Optical and structural behaviors of crosslinked polyvinyl alcohol thin films

NASA Astrophysics Data System (ADS)

Pandit, Subhankar; Kundu, Sarathi

2018-04-01

Polyvinyl Alcohol (PVA) has excellent properties like uniaxial tensile stress, chemical resistance, biocompatibility, etc. The properties of PVA further can be tuned by crosslinking process. In this work, a simple heat treatment method is used to find out the optimum crosslinking of PVA and the corresponding structural and optical responses are explored. The PVA crosslinking is done by exposing the films at different temperatures and time intervals. The optical property of pure and heat treated PVA films are investigated by UV-Vis absorption and photoluminescence emission spectroscopy and structural modifications are studied by Fourier Transform Infrared Spectroscopy (FTIR). The absorption peaks of pure PVA are observed at ≈ 280 and 335 nm and the corresponding emission is observed at ≈ 424 nm. The pure PVA showed modified optical behaviors after the heat treatment. In addition, dipping the PVA films in hot water (85°C) for nearly 20 minutes also show impact on both structural and optical properties. From FTIR spectroscopy, the changes in vibrational band positions confirm the structural modifications of PVA films.

Electronic structure and optical properties of CdSxSe1-x solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

NASA Astrophysics Data System (ADS)

Murphy, M. W.; Yiu, Y. M.; Ward, M. J.; Liu, L.; Hu, Y.; Zapien, J. A.; Liu, Yingkai; Sham, T. K.

2014-11-01

The electronic structure and optical properties of a series of iso-electronic and iso-structural CdSxSe1-x solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed.

The Optical Janus Effect: Asymmetric Structural Color Reflection Materials.

PubMed

England, Grant T; Russell, Calvin; Shirman, Elijah; Kay, Theresa; Vogel, Nicolas; Aizenberg, Joanna

2017-08-01

Structurally colored materials are often used for their resistance to photobleaching and their complex viewing-direction-dependent optical properties. Frequently, absorption has been added to these types of materials in order to improve the color saturation by mitigating the effects of nonspecific scattering that is present in most samples due to imperfect manufacturing procedures. The combination of absorbing elements and structural coloration often yields emergent optical properties. Here, a new hybrid architecture is introduced that leads to an interesting, highly directional optical effect. By localizing absorption in a thin layer within a transparent, structurally colored multilayer material, an optical Janus effect is created, wherein the observed reflected color is different on one side of the sample than on the other. A systematic characterization of the optical properties of these structures as a function of their geometry and composition is performed. The experimental studies are coupled with a theoretical analysis that enables a precise, rational design of various optical Janus structures with highly controlled color, pattern, and fabrication approaches. These asymmetrically colored materials will open applications in art, architecture, semitransparent solar cells, and security features in anticounterfeiting materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rationalizing the photophysical properties of BODIPY laser dyes via aromaticity and electron-donor-based structural perturbations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waddell, Paul G.; Liu, Xiaogang; Zhao, Teng

2015-05-01

The absorption and fluorescence properties of six boron dipyrromethene (BODIPY) laser dyes with simple non-aromatic substituents are rationalized by relating them to observable structural perturbations within the molecules of the dyes. An empirical relationship involving the structure and the optical properties is derived using a combination of single-crystal X-ray diffraction data, quantum chemical calculations and electronic constants: i.e. the tendency of the pyrrole bond lengths towards aromaticity and the UV-vis absorption and fluorescence wavelengths correlating with the electron-donor properties of the substituents. The effect of molecular conformation on the solid-state optical properties of the dyes is also discussed. The findingsmore » in this study also demonstrate the usefulness and limitations of using crystal structure data to develop structure-property relationships in this class of optical materials, contributing to the growing effort to design optoelectronic materials with tunable properties via molecular engineering.« less

First principle study of UHTC ternary diboride, Cr2AlB2

NASA Astrophysics Data System (ADS)

Rastogi, Anugya; Rajpoot, Priyanka; Verma, U. P.

2018-04-01

In this paper ab-initio study of the structural, electronic and optical properties of ternary metal boride Cr2AlB2 using full potential linear augmented plane wave (FP-LAPW) method based on the density functional theory (DFT). The study of structural properties shows that Cr2AlB2 is metallic in nature and have orthorhombic crystal structure. The optical properties show that it possess anisotropic behavior, which have wide applications in electricity production through concentration of solar power (CSP) technology. To the best of our knowledge, theoretical study of the optical properties of Cr2AlB2 is reported for the first time.

Electronic structure and optical properties of Si, Ge and diamond in the lonsdaleite phase.

PubMed

De, Amrit; Pryor, Craig E

2014-01-29

Crystalline semiconductors may exist in different polytypic phases with significantly different electronic and optical properties. In this paper, we calculate the electronic structure and optical properties of diamond, Si and Ge in the lonsdaleite (hexagonal diamond) phase using a transferable model empirical pseudopotential method with spin–orbit interactions. We calculate their band structures and extract various relevant parameters. Differences between the cubic and hexagonal phases are highlighted by comparing their densities of states. While diamond and Si remain indirect gap semiconductors in the lonsdaleite phase, Ge transforms into a direct gap semiconductor with a much smaller bandgap. We also calculate complex dielectric functions for different optical polarizations and find strong optical anisotropy. We further provide expansion parameters for the dielectric functions in terms of Lorentz oscillators.

Analysis of the structural, electronic and optic properties of Ni doped MgSiP{sub 2} semiconductor chalcopyrite compound

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kocak, Belgin, E-mail: koakbelgin@gmail.com; Ciftci, Yasemin Oztekin, E-mail: yasemin@gazi.edu.tr

2016-03-25

The structural, electronic band structure and optic properties of the Ni doped MgSiP{sub 2} chalcopyrite compound have been performed by using first-principles method in the density functional theory (DFT) as implemented in Vienna Ab-initio Simulation Package (VASP). The generalized gradient approximation (GGA) in the scheme of Perdew, Burke and Ernzerhof (PBE) is used for the exchange and correlation functional. The present lattice constant (a) follows generally the Vegard’s law. The electronic band structure, total and partial density of states (DOS and PDOS) are calculated. We present data for the frequency dependence of imaginary and real parts of dielectric functions ofmore » Ni doped MgSiP{sub 2}. For further investigation of the optical properties the reflectivity, refractive index, extinction coefficient and electron energy loss function are also predicted. Our obtained results indicate that the lattice constants, electronic band structure and optical properties of this compound are dependent on the substitution concentration of Ni.« less

Effects of doping of calcium atom(s) on structural, electronic and optical properties of binary strontium chalcogenides - A theoretical investigation using DFT based FP-LAPW methodology

NASA Astrophysics Data System (ADS)

Bhattacharjee, Rahul; Chattopadhyaya, Surya

2017-09-01

The effects of doping of Ca atom(s) on structural, electronic and optical properties of binary strontium chalcogenide semiconductor compounds have been investigated theoretically using DFT based FP-LAPW approach by modeling the rock-salt (B1) ternary alloys CaxSr1-xS, CaxSr1-xSe and CaxSr1-xTe at some specific concentrations 0 ≤ x ≤ 1 and studying their aforesaid properties. The exchange-correlation potentials for their structural properties have been computed using the Wu-Cohen generalized-gradient approximation (WC-GGA) scheme, while those for the electronic and optical properties have been computed using recently developed Tran-Blaha modified Becke-Johnson (TB-mBJ) scheme. In addition, we have computed the electronic and optical properties with the traditional BLYP and PBE-GGA schemes for comparison. The atomic and orbital origin of different electronic states in the band structure of each of the compounds have been identified from the respective density of states (DOS). Using the approach of Zunger and co-workers, the microscopic origin of band gap bowing has been discussed in term of volume deformation, charge exchange and structural relaxation. Bonding characteristics among the constituent atoms of each of the specimens have been discussed from their charge density contour plots. Optical properties of the binary compounds and ternary alloys have been investigated theoretically in terms of their respective dielectric function, refractive index, normal incidence reflectivity and optical conductivity. Several calculated results have been compared with available experimental and other theoretical data.

Structural, optical and field emission properties of urchin-shaped ZnO nanostructures.

PubMed

Al-Heniti, Saleh; Umar, Ahmad

2013-01-01

In this work, well-crystallized urchin-shaped ZnO structures were synthesized on silicon substrate by simple non-catalytic thermal evaporation process by using metallic zinc powder in the presence of oxygen as source materials for zinc and oxygen, respectively. The synthesized ZnO structures were characterized in detail in terms of their morphological, structural, optical and field emission properties. The detailed morphological investigations revealed that the synthesized structures possess urchin-shape and grown in high-density over the substrate surface. The detailed structural and optical characterizations revealed that the synthesized urchin-shaped ZnO structures are well-crystallized and exhibiting good optical properties. The field emission analysis for urchin-shaped ZnO structures exhibits a turn-on field of 4.6 V/microm. The emission current density reached to 0.056 mA/cm2 at an applied electrical field of 6.4 V/microm and shows no saturation. The calculated field enhancement factor 'beta', from the F-N plot, was found to be approximately 2.2 x 10(3).

