated using a kitchen microwave for about 5 minutes to attain the required temp for the reaction. The pH of the solution was adjusted to alkaline using 5% solution of NaOH. Formation of Copper Nanoparticles was indicated by change in color of the solution from blue to yellowish black which is supported by the UV absorption at 570 nm.the synthesized particles were washed with water and alcohol. The optical properties depend upon absorption of radiations which in turn depends upon ratio of electrons and holes present in the material and also on the shape of the nanoparticles. In the present investigation it was observed that optical absorption increases with increase in particle size. The optical band gap for the Nanoparticles was obtained from plots between hv vs. (αhv){sup 2} and hv vs. (αhv){sup 1/2}. The value of Band gap came out to be around 1.98–2.02 eV which is in close agreement with the earlier reported values.

Random polyfluorene co -polymers designed for a better optical ...

African Journals Online (AJOL)

Two alternating polyfluorenes (APFO15-F8BT and APFO3-F8BT) with full absorption of the visible region of the electromagnetic radiation were designed and synthesized for bulk-heterojunction solar cell devices. The optical and electrochemical properties of the two polymers were studied. The two polymers exhibited strong ...

Handling of bulk solids theory and practice

CERN Document Server

Shamlou, P A

1990-01-01

Handling of Bulk Solids provides a comprehensive discussion of the field of solids flow and handling in the process industries. Presentation of the subject follows classical lines of separate discussions for each topic, so each chapter is self-contained and can be read on its own. Topics discussed include bulk solids flow and handling properties; pressure profiles in bulk solids storage vessels; the design of storage silos for reliable discharge of bulk materials; gravity flow of particulate materials from storage vessels; pneumatic transportation of bulk solids; and the hazards of solid-mater

Nonlinear Optical Properties of Aluminum Doped Zinc Oxide

Science.gov (United States)

Otieno, Calford O.

Nonlinear optical (NLO) materials are crucial to future progress in industrial and technological applications that involve intense light-matter interaction. While ZnO-related materials are known to possess good NLO properties, existing results on ZnO and AZO (Al-doped ZnO) are mostly available at a single wavelength or limited ranges. Therefore, NLO dispersions (wavelength dependences) are not entirely studied, especially at longer wavelengths far below the bandgap. It is important to explore wavelength dependences since doping can induce a drastic change in the NLO responses at varied spectral ranges via doping-induced subgap-state contributions. We present results of our studies on nonlinear harmonic generation from our samples, which include 1) second harmonic generation and 2) third harmonic generation precisely characterized by Maker fringes as a function of both Al doping and wavelength. We exhaustively discuss the possible cause for the modified optical nonlinearities observed in our AZO thin films and give detailed comparisons of our observations with the previous studies. We also present the results of open- and close-aperture Z-scans to characterize the two-photon absorption coefficient (TPA) and the nonlinear refractive index (NLR), respectively, of the AZO films. There was no clearcut evidence of monotonic dependence of TPA and NLR on doping. This presumably indicates that the overall effect is nontrivial and should be understood in terms of combined effects of bandgap shift and crystallinity upon varying the doping level. Most intriguingly, we found that NLR values from the closed-aperture Z-scan are very large by orders of magnitude when compared with the bulk counterparts. Similar observation was made for TPA values from the open-aperture Z-scan. To countercheck very large NLO absorption, we conducted simple intensity scan by varying the incident photon number on each sample but fixing the beam area to eliminate any possible errors related to optical

Preparation and optical and electrical evaluation of bulk SiO{sub 2} sonogel hybrid composites and vacuum thermal evaporated thin films prepared from molecular materials derived from (Fe, Co) metallic phthalocyanines and 1,8 dihydroxiantraquinone compounds

Energy Technology Data Exchange (ETDEWEB)

Sanchez Vergara, Maria Elena [Coordinacion de Ingenieria Mecatronica, Facultad de Ingenieria, Universidad Anahuac Mexico Norte. Avenida Universidad Anahuac 46, Col. Lomas Anahuac, 52786 Huixquilucan, Estado de Mexico (Mexico); Morales-Saavedra, Omar G. [Universidad Nacional Autonoma de Mexico, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, CCADET-UNAM, A.P. 70-186, Coyoacan, 04510 Mexico, D.F. (Mexico)], E-mail: omar.morales@ccadet.unam.mx; Ontiveros-Barrera, Fernando G.; Torres-Zuniga, Vicente; Ortega-Martinez, Roberto [Universidad Nacional Autonoma de Mexico, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, CCADET-UNAM, A.P. 70-186, Coyoacan, 04510 Mexico, D.F. (Mexico); Ortiz Rebollo, Armando [Universidad Nacional Autonoma de Mexico, Instituto de Investigaciones en Materiales, IIM-UNAM, A.P. 70-360, Coyoacan, 04510 Mexico, D.F. (Mexico)

2009-02-25

Semiconducting molecular material of PcFe(CN)L1 and PcCo(CN)L1 (L1 = 1,8 dihydroxianthraquinone), PcFe(CN)L2 and PcCo(CN)L2 (L2 = double potassium salt of 1,8 dihydroxianthraquinone) have been successfully used to prepare thin film and bulk sol-gel hybrid optical materials. These samples were developed according to the vacuum thermal evaporation technique and the catalyst-free sonogel route, respectively. Thin films samples were deposited on Corning glass substrates and crystalline silicon wafers and were characterized by infrared (FTIR), Raman and ultraviolet-visible (UV-vis) spectroscopies. IR-spectroscopy and Raman studies unambiguously confirmed that the molecular material thin films exhibit the same intra-molecular bonds, which suggests that the thermal evaporation process does not alter these bonds significantly. These results show that it is possible to deposit molecular materials of PcFe(CN)L2 and PcCo(CN)L2 on Corning glass substrates and silicon wafers. From the UV-vis studies the optical band gap (E{sub g}) was evaluated. The effect of temperature on conductivity was also evaluated in these samples. Finally, the studied molecular systems dissolved at different concentrations in tetrahydrofuran (THF) were successfully embedded into a highly pure SiO{sub 2} sonogel network generated via sonochemical reactions to form several solid state, optically active sol-gel hybrid glasses. By this method, homogeneous and stable hybrid monoliths suitable for optical characterization can be produced. The linear optical properties of these amorphous bulk structures were determined by the Brewster angle method and by absorption-, Raman- and photoluminescent (PL)-spectroscopies, respectively.

Anomalous optical and electronic properties of dense sodium

International Nuclear Information System (INIS)

Li Dafang; Liu Hanyu; Wang Baotian; Shi Hongliang; Zhu Shaoping; Yan Jun; Zhang Ping

2010-01-01

Based on the density functional theory, we systematically study the optical and electronic properties of the insulating dense sodium phase (Na-hp4) reported recently (Ma et al., 2009). The structure is found optically anisotropic. Through Bader analysis, we conclude that ionicity exists in the structure and becomes stronger with increasing pressure.

THz - ToF Optical Layer Analysis (OLA) to determine optical properties of dielectric materials

Science.gov (United States)

Spranger, Holger; Beckmann, Jörg

2017-02-01

Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. The knowledge of the base materials shape and optical properties is essential for a proper reconstruction result. To obtain these properties a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric characteristics. The Optical Layer Analysis (OLA) is able to fulfill these requirements. A short description why the optical properties are crucial for meaningful SAFT reconstruction results will be given first. Afterwards the OLA will be derived and applied on representative samples to discuss and evaluate its benefits and limits.

Electronic band structure and optical properties of antimony selenide under pressure

Energy Technology Data Exchange (ETDEWEB)

Abhijit, B.K.; Jayaraman, Aditya; Molli, Muralikrishna, E-mail: muralikrishnamolli@sssihl.edu.in [Department of Physics, Sri Sathya Sai Institute of Higher Learning, Prasanthinilayam, 515 134 (India)

2016-05-23

In this work we present the optical properties of Antimony Selenide (Sb{sub 2}Se{sub 3}) under ambient conditions and under pressure of 9.2 GPa obtained using first principles calculations. We investigated the electronic band structure using the FP-LAPW method within the sphere of the density functional theory. Optical properties like refractive index, absorption coefficient and optical conductivity are calculated using the WIEN2k code.

Experimental Investigations of the Physical and Optical Properties of Individual Micron/Submicron-Size Dust Grains in Astrophysical Environments

Science.gov (United States)

Abbas, M. M.; Tankosic, D.; LeClair, A.

2014-01-01

Dust grains constitute a significant component of matter in the universe, and play an important and crucial role in the formation and evolution of the stellar/planetary systems in interstellar dust clouds. Knowledge of physical and optical properties of dust grains is required for understanding of a variety of processes in astrophysical and planetary environments. The currently available and generally employed data on the properties of dust grains is based on bulk materials, with analytical models employed to deduce the corresponding values for individual small micron/submicron-size dust grains. However, it has been well-recognized over a long period, that the properties of individual smallsize dust grains may be very different from those deduced from bulk materials. This has been validated by a series of experimental investigations carried out over the last few years, on a laboratory facility based on an Electrodynamic Balance at NASA, which permits levitation of single small-size dust grains of desired composition and size, in vacuum, in simulated space environments. In this paper, we present a brief review of the results of a series of selected investigations carried out on the analogs of interstellar and planetary dust grains, as well as dust grains obtained by Apollo-l1-17 lunar missions. The selected investigations, with analytical results and discussions, include: (a) Direct measurements of radiation on individual dust grains (b) Rotation and alignments of dust grains by radiative torque (c) Charging properties of dust grains by: (i) UV Photo-electric emissions (ii) Electron Impact. The results from these experiments are examined in the light of the current theories of the processes involved.

Optical properties of gold island films-a spectroscopic ellipsometry study

Energy Technology Data Exchange (ETDEWEB)

Loncaric, Martin, E-mail: mloncaric@irb.hr; Sancho-Parramon, Jordi; Zorc, Hrvoje

2011-02-28

Metal island films of noble metals are obtained by deposition on glass substrates during the first stage of evaporation process when supported metal nanoparticles are formed. These films show unique optical properties, owing to the localized surface plasmon resonance of free electrons in metal nanoparticles. In the present work we study the optical properties of gold metal island films deposited on glass substrates with different mass thicknesses at different substrate temperatures. The optical characterization is performed by spectroscopic ellipsometry at different angles of incidence and transmittance measurements at normal incidence in the same point of the sample. Fitting of the ellipsometric data allows determining the effective optical constants and thickness of the island film. A multiple oscillator approach was used to successfully represent the dispersion of the effective optical constants of the films.