Support for ACS COLL Division Symposium on: Patchy Particles and Surfaces of Engineered Heterogeneity: Synthesis to Dynamic Function

DTIC Science & Technology

2010-04-14

assembly of new materials with magnetic, optical , and photonic properties, self-replicating colloidal structures, and sensors. (a) Papers published in...Nanostructures: New Properties Driving New Synthetic Opportunities” This talk explored optical properties of assemblies of structured colloids. - I...including  experts on  optical  and photonic materials, numerical simulation, multiphase fluid flows, biomaterials,  bacteriology, tribology

Photonic structures based on hybrid nanocomposites

NASA Astrophysics Data System (ADS)

Husaini, Saima

In this thesis, photonic structures embedded with two types of nanomaterials, (i) quantum dots and (ii) metal nanoparticles are studied. Both of these exhibit optical and electronic properties different from their bulk counterpart due to their nanoscale physical structure. By integrating these nanomaterials into photonic structures, in which the electromagnetic field can be confined and controlled via modification of geometry and composition, we can enhance their linear and nonlinear optical properties to realize functional photonic structures. Before embedding quantum dots into photonic structures, we study the effect of various host matrices and fabrication techniques on the optical properties of the colloidal quantum dots. The two host matrices of interest are SU8 and PMMA. It is shown that the emission properties of the quantum dots are significantly altered in these host matrices (especially SU8) and this is attributed to a high rate of nonradiative quenching of the dots. Furthermore, the effects of fabrication techniques on the optical properties of quantum dots are also investigated. Finally a microdisk resonator embedded with quantum dots is fabricated using soft lithography and luminescence from the quantum dots in the disk is observed. We investigate the absorption and effective index properties of silver nanocomposite films. It is shown that by varying the fill factor of the metal nanoparticles and fabrication parameters such as heating time, we can manipulate the optical properties of the metal nanocomposite. Optimizing these parameters, a silver nanocomposite film with a 7% fill factor is prepared. A one-dimensional photonic crystal consisting of alternating layers of the silver nanocomposite and a polymer (Polymethyl methacrylate) is fabricated using spin coating and its linear and nonlinear optical properties are investigated. Using reflectivity measurements we demonstrate that the one-dimensional silver-nanocomposite-dielectric photonic crystal exhibits a 200% enhancement of the reflection band which is attributed to the interplay between the plasmon resonance of the silver nanoparticles and the Bloch modes of the photonic crystal. Nonlinear optical studies on this one-dimensional silver-nanocomposite-dielectric structure using z-scan measurements are conducted. These measurements indicate a three-fold enhancement in the nonlinear absorption coefficient when compared to a single film of comparable metal composite thickness.

Manipulation of local optical properties and structures in molybdenum-disulfide monolayers using electric field-assisted near-field techniques.

PubMed

Nozaki, Junji; Fukumura, Musashi; Aoki, Takaaki; Maniwa, Yutaka; Yomogida, Yohei; Yanagi, Kazuhiro

2017-04-05

Remarkable optical properties, such as quantum light emission and large optical nonlinearity, have been observed in peculiar local sites of transition metal dichalcogenide monolayers, and the ability to tune such properties is of great importance for their optoelectronic applications. For that purpose, it is crucial to elucidate and tune their local optical properties simultaneously. Here, we develop an electric field-assisted near-field technique. Using this technique we can clarify and tune the local optical properties simultaneously with a spatial resolution of approximately 100 nm due to the electric field from the cantilever. The photoluminescence at local sites in molybdenum-disulfide (MoS 2 ) monolayers is reversibly modulated, and the inhomogeneity of the charge neutral points and quantum yields is suggested. We successfully etch MoS 2 crystals and fabricate nanoribbons using near-field techniques in combination with an electric field. This study creates a way to tune the local optical properties and to freely design the structural shapes of atomic monolayers using near-field optics.

Highly optical transparency and thermally stable polyimides containing pyridine and phenyl pendant.

PubMed

Yao, Jianan; Wang, Chunbo; Tian, Chengshuo; Zhao, Xiaogang; Zhou, Hongwei; Wang, Daming; Chen, Chunhai

2017-01-01

In order to obtain highly optical transparency polyimides, two novel aromatic diamine monomers containing pyridine and kinky structures, 1,1-bis[4-(5-amino-2-pyridinoxy)phenyl]diphenylmethane (BAPDBP) and 1,1-bis[4-(5-amino-2-pyridinoxy)phenyl]-1-phenylethane (BAPDAP), were designed and synthesized. Polyimides based on BAPDBP, BAPDAP, 2,2-bis[4-(5-amino-2-pyridinoxy)phenyl]propane (BAPDP) with various commercial dianhydrides were prepared for comparison and structure-property relationships study. The structures of the polyimides were characterized by Fourier transform infrared (FT-IR) spectrometer, wide-angle X-ray diffractograms (XRD) and elemental analysis. Film properties including solubility, optical transparency, water uptake, thermal and mechanical properties were also evaluated. The introduction of pyridine and kinky structure into the backbones that polyimides presented good optical properties with 91-97% transparent at 500 nm and a low cut-off wavelength at 353-398 nm. Moreover, phenyl pendant groups of the polyimides showed high glass transition temperatures ( T g ) in the range of 257-281 °C. These results suggest that the incorporating pyridine, kinky and bulky substituents to polymer backbone can improve the optical transparency effectively without sacrificing the thermal properties.

Structural, elastic, electronic, optical and thermoelectric properties of the Zintl-phase Ae3AlAs3 (Ae = Sr, Ba)

NASA Astrophysics Data System (ADS)

Benahmed, A.; Bouhemadou, A.; Alqarni, B.; Guechi, N.; Al-Douri, Y.; Khenata, R.; Bin-Omran, S.

2018-05-01

First-principles calculations were performed to investigate the structural, elastic, electronic, optical and thermoelectric properties of the Zintl-phase Ae3AlAs3 (Ae = Sr, Ba) using two complementary approaches based on density functional theory. The pseudopotential plane-wave method was used to explore the structural and elastic properties whereas the full-potential linearised augmented plane wave approach was used to study the structural, electronic, optical and thermoelectric properties. The calculated structural parameters are in good consistency with the corresponding measured ones. The single-crystal and polycrystalline elastic constants and related properties were examined in details. The electronic properties, including energy band dispersions, density of states and charge-carrier effective masses, were computed using Tran-Blaha modified Becke-Johnson functional for the exchange-correlation potential. It is found that both studied compounds are direct band gap semiconductors. Frequency-dependence of the linear optical functions were predicted for a wide photon energy range up to 15 eV. Charge carrier concentration and temperature dependences of the basic parameters of the thermoelectric properties were explored using the semi-classical Boltzmann transport model. Our calculations unveil that the studied compounds are characterised by a high thermopower for both carriers, especially the p-type conduction is more favourable.

Control of Resonances and Optical Properties of Plasmonic-Patch Metamaterials

DTIC Science & Technology

2012-08-01

entitled "Control of resonances and optical properties of plasmonic-patch metamaterials", under Award No. FA2386-11-1-4707 The stated research goals...their photonic properties when nonlinear amplifying dye molecules are imbedded in the structures. We will particularly focus on three...metamaterial structures. 4. Measurement of plasmon resonance and florescence properties in the dye-doped metamaterials with and without the

Discriminating Canopy Structural Types from Optical Properties using AVIRIS Data in the Sierra National Forest in Central California

NASA Astrophysics Data System (ADS)

Huesca Martinez, M.; Garcia, M.; Roth, K. L.; Casas, A.; Ustin, S.

2015-12-01

There is a well-established need within the remote sensing community for improved estimation of canopy structure and understanding of its influence on the retrieval of leaf biochemical properties. The aim of this project was to evaluate the estimation of structural properties directly from hyperspectral data, with the broader goal that these might be used to constrain retrievals of canopy chemistry. We used NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) to discriminate different canopy structural types, defined in terms of biomass, canopy height and vegetation complexity, and compared them to estimates of these properties measured by LiDAR data. We tested a large number of optical metrics, including single narrow band reflectance and 1st derivative, sub-pixel cover fractions, narrow-band indices, spectral absorption features, and Principal Component Analysis components. Canopy structural types were identified and classified from different forest types by integrating structural traits measured by optical metrics using the Random Forest (RF) classifier. The classification accuracy was above 70% in most of the vegetation scenarios. The best overall accuracy was achieved for hardwood forest (>80% accuracy) and the lowest accuracy was found in mixed forest (~70% accuracy). Furthermore, similarly high accuracy was found when the RF classifier was applied to a spatially independent dataset, showing significant portability for the method used. Results show that all spectral regions played a role in canopy structure assessment, thus the whole spectrum is required. Furthermore, optical metrics derived from AVIRIS proved to be a powerful technique for structural attribute mapping. This research illustrates the potential for using optical properties to distinguish several canopy structural types in different forest types, and these may be used to constrain quantitative measurements of absorbing properties in future research.

The electronic structure, elastic and optical properties of Cu2ZnGe(SexS1 - x)4 alloys: density functional calculations

NASA Astrophysics Data System (ADS)

Shen, Kesheng; Jia, Guangrui; Zhang, Xianzhou; Jiao, Zhaoyong

2016-10-01

The electronic structure, elastic and optical properties of Cu2ZnGe(SexS1 - x)4 alloys are systematically analysed using first-principles calculations. The lattice parameters agree well with the theoretical and experimental values which are searched as complete as possible indicating our calculations are reliable. The elastic properties are investigated first and are compared with the similar compounds CZTS and CZTSe due to the unavailable experimental data currently. The variation of the optical properties caused by the increase of Se/S ratio is discussed. The static optical constants are calculated and the corrected values are also predicted according to the available experimental data.

To study the effect of doping concentration of silver on structural and optical properties of cadmium oxide (CdO) nanostructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Rajesh, E-mail: rkkaushik06@gmail.com; Dept. of Physics, Vaish College of Engineering, Rohtak-124001, Haryana; Sharma, Ashwani

The present work deals with study of structural and optical properties of Silver (Ag) doped Cadmium oxide (CdO) nanostructured synthesized by Chemical Co-precipitation Techniques followed by calcinations at small temperature. The doping concentrations were changing from 0.1 to 10 at% respectively. Structural analysis study of these calcined materials is carried out by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The optical properties of calcined samples were investigating by Fourier transformation infrared (FTIR)spectroscopy, UV-Visible Spectroscopy (UV-Vis). The structural properties analysis results revels that crystallite size are in the range of nano region and TEM results aremore » quite in accordance with XRD results.« less

Optical properties of a multibarrier structure under intense laser fields

NASA Astrophysics Data System (ADS)

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.

Lithium halide monolayers: Structural, electronic and optical properties by first principles study

NASA Astrophysics Data System (ADS)

Safari, Mandana; Maskaneh, Pegah; Moghadam, Atousa Dashti; Jalilian, Jaafar

2016-09-01

Using first principle study, we investigate the structural, electronic and optical properties of lithium halide monolayers (LiF, LiCl, LiBr). In contrast to graphene and other graphene-like structures that form hexagonal rings in plane, these compounds can form and stabilize in cubic shape interestingly. The type of band structure in these insulators is identified as indirect type and ionic nature of their bonds are illustrated as well. The optical properties demonstrate extremely transparent feature for them as a result of wide band gap in the visible range; also their electron transitions are indicated for achieving a better vision on the absorption mechanism in these kinds of monolayers.

Structural and Optical Properties of La1−xSrxTiO3+δ

PubMed Central

Gao, Lihong; Ma, Zhuang; Wang, Song; Wang, Fuchi; Yang, Cai

2014-01-01

La1−xSrxTiO3+δ has attracted much attention as an important perovskite oxide. However, there are rare reports on its optical properties, especially reflectivity. In this paper, its structural and optical properties were studied. The X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and spectrophotometer were used to characterize the sample. The results show that with increasing Sr concentration, the number of TiO6 octahedral layers in each “slab” increases and the crystal structure changes from layered to cubic structure. A proper Sr doping (x = 0.1) can increase the reflectivity, reaching 95% in the near infrared range, which is comparable with metal Al measured in the same condition. This indicates its potential applications as optical protective coatings or anti-radiation materials at high temperatures. PMID:28788115

Ultra-precise micro-motion stage for optical scanning test

NASA Astrophysics Data System (ADS)

Chen, Wen; Zhang, Jianhuan; Jiang, Nan

2009-05-01

This study aims at the application of optical sensing technology in a 2D flexible hinge test stage. Optical fiber sensor which is manufactured taking advantage of the various unique properties of optical fiber, such as good electric insulation properties, resistance of electromagnetic disturbance, sparkless property and availability in flammable and explosive environment, has lots of good properties, such as high accuracy and wide dynamic range, repeatable, etc. and is applied in 2D flexible hinge stage driven by PZT. Several micro-bending structures are designed utilizing the characteristics of the flexible hinge stage. And through experiments, the optimal micro-bending tooth structure and the scope of displacement sensor trip under this optimal micro-bending tooth structure are derived. These experiments demonstrate that the application of optical fiber displacement sensor in 2D flexible hinge stage driven by PZT substantially broadens the dynamic testing range and improves the sensitivity of this apparatus. Driving accuracy and positioning stability are enhanced as well. [1,2

Optical, Structural, and Thermal Properties of Cerium-Doped Zinc Borophosphate Glasses.

PubMed

Choi, Su-Yeon; Ryu, Bong-Ki

2015-11-01

In this study, we verify the relationship between the optical properties and structure of cerium-doped zinc borophosphate glasses that have concurrence of non-bridging oxygen (NBO) and bridging oxygen (BO), Ce3+ and Ce4+, and BO3 structure and BO4 structure. We prepared cerium-doped zinc borophosphate glass with various compositions, given by xCeO2-(100-x)[50ZnO-10B2O3 -40P2O5] (x = 1 mol% to 6 mol%), and analyzed their optical band energy, glass transition temperature, crystallization temperature, density, and molar volume. Some of the techniques used for analysis were Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). In the investigated glasses, the optical band gap energy decreased from 3.28 eV to 1.73 eV. From these results, we can deduce the changes when transitions occur from BO to NBO, from Ce3+ to Ce4+, and from the BO3 structure to the BO4 structure with increasing CeO2 content using FT-IR and XPS analysis. We also verified the changes in structural and physical properties from quantitative properties such as glass transition temperature, crystallization temperature, density, and molar volume.

Structural and optical properties of Na-doped ZnO films

NASA Astrophysics Data System (ADS)

Akcan, D.; Gungor, A.; Arda, L.

2018-06-01

Zn1-xNaxO (x = 0.0-0.05) solutions have been synthesized by the sol-gel technique using Zinc acetate dihydrate and Sodium acetate which were dissolved into solvent and chelating agent. Na-doped ZnO nanoparticles were obtained from solutions to find phase and crystal structure. Na-doped ZnO films have been deposited onto glass substrate by using sol-gel dip coating system. The effects of dopant concentration on the structure, morphology, and optical properties of Na-doped ZnO thin films deposited on glass substrate are investigated. Characterization of Zn1-xNaxO nanoparticles and thin films are examined using differential thermal analysis (DTA)/thermogravimetric analysis (TGA), Scanning electron microscope (SEM) and X-Ray diffractometer (XRD). Optical properties of Zn1-xNaxO thin films were obtained by using PG Instruments UV-Vis-NIR spectrophotometer in 190-1100 nm range. The structure, morphology, and optical properties of thin films are presented.

Investigation of the structural, optical and piezoelectric properties of ALD ZnO films on PEN substrates

NASA Astrophysics Data System (ADS)

Blagoev, B. S.; Aleksandrova, M.; Terziyska, P.; Tzvetkov, P.; Kovacheva, D.; Kolev, G.; Mehandzhiev, V.; Denishev, K.; Dimitrov, D.

2018-03-01

We present the results of studies on the structural, optical and piezoelectric properties of ZnO thin films deposited by ALD on flexible polyethylene naphthalate (PEN) substrates. Changes were observed in the optical transmission and crystal structures as the deposition temperature was varied. The electromechanical behavior, dielectric losses and voltage generated from ZnO flexible devices were investigated and discussed, in order to estimate their suitability for potential application as microgenerators activated by human motion.

Exaggeration and suppression of iridescence: the evolution of two-dimensional butterfly structural colours

PubMed Central

Wickham, Shelley; Large, Maryanne C.J; Poladian, Leon; Jermiin, Lars S

2005-01-01

Many butterfly species possess ‘structural’ colour, where colour is due to optical microstructures found in the wing scales. A number of such structures have been identified in butterfly scales, including three variations on a simple multi-layer structure. In this study, we optically characterize examples of all three types of multi-layer structure, as found in 10 species. The optical mechanism of the suppression and exaggeration of the angle-dependent optical properties (iridescence) of these structures is described. In addition, we consider the phylogeny of the butterflies, and are thus able to relate the optical properties of the structures to their evolutionary development. By applying two different types of analysis, the mechanism of adaptation is addressed. A simple parsimony analysis, in which all evolutionary changes are given an equal weighting, suggests convergent evolution of one structure. A Dollo parsimony analysis, in which the evolutionary ‘cost’ of losing a structure is less than that of gaining it, implies that ‘latent’ structures can be reused. PMID:16849221

Interplay of structural, optical and magnetic properties in Gd doped CeO{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soni, S.; Dalela, S., E-mail: sdphysics@rediffmail.com; Kumar, Sudish

In this research wok systematic investigation on the synthesis, characterization, optical and magnetic properties of Ce{sub 1-x}Gd{sub x}O{sub 2} (where x=0.02, 0.04, 0.06, and 0.10) synthesized using the Solid-state method. Structural, Optical and Magnetic properties of the samples were investigated by X-ray diffraction (XRD), UV-VIS-NIR spectroscopy and VSM. Fluorite structure is confirmed from the XRD measurement on Gd doped CeO{sub 2} samples. Magnetic studies showed that the Gd doped polycrystalline samples display room temperature ferromagnetism and the ferromagnetic ordering strengthens with the Gd concentration.

Ionic and Optical Properties of Methylammonium Lead Iodide Perovskite across the Tetragonal-Cubic Structural Phase Transition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoque, Md Nadim Ferdous; Islam, Nazifah; Li, Zhen

Practical hybrid perovskite solar cells (PSCs) must endure temperatures above the tetragonal-cubic structural phase transition of methylammonium lead iodide (MAPbI3). However, the ionic and optical properties of MAPbI3 in such a temperature range, and particularly, dramatic changes in these properties resulting from a structural phase transition, are not well studied. Herein, we report a striking contrast at approximately 45 degrees C in the ionic/electrical properties of MAPbl3 owing to a change of the ion activation energy from 0.7 to 0.5 eV, whereas the optical properties exhibit no particular transition except for the steady increase of the bandgap with temperature. Thesemore » observations can be explained by the 'continuous' nature of perovskite phase transition. We speculate that the critical temperature at which the ionic/electrical properties change, although related to crystal symmetry variation, is not necessarily the same temperature as when tetragonal-cubic structural phase transition occurs.« less

Elaboration and properties of hierarchically structured optical thin films of MIL-101(Cr).

PubMed

Demessence, Aude; Horcajada, Patricia; Serre, Christian; Boissière, Cédric; Grosso, David; Sanchez, Clément; Férey, Gérard

2009-12-14

Stable nanoparticles dispersions of the porous hybrid MIL-101(Cr) allow dip-coating of high quality optical thin films with dual hierarchical porous structure. Moreover, for the first time, mechanical and sorption properties of mesoporous MOFs based thin films are evaluated.

Correction: Conceptual design of tetraazaporphyrin- and subtetraazaporphyrin-based functional nanocarbon materials: electronic structures, topologies, optical properties, and methane storage capacities.

PubMed

Belosludov, Rodion V; Rhoda, Hannah M; Zhdanov, Ravil K; Belosludov, Vladimir R; Kawazoe, Yoshiyuki; Nemykin, Victor N

2017-08-02

Correction for 'Conceptual design of tetraazaporphyrin- and subtetraazaporphyrin-based functional nanocarbon materials: electronic structures, topologies, optical properties, and methane storage capacities' by Rodion V. Belosludov et al., Phys. Chem. Chem. Phys., 2016, 18, 13503-13518.

Comparative study on structural and optical properties of CdS films fabricated by three different low-cost techniques

NASA Astrophysics Data System (ADS)

Ravichandran, K.; Philominathan, P.

2009-03-01

Highly crystalline and transparent cadmium sulphide films were fabricated at relatively low temperature by employing an inexpensive, simplified spray technique using perfume atomizer (generally used for cosmetics). The structural, surface morphological and optical properties of the films were studied and compared with that prepared by conventional spray pyrolysis using air as carrier gas and chemical bath deposition. The films deposited by the simplified spray have preferred orientation along (1 0 1) plane. The lattice parameters were calculated as a = 4.138 Å and c = 6.718 Å which are well agreed with that obtained from the other two techniques and also with the standard data. The optical transmittance in the visible range and the optical band gap were found as 85% and 2.43 eV, respectively. The structural and optical properties of the films fabricated by the simplified spray are found to be desirable for opto-electronic applications.