Bulk and surface properties of magnesium peroxide MgO2

Science.gov (United States)

Esch, Tobit R.; Bredow, Thomas

2016-12-01

Magnesium peroxide has been identified in Mg/air batteries as an intermediate in the oxygen reduction reaction (ORR) [1]. It is assumed that MgO2 is involved in the solid-electrolyte interphase on the cathode surface. Therefore its structure and stability play a crucial role in the performance of Mg/air batteries. In this work we present a theoretical study of the bulk and low-index surface properties of MgO2. All methods give a good account of the experimental lattice parameters for MgO2 and MgO bulk. The reaction energies, enthalpies and free energies for MgO2 formation from MgO are compared among the different DFT methods and with the local MP2 method. A pronounced dependence from the applied functional is found. At variance with a previous theoretical study but in agreement with recent experiments we find that the MgO2 formation reaction is endothermic (HSE06-D3BJ: ΔH = 51.9 kJ/mol). The stability of low-index surfaces MgO2 (001) (Es = 0.96 J/m2) and (011) (Es = 1.98 J/m2) is calculated and compared to the surface energy of MgO (001). The formation energy of neutral oxygen vacancies in the topmost layer of the MgO2 (001) surface is calculated and compared with defect formation energies for MgO (001).

Levitation properties of superconducting magnetic bearings using superconducting coils and bulk superconductors

Energy Technology Data Exchange (ETDEWEB)

Arai, Yuuki; Seino, Hiroshi; Nagashima, Ken [Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo 185-8540 (Japan)

2010-11-15

We have been developing a flywheel energy storage system (FESS) with 36 MJ energy capacity for a railway system with superconducting magnetic bearings (SMBs). We prepared two kinds of models using superconducting coils and bulk superconductors (SCs). One model demonstrated SMB load capacity of 20 kN and the other model proved non-contact stable levitation and non-contact rotation with SMBs. Combining these results, the feasibility of a 36 MJ energy capacity FESS with SMBs completely inside a cryostat has been confirmed. In this paper, we report the levitation properties of SMBs in these models.

Levitation properties of superconducting magnetic bearings using superconducting coils and bulk superconductors

International Nuclear Information System (INIS)

Arai, Yuuki; Seino, Hiroshi; Nagashima, Ken

2010-01-01

We have been developing a flywheel energy storage system (FESS) with 36 MJ energy capacity for a railway system with superconducting magnetic bearings (SMBs). We prepared two kinds of models using superconducting coils and bulk superconductors (SCs). One model demonstrated SMB load capacity of 20 kN and the other model proved non-contact stable levitation and non-contact rotation with SMBs. Combining these results, the feasibility of a 36 MJ energy capacity FESS with SMBs completely inside a cryostat has been confirmed. In this paper, we report the levitation properties of SMBs in these models.

The bio-optical properties of CDOM as descriptor of lake stratification.

Science.gov (United States)

Bracchini, Luca; Dattilo, Arduino Massimo; Hull, Vincent; Loiselle, Steven Arthur; Martini, Silvia; Rossi, Claudio; Santinelli, Chiara; Seritti, Alfredo

2006-11-01

Multivariate statistical techniques are used to demonstrate the fundamental role of CDOM optical properties in the description of water masses during the summer stratification of a deep lake. PC1 was linked with dissolved species and PC2 with suspended particles. In the first principal component that the role of CDOM bio-optical properties give a better description of the stratification of the Salto Lake with respect to temperature. The proposed multivariate approach can be used for the analysis of different stratified aquatic ecosystems in relation to interaction between bio-optical properties and stratification of the water body.

On the electronic nature of silicon and germanium based oxynitrides and their related mechanical, optical and vibrational properties as obtained from DFT and DFPT

KAUST Repository

Goumri-Said, Souraya

2012-02-01

Electronic structure, bonding and optical properties of the orthorhombic oxynitrides Si 2N 2O and Ge 2N 2O are studied using the density function theory as implemented in pseudo-potential plane wave and full-potential (linearized) augmented plane wave plus local orbitals methods. Generalized gradient approximation is employed in order to determine the band gap energy. Indeed, the Si 2N 2O exhibits a large direct gap whereas Ge 2N 2O have an indirect one. Bonding is analyzed via the charge densities and Mulliken population, where the role of oxygen is investigated. The analysis of the elastic constants show the mechanical stability of both oxynitrides. Their bulk and shear modulus are slightly smaller than those reported on nitrides semiconductors due to the oxygen presence. The optical properties, namely the dielectric function, optical reflectivity, refractive index and electron energy loss, are reported for radiation up to 30 eV. The phonon dispersion relation, zone-center optical mode frequency, density of phonon states are calculated using the density functional perturbed theory. Thermodynamic properties of Si 2N 2O and Ge 2N 2O, such as heat capacity and Debye temperature, are given for reference. Our study suggests that Si 2N 2O and Ge 2N 2O could be a promising potential materials for applications in the microelectronics and optoelectronics areas of research. © 2011 Elsevier B.V. All rights reserved.

Modelling of bulk superconductor magnetization

International Nuclear Information System (INIS)

Ainslie, M D; Fujishiro, H

2015-01-01

This paper presents a topical review of the current state of the art in modelling the magnetization of bulk superconductors, including both (RE)BCO (where RE = rare earth or Y) and MgB 2 materials. Such modelling is a powerful tool to understand the physical mechanisms of their magnetization, to assist in interpretation of experimental results, and to predict the performance of practical bulk superconductor-based devices, which is particularly important as many superconducting applications head towards the commercialization stage of their development in the coming years. In addition to the analytical and numerical techniques currently used by researchers for modelling such materials, the commonly used practical techniques to magnetize bulk superconductors are summarized with a particular focus on pulsed field magnetization (PFM), which is promising as a compact, mobile and relatively inexpensive magnetizing technique. A number of numerical models developed to analyse the issues related to PFM and optimise the technique are described in detail, including understanding the dynamics of the magnetic flux penetration and the influence of material inhomogeneities, thermal properties, pulse duration, magnitude and shape, and the shape of the magnetization coil(s). The effect of externally applied magnetic fields in different configurations on the attenuation of the trapped field is also discussed. A number of novel and hybrid bulk superconductor structures are described, including improved thermal conductivity structures and ferromagnet–superconductor structures, which have been designed to overcome some of the issues related to bulk superconductors and their magnetization and enhance the intrinsic properties of bulk superconductors acting as trapped field magnets. Finally, the use of hollow bulk cylinders/tubes for shielding is analysed. (topical review)

Thin Film Solar Cells and their Optical Properties

Directory of Open Access Journals (Sweden)

Stanislav Jurecka

2006-01-01

Full Text Available In this work we report on the optical parameters of the semiconductor thin film for solar cell applications determination. The method is based on the dynamical modeling of the spectral reflectance function combined with the stochastic optimization of the initial reflectance model estimation. The spectral dependency of the thin film optical parameters computations is based on the optical transitions modeling. The combination of the dynamical modeling and the stochastic optimization of the initial theoretical model estimation enable comfortable analysis of the spectral dependencies of the optical parameters and incorporation of the microstructure effects on the solar cell properties. The results of the optical parameters ofthe i-a-Si thin film determination are presented.

Realization of an optical interferometer based on holographic optics ...

Indian Academy of Sciences (India)

The paper describes a simple and cost effective method for the realization of an optical interferometer based on holographic optics, which use minimal bulk optical components. The optical arrangement in the proposed method involves a very simple alignment procedure and inexpensive holographic recording material is ...

Quasiparticle and optical properties of strained stanene and stanane.

Science.gov (United States)

Lu, Pengfei; Wu, Liyuan; Yang, Chuanghua; Liang, Dan; Quhe, Ruge; Guan, Pengfei; Wang, Shumin

2017-06-20

Quasiparticle band structures and optical properties of two dimensional stanene and stanane (fully hydrogenated stanene) are studied by the GW and GW plus Bethe-Salpeter equation (GW-BSE) approaches, with inclusion of the spin-orbit coupling (SOC). The SOC effect is significant for the electronic and optical properties in both stanene and stanane, compared with their group IV-enes and IV-anes counterparts. Stanene is a semiconductor with a quasiparticle band gap of 0.10 eV. Stanane has a sizable band gap of 1.63 eV and strongly binding exciton with binding energy of 0.10 eV. Under strain, the quasiparticle band gap and optical spectrum of both stanene and stanane are tunable.

Optical radiative properties of ablating polymers exposed to high-power arc plasmas

Science.gov (United States)

Becerra, Marley; Pettersson, Jonas

2018-03-01

The radiative properties of polymers exposed to high-intensity radiation are of importance for the numerical simulation of arc-induced ablation. The paper investigates the optical properties of polymethylmethacrylate PMMA and polyamide PA6 films exposed to high-power arc plasmas, which can cause ablation of the material. A four-flux radiative approximation is first used to estimate absorption and scattering coefficients of the tested materials in the ultraviolet (UV) and in the visible (VIS) ranges from spectrophotometric measurements. The temperature-induced variation of the collimated transmissivity of the polymers is also measured from room temperature to the glass temperature of PMMA and the melting temperature of PA6. Furthermore, band-averaged absorption and scattering coefficients of non-ablating and ablating polymers are estimated from the UV to the short-wavelength infrared (SWIR), covering the range of interest for the simulation of arc-induced ablation. These estimates are obtained from collimated transmissivities measured with an additional in situ photometric system that uses a high-power, transient arc plasma to both illuminate the samples and to induce ablation. It is shown that the increase in the bulk temperature of PA6 leads to a strong reversible increase in collimated transmissivity, significantly reducing the absorption and scattering coefficients of the material. A weaker but opposite effect of temperature on the optical properties is found in PMMA. As a consequence, it is suggested that the absorption coefficient of polymers used for arc-induced ablation estimates should not be taken directly from direct collimated transmissivity measurements at room temperature. The band-averaged radiation measurements also show that the layer of products released by ablation of PMMA produces scattering radiation losses mainly in the VIS-SWIR ranges, which are only a small fraction of the total incident arc radiation. In a similar manner, the ablation layer

Pressure effect on the structural, elastic, electronic and optical properties of the Zintl phase KAsSn, first principles study

Energy Technology Data Exchange (ETDEWEB)

Guechi, A., E-mail: ab_guechi@yahoo.fr [Institute of Optics and Precision Mechanics, Setif-1 University, 19000 Setif (Algeria); Laboratory of Optoelectronics and Components, Department of Physics, Faculty of Science, Setif-1 University, 19000 Setif (Algeria); Merabet, A. [Institute of Optics and Precision Mechanics, Setif-1 University, 19000 Setif (Algeria); Laboratory of Physics and Mechanics of Metallic Materials, Setif-1 University, 19000 Setif (Algeria); Chegaar, M. [Laboratory of Optoelectronics and Components, Department of Physics, Faculty of Science, Setif-1 University, 19000 Setif (Algeria); Bouhemadou, A. [Laboratory for Developing New Materials and their Characterization, Department of Physics, Faculty of Science, Setif-1 University, 19000 Setif (Algeria); Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Guechi, N. [Laboratory for Developing New Materials and their Characterization, Department of Physics, Faculty of Science, Setif-1 University, 19000 Setif (Algeria)

2015-02-25

Highlights: • KAsSn is interesting in the materials community due to its complex structure and narrow gap. • Physical properties of KAsSn have not taken much attention in previous studies. • The KAsSn structure is shown to be mechanically stable. • KAsSn is predicted to be brittleness and characterized by a weak elastic anisotropy. • Its high absorption in the U.V. energy range shows its use in the optoelectronic devices. - Abstract: In this work, a first-principles study of ternary Zintl phase KAsSn compound using density-functional theory (DFT) method within the generalized gradient approximation developed by Wu–Cohen (GGA-Wc) has been performed. Based on the optimized structural parameter, the electronic structure, elastic and optical properties have been investigated. The calculated lattice constants agree reasonably with the previous results. The effect of high pressure on the structural parameters has been shown. The elastic constants were calculated and satisfy the stability conditions for hexagonal crystal. These indicate that this compound is stable in the studied pressure regime. The single crystal elastic constants (C{sub ij}) and related properties are calculated using the static finite strain technique, moreover the polycrystalline elastic moduli such as bulk modulus, shear modulus, micro-hardness parameter H{sub ν}, Young’s modulus and Poisson’s ratio were estimated using Voigt, Reuss and Hill’s (VRH) approximations. The elastic anisotropy of the KAsSn was also analyzed. On another hand the Debye temperature was obtained from the average sound velocity. Electronic properties have been studied throughout the calculation of band structure, density of states and charge densities. It is shown that this crystal belongs to the semiconductors with a pseudo gap of about 0.34 eV. Furthermore, in order to clarify the optical transitions of this compound, linear optical functions including the complex dielectric function, refractive index

First-principles calculations of bulk and interfacial thermodynamic properties for fcc-based Al-Sc alloys

International Nuclear Information System (INIS)

Asta, M.; Foiles, S.M.; Quong, A.A.