Effect of Annealing Temperature on Structural, Optical, and Electrical Properties of Sol-Gel Spin-Coating-Derived Cu2ZnSnS4 Thin Films

NASA Astrophysics Data System (ADS)

Hosseinpour, Rabie; Izadifard, Morteza; Ghazi, Mohammad Ebrahim; Bahramian, Bahram

2018-02-01

The effect of annealing temperature on structural, optical, and electrical properties of Cu2ZnSnS4 (CZTS) thin films grown on a glass substrate by spin coating sol-gel technique has been studied. Structural study showed that all samples had kesterite crystalline structure. Scanning electron microscopy images showed that the crystalline quality of the samples was improved by heat treatment. Optical study showed that the energy gap values for the samples ranged from 1.55 eV to 1.78 eV. Moreover, good optical conductivity values (1012 S-1 to 1014 S-1) were obtained for the samples. Investigation of the electrical properties of the CZTS thin films showed that the carrier concentration increased significantly with the annealing temperature. The photoelectrical behavior of the samples revealed that the photocurrent under light illumination increased significantly. Overall, the results show that the CZTS thin films annealed at 500°C had better structural, optical, and electrical properties and that such CZTS thin films are desirable for use as absorber layers in solar cells. The photovoltaic properties of the CZTS layer annealed at 500°C were also investigated and the associated figure of merit calculated. The results showed that the fabricated ZnS-CZTS heterojunction exhibited good rectifying behavior but rather low fill factor.

Structure-based optics of centric diatom frustules: modulation of the in vivo light field for efficient diatom photosynthesis.

PubMed

Goessling, Johannes W; Su, Yanyan; Cartaxana, Paulo; Maibohm, Christian; Rickelt, Lars F; Trampe, Erik C L; Walby, Sandra L; Wangpraseurt, Daniel; Wu, Xia; Ellegaard, Marianne; Kühl, Michael

2018-07-01

The optical properties of diatom silicate frustules inspire photonics and nanotechnology research. Whether light interaction with the nano-structure of the frustule also affects diatom photosynthesis has remained unclear due to lack of information on frustule optical properties under more natural conditions. Here we demonstrate that the optical properties of the frustule valves in water affect light harvesting and photosynthesis in live cells of centric diatoms (Coscinodiscus granii). Microscale cellular mapping of photosynthesis around localized spot illumination demonstrated optical coupling of chloroplasts to the valve wall. Photonic structures of the three-layered C. granii valve facilitated light redistribution and efficient photosynthesis in cell regions distant from the directly illuminated area. The different porous structure of the two sides of the valve exhibited photon trapping and forward scattering of blue light enhancing photosynthetic active radiation inside the cell. Photonic structures of diatom frustules thus alter the cellular light field with implications on diatom photobiology. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Structure and optical properties of noble metal and oxide nanoparticles dispersed in various polysaccharide biopolymers

NASA Astrophysics Data System (ADS)

Djoković, V.; Božanic, D. K.; Vodnik, V. V.; Krsmanović, R. M.; Trandafilovic, L. V.; Dimitrijević-Branković, S.

2011-10-01

We present the results on the structure and the optical properties of noble metal (Ag, Au) and oxide (ZnO) nanoparticles synthesized by various methods in different polysaccharide matrices such as chitosan, glycogen, alginate and starch. The structure of the obtained nanoparticles was studied in detail with microscopic techniques (TEM, SEM), while the XPS spectroscopy was used to investigate the effects at the nanoparticle-biomolecule interfaces. The antimicrobial activity of the nanocomposite films with Ag nanoparticles was tested against the Staphylococcus aureus, Escherichia coli and Candida albicans pathogens. In addition, we will present the results on the structure and optical properties of the tryptophan amino acid functionalized silver nanoparticles dispersed in water soluble polymer matrices.

Modification of band gaps and optoelectronic properties of binary calcium chalcogenides by means of doping of magnesium atom(s) in rock-salt phase- a first principle based theoretical initiative

NASA Astrophysics Data System (ADS)

Debnath, Bimal; Sarkar, Utpal; Debbarma, Manish; Bhattacharjee, Rahul; Chattopadhyaya, Surya

2018-02-01

The band gaps and optoelectronic properties of binary calcium chalcogenide semiconductors have been modified theoretically by doping magnesium atom(s) into their respective rock-salt unit cells at some specific concentrations x = 0.0, 0.25, 0.50, 0.75 and 1.0 and confirmed such modifications by studying their structural, electronic and optical properties using DFT based FP-LAPW approach. The WC-GGA functional is used to calculate structural properties, while mBJ, B3LYP and WC-GGA are used for calculating electronic and optical properties. The concentration dependences of lattice parameter, bulk modulus and fundamental band gap for each alloy system exhibit nonlinearity. The atomic and orbital origin of different electronic states in the band structure of each compound are explored from its density of states (DOS). The microscopic origin of band gap bowing for each of the alloy systems is explored in terms of volume deformation, charge exchange and structural relaxation. The chemical bonds between the constituent atoms in each compound are found as ionic in nature. Optical properties of each specimen are calculated from its computed spectra of dielectric function, refractive index, extinction coefficient, normal incidence reflectivity, optical conductivity, optical absorption and energy loss function. Several calculated results have been compared with available experimental and other theoretical data.

Luminescence and related properties of nanocrystalline porous silicon

NASA Astrophysics Data System (ADS)

Koshida, N.

This document is part of subvolume C3 'Optical Properties' of volume 34 'Semiconductor quantum structures' of Landolt-Börnstein, Group III, Condensed Matter, on the optical properties of quantum structures based on group IV semiconductors. It discusses luminescence and related properties of nanocrystalline porous silicon. Topics include an overview of nanostructured silicon, its fabrication technology, and properties of nanocrystalline porous silicon such as confinement effects, photoluminescence, electroluminesce, carrier charging effects, ballistic transport and emission, and thermally induced acoustic emission.

Optical properties of zinc titanate perovskite prepared by reactive RF sputtering

NASA Astrophysics Data System (ADS)

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.

Spectral ellipsometry studying of iron's optical and electronic properties

NASA Astrophysics Data System (ADS)

Chernukha, Yevheniia; Stashchuk, Vasyl S.; Polianska, Olena; Oshtuk, Olexsandr

2014-05-01

Fe's optical and electronic properties were investigated at room temperature in different structural states. The sample's surface was explored in wide spectral range λ = 0,23-17,0 μm (E = 4,96 - 0,07 еV ) by the Beatty's spectral ellipsometry method. While an experiment was carried out ellipsometry parameters Δ and ψ were measure near the principal angle of incidence. The refraction index R , permittivity Ɛ and optical conductivity σ( hν ) , that is proportional to the interband density of electronic states, were calculated using these parameters. Fe's optical conductivities in liquid, amorphous and crystalline states were compared in this work. The optical conductivity was calculated using the published data of the iron's density of electronic states in crystalline, amorphous and liquid states for the comparison of the experimental and theoretical results. It is shown that, at structural transformations "amorphous, liquid state- crystalline state", the optical properties of metallic iron are determined, in the first turn, by the nearest neighborhood, and the electronic structure is not subjected to significant modifications.

Electronic structure and optical properties of triangular GaAs/AlGaAs quantum dots: Exciton and impurity states

NASA Astrophysics Data System (ADS)

Tiutiunnyk, A.; Akimov, V.; Tulupenko, V.; Mora-Ramos, M. E.; Kasapoglu, E.; Ungan, F.; Sökmen, I.; Morales, A. L.; Duque, C. A.

2016-03-01

Electronic structure and optical properties in equilateral triangular GaAs/Al0.3Ga0.7As quantum dots are studied extensively. The effects of donor and acceptor impurity atoms positioned in the orthocenter of the triangle, as well as of the external DC electric field are taken into account. Binding energies of the impurity, exciton energies, interband photoluminescence peak positions as well as linear and non-linear optical properties in THz range caused by transitions between excitonic states are calculated and discussed.

Optical and structural properties of Nd:MgO:LiNbO3 crystal irradiated by 2.8-MeV He ions

NASA Astrophysics Data System (ADS)

Jia, Chuan-Lei; Li, Song; Song, Xiao-Xiao

2017-07-01

We report the optical and structural properties of helium-implanted optical waveguides in Nd:MgO:LiNbO3 laser crystals. The prism-coupling method is used to investigate the dark-mode properties at the wavelength of 632.8 nm. The spontaneous generation of ultraviolet, blue, red, and near-infrared fluorescence emissions is demonstrated under excitation with an 808-nm laser diode. The effects of ion irradiation on the structural properties are characterized using the high-resolution X-ray diffraction technique. The results show that the initial luminescence properties of Nd:MgO:LiNbO3 crystals are slightly modified by irradiation with 2.8 MeV He ions at fluences of 1.5 × 1016 ions/cm2 at room temperature.

Design of intelligent mesoscale periodic array structures utilizing smart hydrogel

NASA Technical Reports Server (NTRS)

Sunkara, H. B.; Penn, B. G.; Frazier, D. O.; Weissman, J. M.; Asher, S. A.

1996-01-01

Mesoscale Periodic Array Structures (MPAS, also known as crystalline colloidal arrays), composed of aqueous or nonaqueous dispersions of self-assembled submicron colloidal spheres are emerging toward the development of advanced optical devices for technological applications. This is because of their unique optical diffraction properties and the ease with which these intriguing properties can be modulated experimentally. Moreover our recent advancements in this area which include 'locking' the liquid MPAS into solid or semisolid polymer matrices for greater stability with longer life span, and incorporation of CdS quantum dots and laser dyes into colloidal spheres to obtain nonlinear optical (NLO) responses further corroborate the use of MPAS in optical technology. Our long term goal is fabrication of all-optical and electro-optical devices such as spatial light modulators for optical signal processing and flat panel display devices by utilizing intelligent nonlinear periodic array structural materials. Here we show further progress in the design of novel linear MPAS which have the ability to sense and respond to an external source such as temperature. This is achieved by combining the self-assembly properties of polymer colloidal spheres and thermoshrinking properties of smart polymer gels. At selected temperatures the periodic array efficiently Bragg diffracts light and transmits most of the light at other temperatures. Hence these intelligent systems are of potential use as fixed notch filters optical switches or limiters to protect delicate optical sensors from high intensity laser radiation.