1998-01-01

The configurational thermodynamic properties of fcc-based Al-Sc alloys and coherent Al/Al 3 Sc interphase-boundary interfaces have been calculated from first principles. The computational approach used in this study combines the results of pseudopotential total-energy calculations with a cluster-expansion description of the alloy energetics. Bulk and interface configurational-thermodynamic properties are computed using a low-temperature-expansion technique. Calculated values of the {100} and {111} Al/Al 3 Sc interfacial energies at zero temperature are, respectively, 192 and 226mJ/m 2 . The temperature dependence of the calculated interfacial free energies is found to be very weak for {100} and more appreciable for {111} orientations; the primary effect of configurational disordering at finite temperature is to reduce the degree of crystallographic anisotropy associated with calculated interfacial free energies. The first-principles-computed solid-solubility limits for Sc in bulk fcc Al are found to be underestimated significantly in comparison with experimental measurements. It is argued that this discrepancy can be largely attributed to nonconfigurational contributions to the entropy which have been neglected in the present thermodynamic calculations. copyright 1998 The American Physical Society

Effect of silver addition on the mechanical and field trapping properties of Gd-Ba-Cu-O bulk superconductors

CERN Document Server

Nariki, S; Matsui, M; Murakami, M

2002-01-01

The effect of Ag addition on the microstructure and the mechanical and field trapping properties of Gd-Ba-Cu-O bulk superconductor has been investigated. The single grain Gd-Ba-Cu-O bulk superconductors 32 mm in diameter were fabricated with 0-30 mass%Ag/sub 2/O additions by the melt growth method under controlled oxygen partial pressure of 1.0%. From microscopic observations, it was found that the macro- cracks in the a-b plane decreased with Ag addition. The three-point bending test showed that the average strength of Ag-free bulk was 69 MPa at room temperature, while the strength was dramatically improved to 110-115 MPa with 10-30 mass%Ag/sub 2/O additions. The trapped magnetic field of Ag-free bulk sample was 1.3 T at 77 K. The trapped field of bulk Gd-Ba-Cu-O samples with 10-20 mass%Ag/sub 2/O exhibited high values of 1.8-2.0 T at 77 K. However, the trapped field of the sample with 30 mass%Ag/sub 2/O addition was lowered to 1.1 T with decreasing the critical current density. The trapped field of Ag- adde...

Complex yet translucent: the optical properties of sea ice

International Nuclear Information System (INIS)

Perovich, Donald K.

2003-01-01

Sea ice is a naturally occurring material with an intricate and highly variable structure consisting of ice platelets, brine pockets, air bubbles, and precipitated salt crystals. The optical properties of sea ice are directly dependent on this ice structure. Because sea ice is a material that exists at its salinity determined freezing point, its structure and optical properties are significantly affected by small changes in temperature. Understanding the interaction of sunlight with sea ice is important to a diverse array of scientific problems, including those in polar climatology. A key optical parameter for climatological studies is the albedo, the fraction of the incident sunlight that is reflected. The albedo of sea ice is quite sensitive to surface conditions. The presence of a snow cover enhances the albedo, while surface meltwater reduces the albedo. Radiative transfer in sea ice is a combination of absorption and scattering. Differences in the magnitude of sea ice optical properties are ascribable primarily to differences in scattering, while spectral variations are mainly a result of absorption. Physical changes that enhance scattering, such as the formation of air bubbles due to brine drainage, result in more light reflection and less transmission

Optical properties of quasiperiodically arranged semiconductor nanostructures

Energy Technology Data Exchange (ETDEWEB)

Werchner, Marco

2009-12-18

This work consists of two parts which are entitled ''One-Dimensional Resonant Fibonacci Quasicrystals'' and ''Resonant Tunneling of Light in Silicon Nanostructures''. A microscopic theory has been applied to investigate the optical properties of the respective semiconductor nanostructures. The studied one-dimensional resonant Fibonacci quasicrystals consist of GaAs quantum wells (QW) that are separated by either a large spacer L or a small one S. These spacers are arranged according to the Fibonacci sequence LSLLSLSL.. The average spacing satisfies a generalized Bragg condition with respect to the 1s-exciton resonance of the QWs. A theory, that makes use of the transfer-matrix method and that allows for the microscopic description of many-body effects such as excitation-induced dephasing caused by the Coulomb scattering of carriers, has been applied to compute the optical spectra of such structures. A pronounced sharp reflectivity minimum is found in the vicinity of the heavy-hole resonance both in the measured as well as in the calculated linear 54-QW spectra. Specifically, the influence of the carrier density, of the QW arrangement, of a detuning away from the exact Bragg condition, of the average spacing as well as of the ratio of the optical path lengths of the large and small spacers L and S, respectively, and of the QW number on the optical properties of the samples have been studied. Additionally, self-similarity among reflection spectra corresponding to different QW numbers that exceed a Fibonacci number by one is observed, which identifies certain spectral features as true fingerprints of the Fibonacci spacing. In the second part, resonant tunneling of light in stacked structures consisting of alternating parallel layers of silicon and air have been studied theoretically.Light may tunnel through the air barrier due to the existence of evanescent waves inside the air layers if the neighboring silicon layer is close

First-principles calculations of the structural, electronic and optical properties of cubic B{sub x}Ga{sub 1-x}As alloys

Energy Technology Data Exchange (ETDEWEB)

Guemou, M., E-mail: guemoumhamed7@gmail.com [Engineering Physics Laboratory, University Ibn Khaldoun of Tiaret, BP 78-Zaaroura, Tiaret 14000 (Algeria); Bouhafs, B. [Modelling and Simulation in Materials Science Laboratory, Physics Department, University of Sidi Bel-Abbes, 22000 Sidi Bel-Abbes (Algeria); Abdiche, A. [Applied Materials Laboratory, Research Center, University of Sidi Bel Abbes, 22000 Sidi Bel Abbes (Algeria); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Departement de Technologie, Universite de Mascara, 29000 Mascara (Algeria); Al Douri, Y. [Institute of Nano Electronic Engineering, Universiti Malaysia Perlis, Perlis (Malaysia); Bin Omran, S. [Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia)

2012-04-15

Density functional calculations are performed to study the structural, electronic and optical properties of technologically important B{sub x}Ga{sub 1-x}As ternary alloys. The calculations are based on the total-energy calculations within the full-potential augmented plane-wave (FP-LAPW) method. For exchange-correlation potential, local density approximation (LDA) and the generalized gradient approximation (GGA) have been used. The structural properties, including lattice constants, bulk modulus and their pressure derivatives, are in very good agreement with the available experimental and theoretical data. The electronic band structure, density of states for the binary compounds and their ternary alloys are given. The dielectric function and the refractive index are also calculated using different models. The obtained results compare very well with previous calculations and experimental measurements.

Process parameters, orientation, and functional properties of melt-processed bulk Y-Ba-Cu-O superconductors

International Nuclear Information System (INIS)

Zakharchenko, I.V.; Terryll, K.M.; Rao, K.V.; Balachandran, U.

1995-03-01

This study compared the microstructure, texturing, and functional properties (critical currents) of YBa 2 Cu 3 O 7-x -based bulk pellets that were prepared by the quench-melt-growth-process (QMGP), melt-textured growth (MTG), and conventional solid-state reaction (SSR) approaches. Using two X-ray diffraction (XRD) methods, θ-2θ, and rocking curves, the authors found that the individual grains of two melt-processed pellets exhibited remarkable preferred orientational alignment (best rocking curve width = 3.2 degree). However, the direction of the preferred orientation among the grains was random. Among the three types of bulk materials studied, the QMGP sample was found to have the best J c values, ∼ 4,500 A/cm 2 at 77 K in a field of 2 kG, as determined from SQUID magnetic data

A novel method of rapidly modeling optical properties of actual photonic crystal fibres

International Nuclear Information System (INIS)

Li-Wen, Wang; Shu-Qin, Lou; Wei-Guo, Chen; Hong-Lei, Li

2010-01-01

The flexible structure of photonic crystal fibre not only offers novel optical properties but also brings some difficulties in keeping the fibre structure in the fabrication process which inevitably cause the optical properties of the resulting fibre to deviate from the designed properties. Therefore, a method of evaluating the optical properties of the actual fibre is necessary for the purpose of application. Up to now, the methods employed to measure the properties of the actual photonic crystal fibre often require long fibre samples or complex expensive equipments. To our knowledge, there are few studies of modeling an actual photonic crystal fibre and evaluating its properties rapidly. In this paper, a novel method, based on the combination model of digital image processing and the finite element method, is proposed to rapidly model the optical properties of the actual photonic crystal fibre. Two kinds of photonic crystal fibres made by Crystal Fiber A/S are modeled. It is confirmed from numerical results that the proposed method is simple, rapid and accurate for evaluating the optical properties of the actual photonic crystal fibre without requiring complex equipment. (rapid communication)

Field investigations of apparent optical properties of ice cover in Finnish and Estonian lakes in winter 2009

Directory of Open Access Journals (Sweden)

Ruibo Lei

2011-03-01

Full Text Available A field programme on light conditions in ice-covered lakes and optical properties of lake ice was performed in seven lakes of Finland and Estonia in February–April 2009. On the basis of irradiance measurements above and below ice, spectral reflectance and transmittance were determined for the ice sheet; time evolution of photosynthetically active radiation (PAR transmittance was examined from irradiance recordings at several levels inside the ice sheet. Snow cover was the dominant factor for transmission of PAR into the lake water body. Reflectance was 0.74–0.92 in winter, going down to 0.18–0.22 in the melting season. The bulk attenuation coefficient of dry snow was 14–25 m–1; the level decreased as the spring was coming. The reflectance and bulk attenuation coefficient of snow-free ice were 0.1–0.4 and 1–5 m–1. Both were considerably smaller than those of snow cover. Seasonal evolution of light transmission was mainly due to snow melting. Snow and ice cover not only depress the PAR level in a lake but also influence the spectral and directional distribution of light.

Bulk metallic glass matrix composites

International Nuclear Information System (INIS)

Choi-Yim, H.; Johnson, W.L.

1997-01-01

Composites with a bulk metallic glass matrix were synthesized and characterized. This was made possible by the recent development of bulk metallic glasses that exhibit high resistance to crystallization in the undercooled liquid state. In this letter, experimental methods for processing metallic glass composites are introduced. Three different bulk metallic glass forming alloys were used as the matrix materials. Both ceramics and metals were introduced as reinforcement into the metallic glass. The metallic glass matrix remained amorphous after adding up to a 30 vol% fraction of particles or short wires. X-ray diffraction patterns of the composites show only peaks from the second phase particles superimposed on the broad diffuse maxima from the amorphous phase. Optical micrographs reveal uniformly distributed particles in the matrix. The glass transition of the amorphous matrix and the crystallization behavior of the composites were studied by calorimetric methods. copyright 1997 American Institute of Physics

Electronic and optical properties of diamond/organic semiconductor heterostructures

Energy Technology Data Exchange (ETDEWEB)

Gajewski, Wojciech; Garrido, Jose; Niedermeier, Martin; Stutzmann, Martin [Walter Schottky Institute, TU Muenchen, Am Coulombwall 3, 85748 Garching (Germany); Williams, Oliver; Haenen, Ken [Institute for Materials Research, University of Hasselt, Wetenschapspark 1, BE-3590 Diepenbeek (Belgium)

2007-07-01

Different diamond substrates (single crystalline: SCD, poly-crystalline: PCD and nano-crystalline: NCD) were used to investigate the electronic and optical properties of the diamond/organic semiconductor heterostructures. Layers of a poly[ethynyl-(2-decyloxy-5methoxy)benzene] - PEB, pentacene and 4-nitro-biphenyl-4-diazonium cations - Ph-Ph-NO{sub 2} were prepared by spin coating, thermal evaporation and grafting, respectively. The measurements of the electronic transport along the organic layer were performed using a Hg probe as well as Hall effect measurements in the temperature range 70-400 K. The I-V characteristics of the B-doped diamond/organic semiconductor heterostructures were measured at room temperature by means of the Hg probe. Undoped IIa and undoped PCD films were used for a study of the optical and optoelectronic properties of prepared heterostructures. The influence of the organic layer homogeneity and layer thickness on the optical properties will be discussed. Furthermore, preliminary data on perpendicular and parallel transport in the heterostructures layer will be reported.

Optical Properties and Immunoassay Applications of Noble Metal Nanoparticles

International Nuclear Information System (INIS)

Zhu, S.; Zhou, W.

2010-01-01

Noble metal, especially gold (Au) and silver (Ag) nanoparticles exhibit unique and tunable optical properties on account of their surface plasmon resonance (SPR). In this paper, we mainly discussed the theory background of the enhanced optical properties of noble metal nanoparticles. Mie theory, transfer matrix method, discrete dipole approximation (DDA) method, and finite-difference time domain (FDTD) method applied brute-force computational methods for different nanoparticles optical properties. Some important nanostructure fabrication technologies such as nanosphere lithography (NSL) and focused ion beam (FIB) are also introduced in this paper. Moreover, these fabricated nanostructures are used in the plasmonic sensing fields. The binding signal between the antibody and antigen, amyloid-derived diffusible ligands (ADDLs)-potential Alzheimer's disease (AD) biomarkers, and staphylococcal enterotoxin B (SEB) in nano-Moore per liter (nM) concentration level are detected by our designed nanobiosensor. They have many potential applications in the biosensor, environment protection, food security, and medicine safety for health, and so forth, fields.

Optical Properties and Immunoassay Applications of Noble Metal Nanoparticles

Directory of Open Access Journals (Sweden)

Shaoli Zhu

2010-01-01

Full Text Available Noble metal, especially gold (Au and silver (Ag nanoparticles exhibit unique and tunable optical properties on account of their surface plasmon resonance (SPR. In this paper, we mainly discussed the theory background of the enhanced optical properties of noble metal nanoparticles. Mie theory, transfer matrix method, discrete dipole approximation (DDA method, and finite-difference time domain (FDTD method applied brute-force computational methods for different nanoparticles optical properties. Some important nanostructure fabrication technologies such as nanosphere lithography (NSL and focused ion beam (FIB are also introduced in this paper. Moreover, these fabricated nanostructures are used in the plasmonic sensing fields. The binding signal between the antibody and antigen, amyloid-derived diffusible ligands (ADDLs-potential Alzheimer's disease (AD biomarkers, and staphylococcal enterotixn B (SEB in nano-Moore per liter (nM concentration level are detected by our designed nanobiosensor. They have many potential applications in the biosensor, environment protection, food security, and medicine safety for health, and so forth, fields.

Investigation of structural, electronic, elastic and optical properties of Cd{sub 1-x-y}Zn{sub x}Hg{sub y}Te alloys

Energy Technology Data Exchange (ETDEWEB)

Tamer, M., E-mail: mehmet.tamer@zirve.edu.tr [Zirve University Faculty of Education, 27260, Gaziantep (Turkey)

2016-06-15

Structural, optical and electronic properties and elastic constants of Cd1{sub -x-y}Zn{sub x} Hg{sub y}Te alloys have been studied by employing the commercial code Castep based on density functional theory. The generalized gradient approximation and local density approximation were utilized as exchange correlation. Using elastic constants for compounds, bulk modulus, band gap, Fermi energy and Kramers–Kronig relations, dielectric constants and the refractive index have been found through calculations. Apart from these, X-ray measurements revealed elastic constants and Vegard’s law. It is seen that results obtained from theory and experiments are all in agreement.

Terahertz electromagnetic response and its electric field manipulation of bulked silicene

International Nuclear Information System (INIS)

Bao, Hairui; Liao, Wenhu; Guo, Junji; Zhao, Heping; Zhou, Guanghui

2015-01-01

We theoretically investigate the infrared optical properties of a three-terminal silicene-based device under the irradiation of a circularly polarized terahertz (THz) electromagnetic field, utilizing the intersubband transition theorem at low temperatures. It has been demonstrated that the electronic structure of bulked silicene can be tuned to the topological insulated (TI) and band insulated (BI) state, respectively, via the back-gate voltage induced staggered sublattice potential. Furthermore, with the enhancement of the staggered sublattice potential, the refractive index, extinction coefficient and optical conductivity from the TI state spin-up and -down subbands are observed to be red- and blue-shifted, respectively, while those from the BI state spin-up and -down subbands are proved to be continually blue-shifted. The collective excitations and individual electron–hole pair excitations induced a TI and BI state electron energy loss spectrum (EELS) with a similar red- and/or blue-shift behaviour as the refractive index, extinction coefficient and optical conductivity. The obtained results may be useful in the design of the spintronic and optoelectronic devices based on silicene. (letter)

Intra-connected three-dimensionally isotropic bulk negative index photonic metamaterial

International Nuclear Information System (INIS)

Guney, Durdu; Koschny, Thomas; Soukoulis, Costas

2010-01-01

Isotropic negative index metamaterials (NIMs) are highly desired, particularly for the realization of ultra-high resolution lenses. However, existing isotropic NIMs function only two-dimensionally and cannot be miniaturized beyond microwaves. Direct laser writing processes can be a paradigm shift toward the fabrication of three-dimensionally (3D) isotropic bulk optical metamaterials, but only at the expense of an additional design constraint, namely connectivity. Here, we demonstrate with a proof-of-principle design that the requirement connectivity does not preclude fully isotropic left-handed behavior. This is an important step towards the realization of bulk 3D isotropic NIMs at optical wavelengths.

Some properties of point processes in statistical optics

International Nuclear Information System (INIS)

Picinbono, B.; Bendjaballah, C.

2010-01-01

The analysis of the statistical properties of the point process (PP) of photon detection times can be used to determine whether or not an optical field is classical, in the sense that its statistical description does not require the methods of quantum optics. This determination is, however, more difficult than ordinarily admitted and the first aim of this paper is to illustrate this point by using some results of the PP theory. For example, it is well known that the analysis of the photodetection of classical fields exhibits the so-called bunching effect. But this property alone cannot be used to decide the nature of a given optical field. Indeed, we have presented examples of point processes for which a bunching effect appears and yet they cannot be obtained from a classical field. These examples are illustrated by computer simulations. Similarly, it is often admitted that for fields with very low light intensity the bunching or antibunching can be described by using the statistical properties of the distance between successive events of the point process, which simplifies the experimental procedure. We have shown that, while this property is valid for classical PPs, it has no reason to be true for nonclassical PPs, and we have presented some examples of this situation also illustrated by computer simulations.

Bulk properties and near-critical behaviour of SiO2 fluid

Science.gov (United States)

Green, Eleanor C. R.; Artacho, Emilio; Connolly, James A. D.

2018-06-01

Rocky planets and satellites form through impact and accretion processes that often involve silicate fluids at extreme temperatures. First-principles molecular dynamics (FPMD) simulations have been used to investigate the bulk thermodynamic properties of SiO2 fluid at high temperatures (4000-6000 K) and low densities (500-2240 kg m-3), conditions which are relevant to protoplanetary disc condensation. Liquid SiO2 is highly networked at the upper end of this density range, but depolymerises with increasing temperature and volume, in a process characterised by the formation of oxygen-oxygen (Odbnd O) pairs. The onset of vaporisation is closely associated with the depolymerisation process, and is likely to be non-stoichiometric at high temperature, initiated via the exsolution of O2 molecules to leave a Si-enriched fluid. By 6000 K the simulated fluid is supercritical. A large anomaly in the constant-volume heat capacity occurs near the critical temperature. We present tabulated thermodynamic properties for silica fluid that reconcile observations from FPMD simulations with current knowledge of the SiO2 melting curve and experimental Hugoniot curves.

Optical Properties of Semiconductor Quantum Dots

NARCIS (Netherlands)

Perinetti, U.

2011-01-01

This thesis presents different optical experiments performed on semiconductor quantum dots. These structures allow to confine a small number of electrons and holes to a tiny region of space, some nm across. The aim of this work was to study the basic properties of different types of quantum dots

Optical properties of photoreceptor and retinal pigment epithelium cells investigated with adaptive optics optical coherence tomography

Science.gov (United States)

Liu, Zhuolin

Human vision starts when photoreceptors collect and respond to light. Photoreceptors do not function in isolation though, but share close interdependence with neighboring photoreceptors and underlying retinal pigment epithelium (RPE) cells. These cellular interactions are essential for normal function of the photoreceptor-RPE complex, but methods to assess these in the living human eye are limited. One approach that has gained increased promise is high-resolution retinal imaging that has undergone tremendous technological advances over the last two decades to probe the living retina at the cellular level. Pivotal in these advances has been adaptive optics (AO) and optical coherence tomography (OCT) that together allow unprecedented spatial resolution of retinal structures in all three dimensions. Using these high-resolution systems, cone photoreceptor are now routinely imaged in healthy and diseased retina enabling fundamental structural properties of cones to be studied such as cell spacing, packing arrangement, and alignment. Other important cell properties, however, have remained elusive to investigation as even better imaging performance is required and thus has resulted in an incomplete understanding of how cells in the photoreceptor-RPE complex interact with light. To address this technical bottleneck, we expanded the imaging capability of AO-OCT to detect and quantify more accurately and completely the optical properties of cone photoreceptor and RPE cells at the cellular level in the living human retina. The first objective of this thesis was development of a new AO-OCT method that is more precise and sensitive, thus enabling a more detailed view of the 3D optical signature of the photoreceptor-RPE complex than was previously possible (Chapter 2). Using this new system, the second objective was quantifying the waveguide properties of individual cone photoreceptor inner and outer segments across the macula (Chapter 3). The third objective extended the AO

Optical properties of alkaline earth borate glasses

African Journals Online (AJOL)

user

... devices; radiation shields, surgical lasers and their glass ceramic counter ... Alkaline earth oxides improve glass forming capability while heavy metal ... reports on optical properties of MO-B2O3 glasses containing alkaline earth oxides.