Structured Light-Matter Interactions Enabled By Novel Photonic Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Litchinitser, Natalia; Feng, Liang

The synergy of complex materials and complex light is expected to add a new dimension to the science of light and its applications [1]. The goal of this program is to investigate novel phenomena emerging at the interface of these two branches of modern optics. While metamaterials research was largely focused on relatively “simple” linearly or circularly polarized light propagation in “complex” nanostructured, carefully designed materials with properties not found in nature, many singular optics studies addressed “complex” structured light transmission in “simple” homogeneous, isotropic, nondispersive transparent media, where both spin and orbital angular momentum are independently conserved. However, ifmore » both light and medium are complex so that structured light interacts with a metamaterial whose optical materials properties can be designed at will, the spin or angular momentum can change, which leads to spin-orbit interaction and many novel optical phenomena that will be studied in the proposed project. Indeed, metamaterials enable unprecedented control over light propagation, opening new avenues for using spin and quantum optical phenomena, and design flexibility facilitating new linear and nonlinear optical properties and functionalities, including negative index of refraction, magnetism at optical frequencies, giant optical activity, subwavelength imaging, cloaking, dispersion engineering, and unique phase-matching conditions for nonlinear optical interactions. In this research program we focused on structured light-matter interactions in complex media with three particularly remarkable properties that were enabled only with the emergence of metamaterials: extreme anisotropy, extreme material parameters, and magneto-electric coupling–bi-anisotropy and chirality.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pagare, Gitanjali, E-mail: gita-pagare@yahoo.co.in; Jain, Ekta, E-mail: jainekta05@gmail.com; Sanyal, S. P., E-mail: sps.physicsbu@gmail.com

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.more » 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.« less

Core–shell interaction and its impact on the optical absorption of pure and doped core-shell CdSe/ZnSe nanoclusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xinqin; Cui, Yingqi; Zeng, Qun

The structural, electronic, and optical properties of core-shell nanoclusters, (CdSe){sub x}@(CdSe){sub y} and their Zn-substituted complexes of x = 2–4 and y = 16–28, were studied with density functional theory calculations. The substitution was applied in the cores, the shells, and/or the whole clusters. All these clusters are characterized by their core-shell structures in which the core-shell interaction was found different from those in core or in shell, as reflected by their bondlengths, volumes, and binding energies. Moreover, the core and shell combine together to compose a new cluster with electronic and optical properties different from those of separated individuals,more » as reflected by their HOMO-LUMO gaps and optical absorptions. With the substitution of Cd by Zn, the structural, electronic, and optical properties of clusters change regularly. The binding energy increases with Zn content, attributed to the strong Zn–Se bonding. For the same core/shell, the structure with a CdSe shell/core has a narrower gap than that with a ZnSe shell/core. The optical absorption spectra also change accordingly with Zn substitution. The peaks blueshift with increasing Zn concentration, accompanying with shape variations in case large number of Cd atoms are substituted. Our calculations reveal the core-shell interaction and its influence on the electronic and optical properties of the core-shell clusters, suggesting a composition–structure–property relationship for the design of core-shell CdSe and ZnSe nanoclusters.« less

Study of Electronic Structure, Thermal Conductivity, Elastic and Optical Properties of α, β, γ-Graphyne

PubMed Central

Hou, Xun; Xie, Zhongjing; Li, Chunmei; Li, Guannan; Chen, Zhiqian

2018-01-01

In recent years, graphyne was found to be the only 2D carbon material that has both sp and sp2 hybridization. It has received significant attention because of its great potential in the field of optoelectronics, which arises due to its small band gap. In this study, the structural stability, electronic structure, elasticity, thermal conductivity and optical properties of α, β, γ-graphynes were investigated using density functional theory (DFT) systematically. γ-graphyne has the largest negative cohesive energy and thus the most stable structure, while the β-graphyne comes 2nd. Both β and γ-graphynes have sp-sp, sp-sp2 and sp2-sp2 hybridization bonds, of which γ-graphyne has shorter bond lengths and thus larger Young’s modulus. Due to the difference in acetylenic bond in the structure cell, the effect of strain on the electronic structure varies between graphynes: α-graphyne has no band gap and is insensitive to strain; β-graphyne’s band gap has a sharp up-turn at 10% strain, while γ-graphyne’s band gap goes up linearly with the strain. All the three graphynes exhibit large free carrier concentration and these free carriers have small effective mass, and both free carrier absorption and intrinsic absorption are found in the light absorption. Based on the effect of strain, optical properties of three structures are also analyzed. It is found that the strain has significant impacts on their optical properties. In summary, band gap, thermal conductivity, elasticity and optical properties of graphyne could all be tailored with adjustment on the amount of acetylenic bonds in the structure cell. PMID:29370070

Study of Electronic Structure, Thermal Conductivity, Elastic and Optical Properties of α, β, γ-Graphyne.

PubMed

Hou, Xun; Xie, Zhongjing; Li, Chunmei; Li, Guannan; Chen, Zhiqian

2018-01-25

In recent years, graphyne was found to be the only 2D carbon material that has both sp and sp² hybridization. It has received significant attention because of its great potential in the field of optoelectronics, which arises due to its small band gap. In this study, the structural stability, electronic structure, elasticity, thermal conductivity and optical properties of α, β, γ-graphynes were investigated using density functional theory (DFT) systematically. γ-graphyne has the largest negative cohesive energy and thus the most stable structure, while the β-graphyne comes 2nd. Both β and γ-graphynes have sp-sp, sp-sp² and sp²-sp² hybridization bonds, of which γ-graphyne has shorter bond lengths and thus larger Young's modulus. Due to the difference in acetylenic bond in the structure cell, the effect of strain on the electronic structure varies between graphynes: α-graphyne has no band gap and is insensitive to strain; β-graphyne's band gap has a sharp up-turn at 10% strain, while γ-graphyne's band gap goes up linearly with the strain. All the three graphynes exhibit large free carrier concentration and these free carriers have small effective mass, and both free carrier absorption and intrinsic absorption are found in the light absorption. Based on the effect of strain, optical properties of three structures are also analyzed. It is found that the strain has significant impacts on their optical properties. In summary, band gap, thermal conductivity, elasticity and optical properties of graphyne could all be tailored with adjustment on the amount of acetylenic bonds in the structure cell.

Effect of the KOH chemical treatment on the optical and photocatalytic properties of BiVO4 thin films

NASA Astrophysics Data System (ADS)

Mirabal-Rojas, R.; Depablos-Rivera, O.; Thalluri, S. M.; Medina, J. C.; Bizarro, M.; Perez-Alvarez, J.; Rodil, S. E.; Zeinert, A.

2016-04-01

In this work, we present the structural, optical and photocatalytic properties of BiVO4 thin films produced by a dual-magnetron sputtering process using both Bi2O3 (α-phase, 99.98 % purity) and V (99.9 % purity) targets under Ar/O2 atmosphere with a ratio of 18:2. The films were deposited varying the power applied to the targets to obtain stoichiometric films, and the monoclinic structure was achieved by post-deposition annealing. The dual process was chosen to better control the Bi/V ratio since Bi and V have very different sputtering yields. In particular, the influence of a chemical treatment using potassium hydroxide (KOH) on the optical properties and different dye discolorations (acid blue 113 and methyl orange) is discussed. The optical properties were studied by reflectance and transmittance spectroscopy, where the spectra were fitted to obtain the refractive index dispersion and the optical band gap of the BiVO4 as a function of the film structure, as determined by X-ray diffraction and Raman spectroscopy.

LED lamp or bulb with remote phosphor and diffuser configuration with enhanced scattering properties

DOEpatents

Tong, Tao; Le Toquin, Ronan; Keller, Bernd; Tarsa, Eric; Youmans, Mark; Lowes, Theodore; Medendorp, Jr., Nicholas W; Van De Ven, Antony; Negley, Gerald

2014-11-11

An LED lamp or bulb is disclosed that comprises a light source, a heat sink structure and an optical cavity. The optical cavity comprises a phosphor carrier having a conversions material and arranged over an opening to the cavity. The phosphor carrier comprises a thermally conductive transparent material and is thermally coupled to the heat sink structure. An LED based light source is mounted in the optical cavity remote to the phosphor carrier with light from the light source passing through the phosphor carrier. A diffuser dome is included that is mounted over the optical cavity, with light from the optical cavity passing through the diffuser dome. The properties of the diffuser, such as geometry, scattering properties of the scattering layer, surface roughness or smoothness, and spatial distribution of the scattering layer properties may be used to control various lamp properties such as color uniformity and light intensity distribution as a function of viewing angle.

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

NASA Astrophysics Data System (ADS)

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.

Thermophysical and Optical Properties of Semiconducting Ga2Te3 Melt

NASA Technical Reports Server (NTRS)

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.

The Tuning of Optical Properties of Nanoscale MOFs-Based Thin Film through Post-Modification.

PubMed

Yin, Wenchang; Tao, Cheng-An; Zou, Xiaorong; Wang, Fang; Qu, Tianlian; Wang, Jianfang

2017-08-29

Optical properties, which determine the application of optical devices in different fields, are the most significant properties of optical thin films. In recent years, Metal-organic framework (MOF)-based optical thin films have attracted increasing attention because of their novel optical properties and important potential applications in optical and photoelectric devices, especially optical thin films with tunable optical properties. This study reports the first example of tuning the optical properties of a MOF-based optical thin film via post-modification. The MOF-based optical thin film was composed of NH₂-MIL-53(Al) nanorods (NRs) (MIL: Materials from Institute Lavoisier), and was constructed via a spin-coating method. Three aldehydes with different lengths of carbon chains were chosen to modify the MOF optical thin film to tune their optical properties. After post-modification, the structural color of the NH₂-MIL-53(Al) thin film showed an obvious change from purple to bluish violet and cyan. The reflection spectrum and the reflectivity also altered in different degrees. The effective refractive index ( n eff ) of MOFs thin film can also be tuned from 1.292 to 1.424 at a wavelength of 750 nm. The success of tuning of the optical properties of MOFs thin films through post-modification will make MOFs optical thin films meet different needs of optical properties in various optical and optoelectronic devices.