Nanoparticles in Polymers: Assembly, Rheology and Properties

Science.gov (United States)

Rao, Yuanqiao

Inorganic nanoparticles have the potential of providing functionalities that are difficult to realize using organic materials; and nanocomposites is an effective mean to impart processibility and construct bulk materials with breakthrough properties. The dispersion and assembly of nanoparticles are critical to both processibility and properties of the resulting product. In this talk, we will discuss several methods to control the hierarchical structure of nanoparticles in polymers and resulting rheological, mechanical and optical properties. In one example, polymer-particle interaction and secondary microstructure were designed to provide a low viscosity composition comprising exfoliated high aspect ratio clay nanoparticles; in another example, the microstructure control through templates was shown to enable unique thermal mechanical and optical properties. Jeff Munro, Stephanie Potisek, Phillip Hustad; all of the Dow Chemical Company are co-authors.

Electronic Structure and Optical Properties Of EuIn2P2

KAUST Repository

Singh, Nirpendra

2011-10-25

The electronic structures and, optical and magneto‐optical properties of a newly found Zintl compound EuIn2P2 have been investigated within the density‐functional theory using the highly precise full‐potential linear‐augmented‐plane‐wave method. Results of detailed investigation of the electronic structure and related properties are reported.

Ultradense, Deep Subwavelength Nanowire Array Photovoltaics As Engineered Optical Thin Films

KAUST Repository

Tham, Douglas

2010-11-10

A photovoltaic device comprised of an array of 20 nm wide, 32 nm pitch array of silicon nanowires is modeled as an optical material. The nanowire array (NWA) has characteristic device features that are deep in the subwavelength regime for light, which permits a number of simplifying approximations. Using photocurrent measurements as a probe of the absorptance, we show that the NWA optical properties can be accurately modeled with rigorous coupled-wave analysis. The densely structured NWAs behave as homogeneous birefringent materials into the ultraviolet with effective optical properties that are accurately modeled using the dielectric functions of bulk Si and SiO 2, coupled with a physical model for the NWA derived from ellipsometry and transmission electron microscopy. © 2010 American Chemical Society.

Metallic nanoshells with semiconductor cores: optical characteristics modified by core medium properties.

Science.gov (United States)

Bardhan, Rizia; Grady, Nathaniel K; Ali, Tamer; Halas, Naomi J

2010-10-26

It is well-known that the geometry of a nanoshell controls the resonance frequencies of its plasmon modes; however, the properties of the core material also strongly influence its optical properties. Here we report the synthesis of Au nanoshells with semiconductor cores of cuprous oxide and examine their optical characteristics. This material system allows us to systematically examine the role of core material on nanoshell optical properties, comparing Cu(2)O core nanoshells (ε(c) ∼ 7) to lower core dielectric constant SiO(2) core nanoshells (ε(c) = 2) and higher dielectric constant mixed valency iron oxide nanoshells (ε(c) = 12). Increasing the core dielectric constant increases nanoparticle absorption efficiency, reduces plasmon line width, and modifies plasmon energies. Modifying the core medium provides an additional means of tailoring both the near- and far-field optical properties in this unique nanoparticle system.

Unraveling the size-dependent optical properties of dissolved organic matter

DEFF Research Database (Denmark)

Wünsch, Urban; Stedmon, Colin; Tranvik, Lars

2018-01-01

The size-dependent optical properties of dissolved organic matter (DOM) from four Swedish lakes were investigated using High Performance Size Exclusion Chromatography (HPSEC) in conjunction with online characterization of absorbance (240–600 nm) and fluorescence (excitation: 275 nm, emission: 300....... This study demonstrates the potential for HPSEC and novel mathematical approaches to provide unprecedented insights into the relationship between optical and chemical properties of DOM in aquatic systems...

Effect of solvent medium on the structural, morphological and optical properties of ZnS nanoparticles synthesized by solvothermal route

Energy Technology Data Exchange (ETDEWEB)

Mendil, R., E-mail: radia.mendil@yahoo.fr [Laboratoire de Physique des Matériaux et des Nanomatériaux appliquée à l' Environnement, Université de Gabès, Faculté des Sciences de Gabès, Cité Erriadh Manara Zrig, 6072 Gabès (Tunisia); Ben Ayadi, Z. [Laboratoire de Physique des Matériaux et des Nanomatériaux appliquée à l' Environnement, Université de Gabès, Faculté des Sciences de Gabès, Cité Erriadh Manara Zrig, 6072 Gabès (Tunisia); Djessas, K. [Laboratoire Procédés, Matériaux et Energie Solaire (PROMES-CNRS), TECNOSUD, Rambla de la thermodynamique, 66100 Perpignan (France); Université de Perpignan Via Domitia, 52 avenue Paul Alduy, 68860, Perpignan Cedex9 (France)

2016-09-05

Different morphologies of ZnS have been synthesized by a facile solvothermal approach in a mixed solvent made of Ethylenediamine (EN) and distilled water. The effect of solvent medium on the structural, morphological and optical properties of ZnS nanoparticles were investigated. The formation mechanism of different morphologies was proposed based on the experiment results. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), Raman spectroscopy and UV-Vis-IR spectrophotometer. The results show that phase transformation is easily induced and there is a strong correlation between morphology and structure of the ZnS nanocrystals by changing the solvent. The results also show that we have successfully produced hexagonal phase ZnS nanorods with mixed solvent. The grain sizes in the range of 17–22 nm were obtained according to elaboration conditions. Raman spectra show the intense peak at 346 cm{sup −1}, which is a typical Raman peak of bulk ZnS crystal, no signature of secondary phases. The band gap of ZnS increased from 3.49 to 3.74 eV with an increase in the EN composition in the solvent, implying that the optical properties of these materials are clearly affected by the synthesis medium. - Highlights: • ZnS was prepared at low temperature using solvothermal method. • The phase transformation and shape evolution processes were studied. • The role of solvent (EN/W) has been discussed for formation of ZnS nanostructures with different morphology. • The properties and growth mechanism of ZnS nanoparticles were investigated. • Optical band gap of ZnS powder were investigated using UV vis spectroscopy.

Fission fragment simulation of fusion neutron radiation effects on bulk mechanical properties

International Nuclear Information System (INIS)

Van Konynenburg, R.A.; Mitchell, J.B.; Guinan, M.W.; Stuart, R.N.; Borg, R.J.

1976-01-01

This research demonstrates the feasibility of using homogeneously-generated fission fragments to simulate high-fluence fusion neutron damage in niobium tensile specimens. This technique makes it possible to measure radiation effects on bulk mechanical properties at high damage states, using conveniently short irradiation times. The primary knock-on spectrum for a fusion reactor is very similar to that produced by fission fragments, and nearly the same ratio of gas atoms to displaced atoms is produced in niobium. The damage from fission fragments is compared to that from fusion neutrons and fission reactor neutrons in terms of experimentally measured yield strength increase, transmission electron microscopy (TEM) observations, and calculated damage energies

Optical and Electrical Properties of Ar+ Implanted PET

Science.gov (United States)

Kumar, Rajiv; Shekhawat, Nidhi; Sharma, Annu; Aggarwal, Sanjeev; Kumar, Praveen; Kanjilal, D.

2011-07-01

In the present work, the effect of 100 keV argon ion implantation on the optical and electrical properties of PET has been studied. A continuous reduction in optical band gap (from 3.63 to 1.93 eV) with increasing implantation dose has been observed as analyzed using UV-Visible absorption spectroscopy. Current-Voltage (I-V) characteristics have been studied which clearly indicate the enhancement in the conductivity of PET specimens as an effect of implantation. This increase in conductivity has been correlated with the decrease in optical band gap.

Far-infrared properties of optically selected quasars

International Nuclear Information System (INIS)

Edelson, R.A.

1986-01-01

The far-infrared properties of 10, optically selected quasars were studied on the basis of pointed IRAS observations and ground-based near-infrared and radio measurements. Nine of these quasars were detected in at least three IRAS bands. The flat spectral energy distributions characterizing these optically selected quasars together with large 60-100-micron luminosities suggest that the infrared emission is dominated by nonthermal radiation. Seven of the nine quasars with far-infrared detections were found to have low-frequency turnovers. 12 references

Integrating sphere-based setup as an accurate system for optical properties measurements

CSIR Research Space (South Africa)

Abdalmonem, S

2010-09-01

Full Text Available Determination of the optical properties of solid and liquid samples has great importance. Since the integrating sphere-based setup is used to measure the amount of reflected and transmitted light by the examined samples, optical properties could...

The study of structural, elastic, electronic and optical properties of CsYx I(1 − x(Y = F, Cl, Br using density functional theory

Directory of Open Access Journals (Sweden)

Mian Shabeer Ahmad

2017-04-01

Full Text Available The structural, electronic, elastic and optical properties of CsYx I(1 − x(Y = F, Cl, Br are investigated using full potential linearized augmented plane wave (FP-LAPW method within the generalized gradient approximation (GGA. The ground state properties such as lattice constant (ao and bulk modulus (K have been calculated. The mechanical properties including Poisson’s ratio (σ, Young’s modulus (E, anisotropy factor (A and shear modulus (G were also calculated. The results of these calculations are comparable with the reported experimental and theoretical values. The ductility of CsYx I(1 − x was analyzed using Pugh’s rule (B/G ratio and Cauchy’s pressure (C12−C44. Our results revealed that CsF is the most ductile among the CsYxI(1 − x(Y = F, Cl, Br compounds. The incremental addition of lighter halogens (Yx slightly weakens the strength of ionic bond in CsYxI(1 − x. Moreover, the optical transitions were found to be direct for binary and ternary CsYxI(1 − x. We hope that this study will be helpful in designing binary and ternary Cs halides for optoelectronic applications.