The Tuning of Optical Properties of Nanoscale MOFs-Based Thin Film through Post-Modification

PubMed Central

Zou, Xiaorong; Wang, Fang; Qu, Tianlian; Wang, Jianfang

2017-01-01

Optical properties, which determine the application of optical devices in different fields, are the most significant properties of optical thin films. In recent years, Metal-organic framework (MOF)-based optical thin films have attracted increasing attention because of their novel optical properties and important potential applications in optical and photoelectric devices, especially optical thin films with tunable optical properties. This study reports the first example of tuning the optical properties of a MOF-based optical thin film via post-modification. The MOF-based optical thin film was composed of NH2-MIL-53(Al) nanorods (NRs) (MIL: Materials from Institute Lavoisier), and was constructed via a spin-coating method. Three aldehydes with different lengths of carbon chains were chosen to modify the MOF optical thin film to tune their optical properties. After post-modification, the structural color of the NH2-MIL-53(Al) thin film showed an obvious change from purple to bluish violet and cyan. The reflection spectrum and the reflectivity also altered in different degrees. The effective refractive index (neff) of MOFs thin film can also be tuned from 1.292 to 1.424 at a wavelength of 750 nm. The success of tuning of the optical properties of MOFs thin films through post-modification will make MOFs optical thin films meet different needs of optical properties in various optical and optoelectronic devices. PMID:28850057

Optical and structural properties of Bi-based nanoparticles prepared via pulsed Nd:YAG laser ablation in organic liquids

NASA Astrophysics Data System (ADS)

Dadashi, S.; Poursalehi, R.; Delavari, H.

2018-06-01

Colloidal Bi/Bi2O3 and single phase Bi nanoparticles were synthesized by pulsed Nd:YAG laser ablation of metallic bismuth target in different organic liquids. In this research, the structural characteristic, optical properties, and colloidal stability of Bi and Bi/Bi2O3 nanoparticles have been studied. Furthermore, the mechanism of nanoparticles formation in liquid media by laser ablation of Bi-based nanoparticles was proposed in different liquid environments based on their chemical nature. X-ray diffraction, scanning electron microscopy and optical extinction spectroscopy indicate the formation of pure Bi and Bi/Bi2O3 nanoparticles with mean size of 32, 43 and 54 nm in methanol, ethanol, and EMK, respectively, which indicate a mixture of different phases including rhombohedra crystal structure of Bi, monoclinic α-Bi2O3, and tetragonal β-Bi2O3. Finally, this research demonstrates the effect of the surrounding environment on characteristic properties of nanoparticles and clarifies the size, structural characteristics, and optical properties of the synthesized nanoparticles.

Size effects on the structural, electronic, and optical properties of (5,0) finite-length carbon nanotube: An ab-initio electronic structure study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tarighi Ahmadpour, Mahdi; Rostamnejadi, Ali; Hashemifar, S. Javad

2016-07-07

We use density functional computations to study the zero temperature structural, electronic, magnetic, and optical properties of (5,0) finite carbon nanotubes (FCNT), with length in the range of 4–44 Å. It is found that the structural and electronic properties of (5,0) FCNTs, in the ground state, converge at a length of about 30 Å, while the excited state properties exhibit long-range edge effects. We discuss that curvature effects enhance energy gap of FCNTs, in contrast to the known trend in the periodic limit. It is seen that compensation of curvature effects in two special small sizes may give rise to spontaneous magnetization.more » The obtained cohesive energies provide some insights into the effects of environment on the growth of FCNTs. The second-order difference of the total energies reveals an important magic size of about 15 Å. The optical and dynamical magnetic responses of the FCNTs to polarized electromagnetic pulses are studied by time dependent density functional theory. The results show that the static and dynamic magnetic properties mainly come from the edge carbon atoms. The optical absorption properties are described in terms of local field effects and characterized by Casida linear response method.« less

First-principles calculations of the structural, electronic, optical and thermal properties of the BNxAs1-x alloys

NASA Astrophysics Data System (ADS)

Hamioud, L.; Boumaza, A.; Touam, S.; Meradji, H.; Ghemid, S.; El Haj Hassan, F.; Khenata, R.; Omran, S. Bin

2016-06-01

The present paper aims to study the structural, electronic, optical and thermal properties of the boron nitride (BN) and BAs bulk materials as well as the BNxAs1-x ternary alloys by employing the full-potential-linearised augmented plane wave method within the density functional theory. The structural properties are determined using the Wu-Cohen generalised gradient approximation that is based on the optimisation of the total energy. For band structure calculations, both the Wu-Cohen generalised gradient approximation and the modified Becke-Johnson of the exchange-correlation energy and potential, respectively, are used. We investigated the effect of composition on the lattice constants, bulk modulus and band gap. Deviations of the lattice constants and the bulk modulus from the Vegard's law and the linear concentration dependence, respectively, were observed for the alloys where this result allows us to explain some specific behaviours in the electronic properties of the alloys. For the optical properties, the calculated refractive indices and the optical dielectric constants were found to vary nonlinearly with the N composition. Finally, the thermal effect on some of the macroscopic properties was predicted using the quasi-harmonic Debye model in which the lattice vibrations are taken into account.

The formation and optical properties of planar waveguide in laser crystal Nd:YGG by carbon ion implantation

NASA Astrophysics Data System (ADS)

Zhao, Jin-Hua; Qin, Xi-Feng; Wang, Feng-Xiang; Jiao, Yang; Guan, Jing; Fu, Gang

2017-10-01

As one kind of prominent laser crystal, Nd:Y3Ga5O12 (Nd:YGG) crystal has outstanding performance on laser excitation at multi-wavelength which have shown promising applications in optical communication field. In addition, Nd:YGG crystal has potential applications in medical field due to its ability of emit the laser at 1110 nm. Optical waveguide structure with high quality could improve the efficiency of laser emission. In this work, we fabricated the optical planar waveguide on Nd:YGG crystal by medium mass ion implantation which was convinced an effective method to realize a waveguide structure with superior optical properties. The sample is implanted by C ions at energy of 5.0 MeV with the fluence of 1 × 1015 ions/cm2. We researched the optical propagation properties in the Nd:YGG waveguide by end-face coupling and prism coupling method. The Nd ions fluorescent properties are obtained by a confocal micro-luminescence measurement. The fluorescent properties of Nd ions obtained good reservation after C ion implantation. Our work has reference value for the application of Nd:YGG crystal in the field of optical communication.

Microstructural, optical and electrical transport properties of Cd-doped SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Ahmad, Naseem; Khan, Shakeel; Mohsin Nizam Ansari, Mohd

2018-03-01

We have successfully investigated the structural, optical and dielectric properties of Cd assimilated SnO2 nanoparticles synthesized via very convenient precipitation route. The structural properties were studied by x-ray diffraction method (XRD) and Fourier Transform Infrared (FTIR) Spectroscopy. As-synthesized samples in the form of powder were examined for its morphology and average particle size by Transmission electron microscopy (TEM). The optical properties were studied by diffuse reflectance spectroscopy. Dielectric properties such that complex dielectric constant and ac conductivity were investigated by LCR meter. Average crystallite size calculated by XRD and average particle size obtained from TEM were found to be consistent and below 50 nm for all samples. The optical band gap of as-synthesized powder samples from absorption study was found in the range of 3.76 to 3.97 eV. The grain boundary parameters such that Rgb, Cgb and τ were evaluated using impedance spectroscopy.

The structural, electronic and optical properties of Nd doped ZnO using first-principles calculations

NASA Astrophysics Data System (ADS)

Wen, Jun-Qing; Zhang, Jian-Min; Chen, Guo-Xiang; Wu, Hua; Yang, Xu

2018-04-01

The density functional theory calculations using general gradient approximation (GGA) applying Perdew-Burke-Ernzerhof (PBE) as correlation functional have been systematically performed to research the formation energy, the electronic structures, band structures, total and partial DOS, and optical properties of Nd doping ZnO with the content from 6.25% to 12.5%. The formation energies are negative for both models, which show that two structures are energetically stable. Nd doping ZnO crystal is found to be a direct band gap semiconductor and Fermi level shifts upward into conduction band, which show the properties of n-type semiconductor. Band structures are more compact after Nd doping ZnO, implying that Nd doping induces the strong interaction between different atoms. Nd doping ZnO crystal presents occupied states at near Fermi level, which mainly comes from the Nd 4f orbital. The calculated optical properties imply that Nd doping causes a red-shift of absorption peaks, and enhances the absorption of the visible light.

A novel structure of gel grown strontium cyanurate crystal and its structural, optical, electrical characterization

NASA Astrophysics Data System (ADS)

Divya, R.; Nair, Lekshmi P.; Bijini, B. R.; Nair, C. M. K.; Gopakumar, N.; Babu, K. Rajendra

2017-12-01

Strontium cyanurate crystals with novel structure and unique optical property like mechanoluminescence have been grown by conventional gel method. Transparent crystals were obtained. The single crystal X-ray diffraction analysis reveals the exquisite structure of the grown crystal. The crystal is centrosymmetric and has a three dimensional polymeric structure. The powder X ray diffraction analysis confirms its crystalline nature. The functional groups present in the crystal were identified by Fourier transform infrared spectroscopy. Elemental analysis confirmed the composition of the complex. A study of thermal properties was done by thermo gravimetric analysis and differential thermal analysis. The optical properties like band gap, refractive index and extinction coefficient were evaluated from the UV visible spectral analysis. The etching study was done to reveal the dislocations in the crystal which in turn explains mechanoluminescence emission. The mechanoluminescence property exhibited by the crystal makes it suitable for stress sensing applications. Besides being a centrosymmetric crystal, it also exhibits NLO behavior. Dielectric properties were studied and theoretical calculations of Fermi energy, valence electron plasma energy, penn gap and polarisability have been done.

Strong Electro‐Optic Effect and Spontaneous Domain Formation in Self‐Assembled Peptide Structures

PubMed Central

Lafargue, Clément; Handelman, Amir; Shimon, Linda J. W.; Rosenman, Gil; Zyss, Joseph

2017-01-01

Short peptides made from repeating units of phenylalanine self‐assemble into a remarkable variety of micro‐ and nanostructures including tubes, tapes, spheres, and fibrils. These bio‐organic structures are found to possess striking mechanical, electrical, and optical properties, which are rarely seen in organic materials, and are therefore shown useful for diverse applications including regenerative medicine, targeted drug delivery, and biocompatible fluorescent probes. Consequently, finding new optical properties in these materials can significantly advance their practical use, for example, by allowing new ways to visualize, manipulate, and utilize them in new, in vivo, sensing applications. Here, by leveraging a unique electro‐optic phase microscopy technique, combined with traditional structural analysis, it is measured in di‐ and triphenylalanine peptide structures a surprisingly large electro‐optic response of the same order as the best performing inorganic crystals. In addition, spontaneous domain formation is observed in triphenylalanine tapes, and the origin of their electro‐optic activity is unveiled to be related to a porous triclinic structure, with extensive antiparallel beta‐sheet arrangement. The strong electro‐optic response of these porous peptide structures with the capability of hosting guest molecules opens the door to create new biocompatible, environmental friendly functional materials for electro‐optic applications, including biomedical imaging, sensing, and optical manipulation. PMID:28932664

Effect of gamma irradiation on the structural, mechanical and optical properties of polytetrafluoroethylene sheet

NASA Astrophysics Data System (ADS)

Mohammadian-Kohol, M.; Asgari, M.; Shakur, H. R.