Theoretical optical spectroscopy of complex systems

Energy Technology Data Exchange (ETDEWEB)

Conte, A. Mosca, E-mail: adriano.mosca.conte@roma2.infn.it [MIFP, NAST, ETSF,CNR INFM-SMC, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, Roma (Italy); Violante, C., E-mail: claudia.violante@roma2.infn.it [MIFP, NAST, ETSF,CNR INFM-SMC, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, Roma (Italy); Missori, M., E-mail: mauro.missori@isc.cnr.it [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Via Salaria Km 29.300, 00016 Monterotondo Scalo (Rome) (Italy); Bechstedt, F., E-mail: bech@ifto.physik.uni-jena.de [Institut fur Festkorpertheorie und -optik, Friedrich-Schiller-Universitat, Max-Wien-Platz 1, 07743 Jena (Germany); Teodonio, L. [MIFP, NAST, ETSF,CNR INFM-SMC, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, Roma (Italy); Istituto centrale per il restauro e la conservazione del patrimonio archivistico e librario (IC-RCPAL), Italian Minister for Cultural Heritage, Via Milano 76, 00184 Rome (Italy); Ippoliti, E.; Carloni, P. [German Research School for Simulation Sciences, Julich (Germany); Guidoni, L., E-mail: leonardo.guidoni@univaq.it [Università degli Studi di L’Aquila, Dipartimento di Chimica e Materiali, Via Campo di Pile, 67100 L’Aquila (Italy); Pulci, O., E-mail: olivia.pulci@roma2.infn.it [MIFP, NAST, ETSF,CNR INFM-SMC, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, Roma (Italy)

2013-08-15

Highlights: ► We review some theoretical condensed matter ab initio spectroscopic computational techniques. ► We show several applications ranging from 0 to 3 dimensional systems. ► For each system studied, we show which kind of information it is possible to obtain by performing these calculations. -- Abstract: We review here some of the most reliable and efficient computational theoretical ab initio techniques for the prediction of optical and electronic spectroscopic properties and show some important applications to molecules, surfaces, and solids. We investigate the role of the solvent in the optical absorption spectrum of indole molecule. We study the excited-state properties of a photo-active minimal model molecule for the retinal of rhodopsin, responsible for vision mechanism in animals. We then show a study about spectroscopic properties of Si(1 1 1) surface. Finally we simulate a bulk system: paper, that is mainly made of cellulose, a pseudo-crystalline material representing 40% of annual biomass production in the Earth.

Theoretical optical spectroscopy of complex systems

International Nuclear Information System (INIS)

Conte, A. Mosca; Violante, C.; Missori, M.; Bechstedt, F.; Teodonio, L.; Ippoliti, E.; Carloni, P.; Guidoni, L.; Pulci, O.

2013-01-01

Highlights: ► We review some theoretical condensed matter ab initio spectroscopic computational techniques. ► We show several applications ranging from 0 to 3 dimensional systems. ► For each system studied, we show which kind of information it is possible to obtain by performing these calculations. -- Abstract: We review here some of the most reliable and efficient computational theoretical ab initio techniques for the prediction of optical and electronic spectroscopic properties and show some important applications to molecules, surfaces, and solids. We investigate the role of the solvent in the optical absorption spectrum of indole molecule. We study the excited-state properties of a photo-active minimal model molecule for the retinal of rhodopsin, responsible for vision mechanism in animals. We then show a study about spectroscopic properties of Si(1 1 1) surface. Finally we simulate a bulk system: paper, that is mainly made of cellulose, a pseudo-crystalline material representing 40% of annual biomass production in the Earth

Relevant optical properties for direct restorative materials.

Science.gov (United States)

Pecho, Oscar E; Ghinea, Razvan; do Amaral, Erika A Navarro; Cardona, Juan C; Della Bona, Alvaro; Pérez, María M

2016-05-01

To evaluate relevant optical properties of esthetic direct restorative materials focusing on whitened and translucent shades. Enamel (E), body (B), dentin (D), translucent (T) and whitened (Wh) shades for E (WhE) and B (WhB) from a restorative system (Filtek Supreme XTE, 3M ESPE) were evaluated. Samples (1 mm thick) were prepared. Spectral reflectance (R%) and color coordinates (L*, a*, b*, C* and h°) were measured against black and white backgrounds, using a spectroradiometer, in a viewing booth, with CIE D65 illuminant and d/0° geometry. Scattering (S) and absorption (K) coefficients and transmittance (T%) were calculated using Kubelka-Munk's equations. Translucency (TP) and opalescence (OP) parameters and whiteness index (W*) were obtained from differences of CIELAB color coordinates. R%, S, K and T% curves from all shades were compared using VAF (Variance Accounting For) coefficient with Cauchy-Schwarz inequality. Color coordinates and optical parameters were statistically analyzed using one-way ANOVA, Tukey's test with Bonferroni correction (α=0.0007). Spectral behavior of R% and S were different for T shades. In addition, T shades showed the lowest R%, S and K values, as well as the highest T%, TP an OP values. In most cases, WhB shades showed different color and optical properties (including TP and W*) than their corresponding B shades. WhE shades showed similar mean W* values and higher mean T% and TP values than E shades. When using whitened or translucent composites, the final color is influenced not only by the intraoral background but also by the color and optical properties of multilayers used in the esthetic restoration. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Optical properties of a multibarrier structure under intense laser fields

Science.gov (United States)

Ospina, D. A.; Akimov, V.; Mora-Ramos, M. E.; Morales, A. L.; Tulupenko, V.; Duque, C. A.

2015-11-01

Using the diagonalization method and within the effective mass and parabolic band approximations, the energy spectrum and the wave functions are investigated in biased multibarrier structure taking into account the effects of nonresonant intense laser fields. We calculated the optical properties from the susceptibility using a nonperturbative formalism recently reported. We study the changes in the intersubband optical absorption coefficients and refraction index for several values of the dressing laser parameter and for some specific values of the electric field applied along the growth direction of the heterostructure. It is concluded from our study that the peaks in the optical absorption spectrum have redshifts or blueshifts as a function of the laser parameter and the electric field. These parameters could be suitable tools for tuning the electronic and optical properties of the multibarrier structure.

Third-order optical nonlinearities in bulk and fs-laser inscribed waveguides in strengthened alkali aluminosilcate glass

Science.gov (United States)

Almeida, Gustavo F. B.; Almeida, Juliana M. P.; Martins, Renato J.; De Boni, Leonardo; Arnold, Craig B.; Mendonca, Cleber R.

2018-01-01

The development of advanced photonics devices requires materials with large optical nonlinearities, fast response times and high optical transparency, while at the same time allowing for the micro/nano-processing needed for integrated photonics. In this context, glasses have been receiving considerable attention given their relevant optical properties which can be specifically tailored by compositional control. Corning Gorilla® Glass (strengthened alkali aluminosilicate glass) is well-known for its use as a protective screen in mobile devices, and has attracted interest as a potential candidate for optical devices. Therefore, it is crucial not only to expand the knowledge on the fabrication of waveguides in Gorilla Glass under different regimes, but also to determine its nonlinear optical response, both using fs-laser pulses. Thus, this paper reports, for the first time, characterization of the third-order optical nonlinearities of Gorilla Glass, as well as linear and nonlinear characterization of waveguide written with femtosecond pulses under the low repetition rate regime (1 kHz).

Faraday rotation and magneto-optical figure of merit for the magnetite magnetic fluids

Directory of Open Access Journals (Sweden)

Kalandadze L.

2011-05-01

Full Text Available In the present paper, using magnetite magnetic fluids as examples, we consider the optical and magneto-optical properties of magnetic fluids based on particles of magnetic oxides, for the optical constants of the material of which, n and k , the relation k2 ≺≺ n2 holds. In this work the Faraday rotation is represented within the theoretical Maxwell-Garnett model. A theoretical analysis has shown that Faraday rotation for magnetic fluids is related to the Faraday rotation on the material of particles by the simple relation. According to this result  in specific experimental conditions the values of the Faraday rotation prorate to q , which is the occupancy of the volume of the magnetic fluid with magnetic particles and spectral dependences of effect in magnetic fluid and in the proper bulk magnetic are similar. We also show that the values of the magneto-optical figure of merit for ultrafine medium and for the bulk material are equal.

Effect of capping agents on optical and antibacterial properties of ...

Indian Academy of Sciences (India)

Administrator

unique optical properties resulting from quantum con- finement ... them suitable in application such as biomedical label- ling,4 solar ... All optical measurements were carried out at ..... QDs with biomolecules and to use them as biosensors,.

Optical properties of silver composite metamaterials

Energy Technology Data Exchange (ETDEWEB)

Orbons, S.M. [School of Physics, University of Melbourne, Victoria 3010 (Australia)]. E-mail: sorbons@ph.unimelb.edu.au; Freeman, D. [Centre for Ultrahigh-bandwidth Devices for Optical Systems, Laser Physics Centre, Australian National University, ACT 0200 (Australia); Luther-Davies, B. [Centre for Ultrahigh-bandwidth Devices for Optical Systems, Laser Physics Centre, Australian National University, ACT 0200 (Australia); Gibson, B.C. [Quantum Communications Victoria, School of Physics, University of Melbourne, Victoria 3010 (Australia); Huntington, S.T. [Quantum Communications Victoria, School of Physics, University of Melbourne, Victoria 3010 (Australia); Jamieson, D.N. [School of Physics, University of Melbourne, Victoria 3010 (Australia); Roberts, A. [School of Physics, University of Melbourne, Victoria 3010 (Australia)

2007-05-15

We present a computational and experimental study investigating the optical properties of nanoscale silver composite metamaterials fabricated by ion beam lithography. Both simulations and experimental results demonstrate high transmission efficiencies in the near infra-red through these devices. Implications for experimentally verifying the calculated near-field distributions of these materials are also discussed.

The applicability of physical optics in the millimetre and sub-millimetre spectral region. Part I: The ray tracing with diffraction on facets method

International Nuclear Information System (INIS)

Baran, A.J.; Hesse, Evelyn; Sourdeval, Odran

2017-01-01

Future satellite missions, from 2022 onwards, will obtain near-global measurements of cirrus at microwave and sub-millimetre frequencies. To realise the potential of these observations, fast and accurate light-scattering methods are required to calculate scattered millimetre and sub-millimetre intensities from complex ice crystals. Here, the applicability of the ray tracing with diffraction on facets method (RTDF) in predicting the bulk scalar optical properties and phase functions of randomly oriented hexagonal ice columns and hexagonal ice aggregates at millimetre frequencies is investigated. The applicability of RTDF is shown to be acceptable down to size parameters of about 18, between the frequencies of 243 and 874 GHz. It is demonstrated that RTDF is generally well within about 10% of T-matrix solutions obtained for the scalar optical properties assuming hexagonal ice columns. Moreover, on replacing electromagnetic scalar optical property solutions obtained for the hexagonal ice aggregate with the RTDF counterparts at size parameter values of about 18 or greater, the bulk scalar optical properties can be calculated to generally well within ±5% of an electromagnetic-based database. The RTDF-derived bulk scalar optical properties result in brightness temperature errors to generally within about ±4 K at 874 GHz. Differing microphysics assumptions can easily exceed such errors. Similar findings are found for the bulk scattering phase functions. This finding is owing to the scattering solutions being dominated by the processes of diffraction and reflection, both being well described by RTDF. The impact of centimetre-sized complex ice crystals on interpreting cirrus polarisation measurements at sub-millimetre frequencies is discussed. - Highlights: • A method of physical optics is shown to apply to size parameters as low as 18 in the mm and sub-mm-wave spectral regions. • Including ray tracing with diffraction on facets and diffraction at the cross-section of

Bulk-edge correspondence in topological transport and pumping

Science.gov (United States)

Imura, Ken-Ichiro; Yoshimura, Yukinori; Fukui, Takahiro; Hatsugai, Yasuhiro

2018-03-01

The bulk-edge correspondence (BEC) refers to a one-to-one relation between the bulk and edge properties ubiquitous in topologically nontrivial systems. Depending on the setup, BEC manifests in different forms and govern the spectral and transport properties of topological insulators and semimetals. Although the topological pump is theoretically old, BEC in the pump has been established just recently [1] motivated by the state-of-the-art experiments using cold atoms [2, 3]. The center of mass (CM) of a system with boundaries shows a sequence of quantized jumps in the adiabatic limit associated with the edge states. Despite that the bulk is adiabatic, the edge is inevitably non-adiabatic in the experimental setup or in any numerical simulations. Still the pumped charge is quantized and carried by the bulk. Its quantization is guaranteed by a compensation between the bulk and edges. We show that in the presence of disorder the pumped charge continues to be quantized despite the appearance of non-quantized jumps.