2018-04-01

In this study, the effects of gamma radiation on the chemical structure, mechanical and optical properties of polytetrafluoroethylene (PTFE) sheet were investigated with various doses up to 12 kGy. The chemical changes in the structure were studied by FTIR spectroscopy. Also, effects of radiation on the different mechanical parameters such as Young's modulus, toughness, strain, and stress were studied at the maximum tolerable force and the fracture points. Furthermore, changing the various optical parameters such as absorption coefficient, Urbach energy, optical band gaps, refractive index, optical dispersion parameters and plasma resonance frequency were studied by UV-visible spectroscopy. Formation of a band at 1594 cm-1, which was belonged to double carbon bonds, indicated that chain-scission was occurred at 12 kGy gamma irradiation dose. As well, the mechanical results showed an increase in the elastic behavior of PTFE sheets and a decrease in the plastic behavior of it with absorbed dose increasing. Moreover, the results showed that gamma irradiation can effectively change the various optical properties of PTFE sheets due to different phenomena such as degradation of the main chains, occurring chain-scission, formation of free radicals and cross-linking in the polymer structure.

Variation in the structure and optical properties of gamma-irradiated Vanadyl 2,3-naphthalocyanine (VONc) nanostructure films

NASA Astrophysics Data System (ADS)

Darwish, A. A. A.; Issa, Shams A. M.

2018-07-01

Naphthalocyanines have an important optical and electrical property, made it eligible to be a key utilitarian materials for a couple of special applications. Therefore, this study focused on the influence of gamma rays irradiation on the structure and optical properties of Vanadyl 2,3-naphthalocyanine (VONc) films. The VONc films have been prepared using the thermal evaporating technique. The investigated films were irradiated with gamma-rays 20, 40 and 60 kGy doses. X-ray diffraction exhibited that the as-deposited VONc films have nanostructure nature, which changed to the amorphous structure with gamma-rays radiation dosage. The optical results indicate that the optical absorption mechanism complied with the indirect allowed transition. It was observed also, there were no prominent changes found in the energy gap values when VONc films were exposed to gamma radiation. However, the optical conductivity rises with additional amounts of gamma-ray dose. This behavior may be attributed to the addition of electrons which freed by the incident photon energy because of a few changes in the film structure caused by the gamma-ray radiation. These outcomes illustrated that VONc films own the characteristics to be utilized in the field of optoelectronic applications.

Electronic band structures and optical properties of type-II superlattice photodetectors with interfacial effect.

PubMed

Qiao, Peng-Fei; Mou, Shin; Chuang, Shun Lien

2012-01-30

The electronic band structures and optical properties of type-II superlattice (T2SL) photodetectors in the mid-infrared (IR) range are investigated. We formulate a rigorous band structure model using the 8-band k · p method to include the conduction and valence band mixing. After solving the 8 × 8 Hamiltonian and deriving explicitly the new momentum matrix elements in terms of envelope functions, optical transition rates are obtained through the Fermi's golden rule under various doping and injection conditions. Optical measurements on T2SL photodetectors are compared with our model and show good agreement. Our modeling results of quantum structures connect directly to the device-level design and simulation. The predicted doping effect is readily applicable to the optimization of photodetectors. We further include interfacial (IF) layers to study the significance of their effect. Optical properties of T2SLs are expected to have a large tunable range by controlling the thickness and material composition of the IF layers. Our model provides an efficient tool for the designs of novel photodetectors.

Electronic Structure, Optical and Transport Properties of Double Perovskite La2NbMnO6: A Theoretical Understanding from DFT Calculations

NASA Astrophysics Data System (ADS)

Parrey, Khursheed Ahmad; Khandy, Shakeel Ahmad; Islam, Ishtihadah; Laref, Amel; Gupta, Dinesh C.; Niazi, Asad; Aziz, Anver; Ansari, S. G.; Khenata, R.; Rubab, Seemin

2018-03-01

Double perovskite La2NbMnO6 was systematically studied using the first-principles calculations. The structural, electronic, optical and transport properties of this compound were calculated. Spin resolved band structure predicted this material as a half-metal with an energy gap of 3.75 eV in spin down state. The optical coefficients including optical conductivity, reflectivity and electron energy loss are calculated for photon energy up to 30.00 eV to understand the optical response of this perovskite. The strong absorption of all the ultraviolet and infrared frequencies of the spectrum by this material may suggest the potential application of this material for the optoelectronic devices in ultraviolet and infra-red region. Also, the thermoelectric properties with a speculation from the half-metallic electronic structure are reported. Subsequently, the Seebeck coefficient, electrical and thermal conductivity coefficients are calculated to predict the thermoelectric figure of merit (zT), the maximum of which is found out to be 0.14 at 800 K.

Optical and sensing properties of sol-gel derived vanadium pentoxide thin films with porous and dense structures

NASA Astrophysics Data System (ADS)

Babeva, T.; Awala, H.; Grand, J.; Lazarova, K.; Vasileva, M.; Mintova, S.

2018-03-01

The sol-gel and spin-coating methods were used for deposition of thin transparent V2O5 films on optical glass substrates and silicon wafers. Different synthesis and deposition conditions, including synthesis temperatures and post-deposition annealing, were used aiming at obtaining transparent films with high refractive index and good optical quality. The surface morphology and structure of the films were studied by SEM and XRD. The optical properties (refractive index, extinction coefficient and optical band gap) and thickness of the V2O5 films were determined from their transmittance and reflectance spectra. The potential application of the films as building blocks of optical sensors was demonstrated by preparation of multilayered structures comprising both V2O5 and BEA-type zeolite films and testing their response towards acetone vapors.

Structural and optical properties of nano-structured CdS thin films prepared by chemical bath deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Rekha, E-mail: rekha.mittal07@gmail.com; Kumar, Dinesh; Chaudhary, Sujeet

2016-05-06

Cadmium sulfide (CdS) thin films have been deposited on conducting glass substrates by chemical bath deposition (CBD) technique. The effect of precursor concentration on the structural, morphological, compositional, and optical properties of the CdS films has been studied. Crystal structure of these CdS films is characterized by X-ray diffraction (XRD) and it reveals polycrystalline structure with mixture of cubic and wurtzite phases with grain size decreasing as precursor concentration is increased. Optical studies reveal that the CdS thin films have high transmittance in visible spectral region reaching 90% and the films possess direct optical band gap that decreases from 2.46more » to 2.39 eV with decreasing bath concentration. Our study suggests that growth is nucleation controlled.« less

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

NASA Astrophysics Data System (ADS)

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.

Study the structural and optical behaviour of polyaniline/ZrO2 nanocomposites

NASA Astrophysics Data System (ADS)

Sidhu, Gaganpreet Kaur; Kumar, Naresh; Kumar, Rajesh

2018-05-01

In nanoscience, hybrid material based on polymer and nanoparticles are of great interest because of much improved properties of components. Polymers are of enormous interest because of their various properties like flexibility, low weight and easy processing. Here, we studied the influence of ZrO2 nanoparticles on the structural and optical properties of Polyaniline (PANI). ZrO2 mixed with PANI, improve its structural and optical properties. XRD studies reveal that ZrO2 nanoparticles exist in the tetragonal phase in ZrO2/PANI nanocomposites. UV-Vis spectroscopic studies have been carried out to understand the presence of various energy levels and their involvement in absorbance of light. In PANI nanocomposites, aniline monomer attach with ZrO2 nanoparticles through p-p stacking interaction, Vander waal force and hydrogen bonding interaction.

Effects of 200 keV Ar-ions irradiation on the structural and optical properties of reactively sputtered CrN films

NASA Astrophysics Data System (ADS)

Novaković, M.; Popović, M.; Zhang, K.; Rakočević, Z.; Bibić, N.

2016-12-01

Modification in structural and optical properties of chromium-nitride (CrN) films induced by argon ion irradiation and thermal annealings were investigated using various experimental techniques. CrN films deposited by d. c. reactive sputtering on Si substrate were implanted with 200 keV argon ions, at fluences of 5-20 × 1015 ions/cm2. As-implanted samples were then annealed in vacuum, for 2 h at 700 °C. Rutherford backscattering spectrometry, X-ray diffraction, cross-sectional (high-resolution) transmission electron microscopy and spectroscopic ellipsometry (SE) measurements were carried out in order to study structural and optical properties of the layers. After irradiation with 200 keV Ar ions a damaged surface layer of nanocrystalline structure was generated, which extended beyond the implantation profile, but left an undamaged bottom zone. Partial loss of columnar structure observed in implanted samples was recovered after annealing at 700 °C and CrN started to decompose to Cr2N. This layer geometry determined from transmission electron microscopy was inferred in the analysis of SE data using the combined Drude and Tauc-Lorentz model, and the variation of the optical bandgap was deduced. The results are discussed on the basis of the changes induced in the microstructure. It was found that the optical properties of the layers are strongly dependent on the defects' concentration of CrN.

Electronic structures and magnetic/optical properties of metal phthalocyanine complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baba, Shintaro; Suzuki, Atsushi, E-mail: suzuki@mat.usp.ac.jp; Oku, Takeo

2016-02-01

Electronic structures and magnetic / optical properties of metal phthalocyanine complexes were studied by quantum calculations using density functional theory. Effects of central metal and expansion of π orbital on aromatic ring as conjugation system on the electronic structures, magnetic, optical properties and vibration modes of infrared and Raman spectra of metal phthalocyanines were investigated. Electron and charge density distribution and energy levels near frontier orbital and excited states were influenced by the deformed structures varied with central metal and charge. The magnetic parameters of chemical shifts in {sup 13}C-nuclear magnetic resonance ({sup 13}C-NMR), principle g-tensor, A-tensor, V-tensor of electricmore » field gradient and asymmetry parameters derived from the deformed structures with magnetic interaction of nuclear quadruple interaction based on electron and charge density distribution with a bias of charge near ligand under crystal field.« less

Au10(SG)10: A Chiral Gold Catenane Nanocluster with Zero Confined Electrons. Optical Properties and First-Principles Theoretical Analysis.