Investigation of the structural, electronic and optical properties of the cubic RbMF{sub 3} perovskites (M = Be, Mg, Ca, Sr and Ba) using modified Becke-Johnson exchange potential

Energy Technology Data Exchange (ETDEWEB)

Sandeep, E-mail: sndp.chettri@gmail.com [Department of Physics, Mizoram University, Aizawl, 796004 (India); Rai, D.P. [Department of Physics, Pachhunga University College, Mizoram University, 796001 (India); Shankar, A. [Department of Physics, University of North Bengal, Darjeeling, 734013 (India); Ghimire, M.P. [Condensed Matter Physics Research Center, Butwal-13, Rupandehi, Lumbini (Nepal); IFW-Dresden, Helmholtzstraße 20, D-01069, Dresden (Germany); Khenata, R. [Laboratoire de Physique Quantique de la Mati´ere et de Modélisation Mathématique LPQ3M, Université de Mascara, Mascara, 29000 (Algeria); Bin Omran, S. [Department of Physics and Astronomy, College of Science, King Saud University, P. O. Box 2455, Riyadh, 11451 (Saudi Arabia); Syrotyuk, S.V. [Semiconductor Electronics Department, Lviv Polytechnic National University, Lviv, 79013 (Ukraine); Thapa, R.K. [Department of Physics, Mizoram University, Aizawl, 796004 (India)

2017-05-01

The structural, electronic and optical properties of the cubic RbMF{sub 3} perovskites (M = Be, Mg, Ca, Sr, Ba) have been investigated using the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange and correlation potential was applied using the generalized gradient approximation for calculating the structural properties In addition, the modified Becke-Johnson (TB-mBJ) potential was used for calculating the electronic and optical properties. It was found that the lattice constant increases while the bulk modulus decreases with the change of cation (M) in going from Be to Ba in the RbMF{sub 3} perovskites (M = Be, Mg, Ca, Sr, Ba). The reflectivity and absorption properties were also studied using the mBJ method to understand the inter-band transitions and their possible applications in absorption devices in the UV-region. - Highlights: • Closer estimate of the band-gaps of RbMF{sub 3} with experimental results using GGA and mBJ results predicting them to be absorption devices and substrates for thin film growth. • The RbMF{sub 3} were also found to be potential candidate for in absorption devices in UV-region which were correlated to their calculated optical properties. • The materials are transparent, so may be used as substrates for thin film growth, for the optoelectric applications.

Interlayer excitons in a bulk van der Waals semiconductor.

Science.gov (United States)

Arora, Ashish; Drüppel, Matthias; Schmidt, Robert; Deilmann, Thorsten; Schneider, Robert; Molas, Maciej R; Marauhn, Philipp; Michaelis de Vasconcellos, Steffen; Potemski, Marek; Rohlfing, Michael; Bratschitsch, Rudolf

2017-09-21

Bound electron-hole pairs called excitons govern the electronic and optical response of many organic and inorganic semiconductors. Excitons with spatially displaced wave functions of electrons and holes (interlayer excitons) are important for Bose-Einstein condensation, superfluidity, dissipationless current flow, and the light-induced exciton spin Hall effect. Here we report on the discovery of interlayer excitons in a bulk van der Waals semiconductor. They form due to strong localization and spin-valley coupling of charge carriers. By combining high-field magneto-reflectance experiments and ab initio calculations for 2H-MoTe 2 , we explain their salient features: the positive sign of the g-factor and the large diamagnetic shift. Our investigations solve the long-standing puzzle of positive g-factors in transition metal dichalcogenides, and pave the way for studying collective phenomena in these materials at elevated temperatures.Excitons, quasi-particles of bound electron-hole pairs, are at the core of the optoelectronic properties of layered transition metal dichalcogenides. Here, the authors unveil the presence of interlayer excitons in bulk van der Waals semiconductors, arising from strong localization and spin-valley coupling of charge carriers.

Thermo-mechanical properties of W/Mo markers coatings deposited on bulk W

International Nuclear Information System (INIS)

Grigore, E; Ruset, C; Gherendi, M; Chioibasu, D; Hakola, A

2016-01-01

In the present paper marker structures consisting of W/Mo layers were deposited on bulk W samples by using a modified CMSII method. This technology, compared to standard CMSII, prevents the formation of nano-pore structures at interfaces. The thicknesses of the markers were in the range 20–35 μm to balance the requirements associated with the wall erosion in ITER and thermo-mechanical performances. The coatings structure and composition were evaluated by glow discharge optical emission spectrometry (GDOES), and energy dispersive x-ray spectroscopy measurements (EDX). The adhesion of the coatings to the substrate has been assessed by scratch test method. In order to evaluate their effectiveness as potential markers for fusion applications, the marker coatings have been tested in an electron beam facility at a temperature of 1000 °C and a power density of about 3 MW m −2 . A number of 300 pulses with duration of 420 s (35 testing hours) were applied on the marker coated samples. (paper)

Thermo-mechanical properties of W/Mo markers coatings deposited on bulk W

Science.gov (United States)

Grigore, E.; Ruset, C.; Gherendi, M.; Chioibasu, D.; Hakola, A.; contributors, JET

2016-02-01

In the present paper marker structures consisting of W/Mo layers were deposited on bulk W samples by using a modified CMSII method. This technology, compared to standard CMSII, prevents the formation of nano-pore structures at interfaces. The thicknesses of the markers were in the range 20-35 μm to balance the requirements associated with the wall erosion in ITER and thermo-mechanical performances. The coatings structure and composition were evaluated by glow discharge optical emission spectrometry (GDOES), and energy dispersive x-ray spectroscopy measurements (EDX). The adhesion of the coatings to the substrate has been assessed by scratch test method. In order to evaluate their effectiveness as potential markers for fusion applications, the marker coatings have been tested in an electron beam facility at a temperature of 1000 °C and a power density of about 3 MW m-2. A number of 300 pulses with duration of 420 s (35 testing hours) were applied on the marker coated samples.

Surface crystallization and magnetic properties of amorphous Fe80B20 alloy

International Nuclear Information System (INIS)

Vavassori, P.; Ronconi, F.; Puppin, E.

1997-01-01

We have studied the effects of surface crystallization on the magnetic properties of Fe 80 B 20 amorphous alloys. The surface magnetic properties have been studied with magneto-optic Kerr measurements, while those of bulk with a vibrating sample magnetometer. This study reveals that surface crystallization is similar to the bulk process but occurs at a lower temperature. At variance with previous results on other iron-based amorphous alloys the surface crystalline layer does not induce bulk magnetic hardening. Furthermore, both the remanence to saturation ratio and the bulk magnetic anisotropy do not show appreciable variations after the formation of the surface crystalline layer. The Curie temperature of the surface layer is lower with respect to the bulk of the sample. These effects can be explained by a lower boron concentration in the surface region of the as-cast amorphous alloy. Measurements of the chemical composition confirm a reduction of boron concentration in the surface region. copyright 1997 American Institute of Physics

Magneto-optic properties and optical parameter of thin MnCo films

Directory of Open Access Journals (Sweden)

E Attaran Kakhki

2009-09-01

Full Text Available Having precise hysterics loop of thin ferroelectric and ferromagnetic layers for optical switching and optical storages are important. A hysterieses loop can be achieved from a phenomenon call the magneto-optic effect. The magneto-optic effect is the rotation of a linear polarized electromagnetic wave propagated through a ferromagnetic medium. When light is transmitted through a layer of magnetic material the result is called the Faraday effects and in the reflection mode Kerr effect. In the present work we prepared a thin layer of MnxCo3-xO4 (0≤ x ≤ 1 and a binary form of MnO/Co3O4 by the spray pyrolysis method. The films have been characterized by a special set up of magneto-optic hysterics loop plotter containing a polarized He- Ne laser beam and a special electronic circuit. Faraday rotation were measured for these films by hysterics loop plotter and their optical properties were also obtained by spatial software designed for this purpose according to Swane Poel theoretical method. The measurements show that the samples at diluted Mn study has are ferromagnetic and the magneto-optic rotation show a good enhance respect to the single Co layers. Also, the study has shown that the MnCo oxide layer have two different energy gaps and by increasing of Mn this energy decreases and fall to 0.13 eV.

Screened coulomb hybrid DFT study on electronic structure and optical properties of anionic and cationic Te-doped anatase TiO2

KAUST Repository

Harb, Moussab

2013-01-01

The origin of the enhanced visible-light optical absorption in Te-doped bulk anatase TiO2 is investigated in the framework of DFT and DFPT within HSE06 in order to ensure accurate electronic structure and optical transition predictions. Various

Optical and electrical properties of electron-irradiated Cu(In,Ga)Se{sub 2} solar cells

Energy Technology Data Exchange (ETDEWEB)

Hirose, Y.; Warasawa, M. [Department of Electrical Engineering, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda 278-8510 (Japan); Takakura, K. [Department of Information, Communication and Electrical Engineering, Kumamoto National College of Technology, 2659-2 Suya, Koshi, Kumamoto 861-1102 (Japan); Kimura, S. [Department of Electrical Engineering, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda 278-8510 (Japan); Chichibu, S.F. [CANTech, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577 (Japan); Ohyama, H. [Department of Information, Communication and Electrical Engineering, Kumamoto National College of Technology, 2659-2 Suya, Koshi, Kumamoto 861-1102 (Japan); Sugiyama, M., E-mail: mutsumi@rs.noda.tus.ac.jp [Department of Electrical Engineering, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda 278-8510 (Japan)

2011-08-31

The optical and electrical properties of electron-irradiated Cu(In,Ga)Se{sub 2} (CIGS) solar cells and the thin films that composed the CIGS solar cell structure were investigated. The transmittance of indium tin oxide (ITO), ZnO:Al, ZnO:Ga, undoped ZnO, and CdS thin films did not change for a fluence of up to 1.5 x 10{sup 18} cm{sup -2}. However, the resistivity of ZnO:Al and ZnO:Ga, which are generally used as window layers for CIGS solar cells, increased with increasing irradiation fluence. For CIGS thin films, the photoluminescence peak intensity due to Cu-related point defects, which do not significantly affect solar cell performance, increased with increasing electron irradiation. In CIGS solar cells, decreasing J{sub SC} and increasing R{sub s} reflected the influence of irradiated ZnO:Al, and decreasing V{sub OC} and increasing R{sub sh} mainly tended to reflect the pn-interface properties. These results may indicate that the surface ZnO:Al thin film and several heterojunctions tend to degrade easily by electron irradiation as compared with the bulk of semiconductor-composed solar cells.

Optical properties of zinc titanate perovskite prepared by reactive RF sputtering

Science.gov (United States)

Müllerová, Jarmila; Šutta, Pavol; Medlín, Rostislav; Netrvalová, Marie; Novák, Petr

2017-12-01

In this paper we report results from optical transmittance spectroscopy complemented with data on structure from XRD measurements to determine optical properties of a series of ZnTiO3 perovskite thin films deposited on glass by reactive magnetron co-sputtering. The members of the series differ by the titanium content that was revealed as an origin of the changes not only in structure but also in dispersive optical properties. Low porosity has been discovered and calculated using the Bruggeman effective medium approximation. An apparent blue-shift of the optical band gap energies with increasing titanium content was observed. The observed band gap engineering is a good prospective for eg optoelectronic and photocatalytic applications of ZnTiO3.

The microstructure of MX-80 clay with respect to its bulk physical properties under different environmental conditions

International Nuclear Information System (INIS)

Pusch, R.

2001-03-01

A model of microstructural evolution of MX-80 buffer is presented in the report.Quantification of the microstructure is made by use of digitalized micrographs taken by transmission electron microscopy using suitably impregnated specimens with appropriate thickness. The model is termed MMM, a successor of the earlier GMM. Practically useful microstructural parameters refer to the fraction of a thin section that represents dense and soft parts of the clay matrix. The derived microstructural parameters are directly coupled to the most important bulk physical properties, i.e. the hydraulic conductivity, gas penetrability, swelling pressure and cation/anion diffusion capacities. The study has shown that even at very high densities, softer and more pervious zones exist in the form of interconnected 'external' voids filled with more or less dense clay gels. At bulk densities exceeding 2000 kg/m 3 after water saturation, the gel density is also high but for low bulk densities it may be so much reduced that the gels do not remain stable at high electrolyte content of the pore water. The fact that the density variations are small for high bulk densities means that the separation of matrix components ('fracturing') that is required for letting gas through is on the same order of magnitude as the bulk swelling pressure. For lower bulk densities, displacement or consolidation of the clay gels in 'external' voids is concluded to take place in conjunction with gas penetration. At high densities the limited degree of continuity and constrictions of the channels leading to anion-excluding charge conditions mean that the anion diffusion capacity is very low, while cation diffusion may be extensive because it takes place not only through channels but also through the inter lamellar space and along the surfaces of stacks of lamellae, i.e. by surface diffusion. Two Pre-Quaternary clays that have been investigated and characterized with respect to the microstructure represent two

The microstructure of MX-80 clay with respect to its bulk physical properties under different environmental conditions

Energy Technology Data Exchange (ETDEWEB)

Pusch, R. [Geodevelopment AB, Lund (Sweden)

2001-03-01

A model of microstructural evolution of MX-80 buffer is presented in the report.Quantification of the microstructure is made by use of digitalized micrographs taken by transmission electron microscopy using suitably impregnated specimens with appropriate thickness. The model is termed MMM, a successor of the earlier GMM. Practically useful microstructural parameters refer to the fraction of a thin section that represents dense and soft parts of the clay matrix. The derived microstructural parameters are directly coupled to the most important bulk physical properties, i.e. the hydraulic conductivity, gas penetrability, swelling pressure and cation/anion diffusion capacities. The study has shown that even at very high densities, softer and more pervious zones exist in the form of interconnected 'external' voids filled with more or less dense clay gels. At bulk densities exceeding 2000 kg/m{sup 3} after water saturation, the gel density is also high but for low bulk densities it may be so much reduced that the gels do not remain stable at high electrolyte content of the pore water. The fact that the density variations are small for high bulk densities means that the separation of matrix components ('fracturing') that is required for letting gas through is on the same order of magnitude as the bulk swelling pressure. For lower bulk densities, displacement or consolidation of the clay gels in 'external' voids is concluded to take place in conjunction with gas penetration. At high densities the limited degree of continuity and constrictions of the channels leading to anion-excluding charge conditions mean that the anion diffusion capacity is very low, while cation diffusion may be extensive because it takes place not only through channels but also through the inter lamellar space and along the surfaces of stacks of lamellae, i.e. by surface diffusion. Two Pre-Quaternary clays that have been investigated and characterized with respect to the

FINAL REPORT: Scalable Methods for Electronic Excitations and Optical Responses of Nanostructures: Mathematics to Algorithms to Observables

Energy Technology Data Exchange (ETDEWEB)

Chelikowsky, James R. [Univ. of Texas, Austin, TX (United States)

2013-04-01

Work in nanoscience has increased substantially in recent years owing to its potential technological applications and to fundamental scientific interest. A driving force for this activity is to capitalize on new phenomena that occurs at the nanoscale. For example, the physical confinement of electronic states, i.e., quantum confinement, can dramatically alter the electronic and optical properties of matter. A prime example of this occurs for the optical properties of nanoscale crystals such as those composed of elemental silicon. Silicon in the bulk state is optically inactive due to the small size of the optical gap, which can only be accessed by indirect transitions. However, at the nanoscale, this material becomes optically active. The size of the optical gap is increased by confinement and the conservation of crystal momentum ceases to hold, resulting in the viability of indirect transitions. Our work associated with this grant has focused on developing new scalable algorithms for describing the electronic and optical properties of matter at the nanoscale such as nano structures of silicon and related semiconductor properties.

Strain induced optical properties of BaReO3

Science.gov (United States)

Kumavat, Sandip R.; Kansara, Shivam; Gupta, Sanjeev K.; Sonvane, Yogesh

2018-05-01

Here, we have performed strain induce optical properties of BaReO3 by using density functional theory (DFT). We noticed that after applying intrinsic and extrinsic strain to the BaReO3, it shows the metallic behavior. We also studied optical properties, which show good activity in the ultraviolet region. The results show that after applying intrinsic and extrinsic strain to BaReO3 the absorption peaks are shifted towards the high UV region of the spectrum. Thus, we concluded that, BaReO3 material with extrinsic strain can be useful for high frequency UV device and optoelectronic devices.

Optical properties of cadmium sulfide nanocrystal film prepared by electrochemical synthesis at liquid-liquid interface

International Nuclear Information System (INIS)

Luan Yemei; An Maozhong; Lu Guoqi

2006-01-01

Dendritic nanocrystalline CdS film was deposited at liquid-liquid interface of surfactants and an electrolyte containing 4 mmol L -1 cadmium chloride (CdCl 2 ) and 16 mmol L -1 thioacetamide (CH 3 CSNH 2 ) with an initial pH value of 5 at 15 deg. C by electrochemical synthesis. The nanofilm was characterized by transmission electron microscopy (TEM), field emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM), ultraviolet visible (UV-vis) absorption spectroscopy and fluorescence spectroscopy. The surface morphology and particle size of the nanofilm were investigated by AFM, SEM and TEM, and the crystalline size was 30-50 nm. The thickness of the nanofilm calculated by optical absorption spectrum was 80 nm. The microstructure and composition of the nanofilm was investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), showing its polycrystalline structure consisting of CdS and Cd. Optical properties of the nanofilm were investigated systematically by UV-vis absorption and fluorescence spectroscopy. A λ onset blue shift compared with bulk CdS was observed in the absorption spectra. Fluorescence spectra of the nanofilm indicated that the CdS nanofilm emitted blue and green light. The nanocomposites film electrode will bring about anodic photocurrent during illumination, showing that the transfer of cavities produces photocurrent

Effects of sintering conditions on critical current properties and microstructures of MgB2 bulks

International Nuclear Information System (INIS)

Yamamoto, Akiyasu; Shimoyama, Jun-ichi; Ueda, Shinya; Katsura, Yukari; Iwayama, Isao; Horii, Shigeru; Kishio, Kohji

2005-01-01

The effects of heating conditions on critical current properties and microstructures of undoped MgB 2 bulks were systematically studied. Strong correlation was observed between J c and microstructures. The network structure with an excellent inter-grain connectivity of MgB 2 grains contributed to high-J c under low magnetic fields, and small grain size of MgB 2 enhanced the grain boundary flux pinning. Long time heating at low temperatures below the melting point of magnesium was discovered to be most effective for synthesis of MgB 2 bulks having strongly connected MgB 2 network structure with small grains. The sample heated at 550 deg. C for 1200 h recorded a high-J c of 4.02 x 10 5 A cm -2 at 20 K in self-field, while high-temperature and long time heating brought a significant grain growth which resulted in low J c

The influence of micropore size on the mechanical properties of bulk hydroxyapatite and hydroxyapatite scaffolds.

Science.gov (United States)

Cordell, Jacqueline M; Vogl, Michelle L; Wagoner Johnson, Amy J

2009-10-01

While recognized as a promising bone substitute material, hydroxyapatite (HA) has had limited use in clinical settings because of its inherent brittle behavior. It is well established that macropores ( approximately 100 microm) in a HA implant, or scaffold, are required for bone ingrowth, but recent research has shown that ingrowth is enhanced when scaffolds also contain microporosity. HA is sensitive to synthesis and processing parameters and therefore characterization for specific applications is necessary for transition to the clinic. To that end, the mechanical behavior of bulk microporous HA and HA scaffolds with multi-scale porosity (macropores between rods in the range of 250-350 microm and micropores within the rods with average size of either 5.96 microm or 16.2 microm) was investigated in order to determine how strength and reliability were affected by micropore size (5.96 microm versus 16.2 microm). For the bulk microporous HA, strength increased with decreasing micropore size in both bending (19 MPa to 22 MPa) and compression (71 MPa to 110 MPa). To determine strength reliability, the Weibull moduli for the bulk microporous HA were determined. The Weibull moduli for bending increased (became more reliable) with decreasing pore size (7 to 10) while the Weibull moduli for compression decreased (became less reliable) with decreasing pore size (9 to 6). Furthermore, the elastic properties of the bulk microporous HA (elastic modulus of 30 GPa) and the compressive strengths of the HA scaffolds with multi-scale porosity (8 MPa) did not vary with pore size. The mechanisms responsible for the trends observed were discussed.

Spectroscopic ellipsometry study of Cu2ZnSnS4 bulk poly-crystals

Science.gov (United States)

Levcenko, S.; Hajdeu-Chicarosh, E.; Garcia-Llamas, E.; Caballero, R.; Serna, R.; Bodnar, I. V.; Victorov, I. A.; Guc, M.; Merino, J. M.; Pérez-Rodriguez, A.; Arushanov, E.; León, M.

2018-04-01