PubMed

Bertorelle, Franck; Russier-Antoine, Isabelle; Calin, Nathalie; Comby-Zerbino, Clothilde; Bensalah-Ledoux, Amina; Guy, Stephan; Dugourd, Philippe; Brevet, Pierre-François; Sanader, Željka; Krstić, Marjan; Bonačić-Koutecký, Vlasta; Antoine, Rodolphe

2017-05-04

We report facile synthesis of the Au 10 (SG) 10 nanoclusters, where SG stands for glutathione, found to be promising as a new class of radiosensitizers for cancer radiotherapy. The homoleptic catenane structure with two Au 5 SG 5 interconnected rings, among different isomer structures, gives the best agreement between theoretical and experimental optical spectra and XRD patterns. This catenane structure exhibits a centrosymmetry-broken structure, resulting in enhanced second harmonic response and new characteristic circular dichroism signals in the spectral region of 250-400 nm. This is the first determination of the nonlinear optical properties of a ligated cluster with an equal Au-to-ligand ratio, thus without a metallic core and therefore zero confined electrons. Insight into the nonlinear and chiroptical efficiencies arising from interplay between structural and electronic properties is provided by the TD-DFT approach.

Handbook of the Properties of Optical Materials

DTIC Science & Technology

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

Optical filtering and luminescence property of some molybdates prepared by combustion synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, P. J., E-mail: yadav.pooja75@yahoo.in; Joshi, C. P.; Moharil, S. V., E-mail: svmoharil@yahoo.com

2014-10-15

As an important class of lanthanide inorganic compounds, rare earth ions doped molybdates have gained much attention due to their attractive luminescence and structural properties, supporting various promising applications as phosphor materials in the fields such as white light-emitting diodes, optical fibers, biolabel, lasers, and so on. The molybdate family has promising trivalent cation conducting properties and most of the optical properties result from electron transitions of the 4f shell, which are greatly affected by the composition and structures of rare-earth compounds. In this paper we report the molybdate CaMoO{sub 4}:Eu{sup 3+} for red SSL and Bi{sub 1.4}Y{sub 0.6}MoO{sub 6},more » Y{sub 6}MoO{sub 12} for optical filtering, prepared by one step combustion synthesis.« less

Elemental, morphological, structural, optical, and magnetic properties of erbium doped ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Poornaprakash, B.; Chalapathi, U.; Purusottam Reddy, B.; Prabhakar Vattikuti, S. V.; Siva Pratap Reddy, M.; Park, Si-Hyun

2018-03-01

The sensible tuning of the structural, optical, and magnetic properties of ZnO nanoparticles (NPs) with suitable doping can enhance their applicability in diverse fields. In this study, we synthesized ZnO NPs with Er (0-4 at%) doping and their elemental, structural, optical, and magnetic properties were studied. Both field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) studies of the suspensions consist of hexagonal shaped NPs. All the prepared NPs exhibited hexagonal phase as demonstrated by powder x-ray diffraction studies. A blue shift was observed in the Er doped ZnO NPs compared to pure ZnO, indicating the increased optical bandgap. Vibrating sample magnetometer studies exhibited the pure ZnO NPs was typical diamagnetic feature whereas all the Er doped ZnO NPs were paramagnetic feature at 300 K. This is the first paramagnetic report on Er doped ZnO NPs.

Effect of rapid thermal annealing on the electrical, optical and structural properties of ZnO-doped In2O3 films grown by linear facing target sputtering.

PubMed

Cho, Chung-Ki; Kim, Han-Ki

2012-04-01

We investigated the effect of rapid thermal annealing on the electrical, optical, and structural properties of ZnO-doped In2O3 (ZIO) films grown at different Ar/O2 flow ratios (15/0 and 15/1 sccm) by using linear facing target sputtering. It was found that the ZIO films grown at different Ar/O2, flow ratios showed different electrical and optical behavior with increasing rapid thermal annealing temperature. Synchrotron X-ray scattering examination showed that the different electrical and optical properties of the ZIO films could be attributed to the difference in preferred orientation with an increase in rapid thermal annealing temperature.

Time-domain separation of optical properties from structural transitions in resonantly bonded materials.

PubMed

Waldecker, Lutz; Miller, Timothy A; Rudé, Miquel; Bertoni, Roman; Osmond, Johann; Pruneri, Valerio; Simpson, Robert E; Ernstorfer, Ralph; Wall, Simon

2015-10-01

The extreme electro-optical contrast between crystalline and amorphous states in phase-change materials is routinely exploited in optical data storage and future applications include universal memories, flexible displays, reconfigurable optical circuits, and logic devices. Optical contrast is believed to arise owing to a change in crystallinity. Here we show that the connection between optical properties and structure can be broken. Using a combination of single-shot femtosecond electron diffraction and optical spectroscopy, we simultaneously follow the lattice dynamics and dielectric function in the phase-change material Ge2Sb2Te5 during an irreversible state transformation. The dielectric function changes by 30% within 100 fs owing to a rapid depletion of electrons from resonantly bonded states. This occurs without perturbing the crystallinity of the lattice, which heats with a 2-ps time constant. The optical changes are an order of magnitude larger than those achievable with silicon and present new routes to manipulate light on an ultrafast timescale without structural changes.

Optical Properties of Multilayer CdSe/POLYMER Structures

NASA Astrophysics Data System (ADS)

Red'Ko, V. P.; Voitenkov, A. I.; Kovalenko, O. E.

The effects of preparation condition, concentration and size of particles upon optical and photoelectrical characteristics of multilayer structures CdSe/polyethylene terephthalate obtained by electron-beam evaporation were investigated.

Microfiber Optical Sensors: A Review

PubMed Central

Lou, Jingyi; Wang, Yipei; Tong, Limin

2014-01-01

With diameter close to or below the wavelength of guided light and high index contrast between the fiber core and the surrounding, an optical microfiber shows a variety of interesting waveguiding properties, including widely tailorable optical confinement, evanescent fields and waveguide dispersion. Among various microfiber applications, optical sensing has been attracting increasing research interest due to its possibilities of realizing miniaturized fiber optic sensors with small footprint, high sensitivity, fast response, high flexibility and low optical power consumption. Here we review recent progress in microfiber optical sensors regarding their fabrication, waveguide properties and sensing applications. Typical microfiber-based sensing structures, including biconical tapers, optical gratings, circular cavities, Mach-Zehnder interferometers and functionally coated/doped microfibers, are summarized. Categorized by sensing structures, microfiber optical sensors for refractive index, concentration, temperature, humidity, strain and current measurement in gas or liquid environments are reviewed. Finally, we conclude with an outlook for challenges and opportunities of microfiber optical sensors. PMID:24670720

Z-scan measurement for nonlinear absorption property of rGO/ZnO:Al thin film

NASA Astrophysics Data System (ADS)

Sreeja, V. G.; Anila, E. I.

2018-04-01

We report the fabrication of reduced graphene oxide integrated aluminium doped zinc oxide (rGO/ZnO:Al) composite thin film on a glass substrate by spin coating technique. The effect of rGO on structural and linear optical properties of rGO/ZnO:Al composite thin film was explored with the help of X-Ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-Vis absorption spectroscopy. Structural studies reveals that the composite film has hexagonal wurtzite structure with a strong bonding between rGO and ZnO:Al material. The band gap energy of ZnO:Al thin film was red shifted by the addition of rGO. The Nonlinear absorption property was investigated by open aperture Z-scan technique by using Q switched Nd-YAG laser at 532nm. The Z-scan results showed that the composite film demonstrates reverse saturable absorption property with a nonlinear absorption coefficient, β, of 12.75×10-7m/w. The results showed that investigated rGO/ZnO:Al thin film is a promising material suitable for the applications in absorbing type optical devices such as optical limiters, optical switches and protection of the optical sensors in the field of nonlinear optics.

Effect of Mo and Ti doping concentration on the structural and optical properties of ZnS nanoparticles

NASA Astrophysics Data System (ADS)

Naz, Hina; Ali, Rai Nauman; Zhu, Xingqun; Xiang, Bin

2018-06-01

In this paper, we report the effect of single phase Mo and Ti doping concentration on the structural and optical properties of the ZnS nanoparticles. The structural and optical properties of the as-synthesized samples have been examined by x-ray diffraction, transmission electron microscopy (TEM), UV-visible near infrared absorption spectroscopy and x-ray photoelectron spectroscopy. TEM characterizations reveal a variation in the doped ZnS nanoparticle size distribution by utilizing different dopants of Mo and Ti. In absorption spectra, a clear red shift of 14 nm is observed with increasing Mo concentration as compared to pure ZnS nanoparticles, while by increasing Ti doping concentration, blue shift of 14 nm is obtained. Moreover, it demonstrates that the value of energy band gap decreases from 4.03 eV to 3.89 eV in case of Mo doping. However, the value of energy band gap have shown a remarkable increase from 4.11 eV to 4.27 eV with increasing Ti doping concentration. Our results provide a new pathway to understand the effect of Mo and Ti doping concentrations on the structural and optical properties of ZnS nanoparticles as it could be the key to tune the properties for future optoelectronic devices.

Magnetic and optical properties of carbon and silicon decorated free standing buckled germanene: A DFT approach

NASA Astrophysics Data System (ADS)

Dhar, Namrata; Jana, Debnarayan

2018-04-01

Ab initio magnetic and optical properties of group IV elements (carbon (C) and silicon (Si)) decorated free standing (FS) buckled germanene systems have been employed theoretically. Our study elucidates that, decoration of these elements in proper sites with suitable concentrations form dynamically stable configurations. Band structure is modified due to decoration of these atoms in Ge-nanosheet and pristine semi-metallic germanene undergoes to semiconductors with a finite amount of bandgap. Interestingly, this bandgap value meets closely the requirement of gap for field effect transistor (FET) applications. Moreover, significant magnetic moment is induced in non-magnetic germanene for C decorated structure and ground state in anti-ferromagnetic in nature for this structure. Along with magnetic property, optical properties like dielectric functions, optical absorption, electron energy loss spectra (EELS), refractive index and reflectivity of these systems have also been investigated. Maximum number of plasma frequencies appear for Si decorated configuration considering both parallel and perpendicular polarizations. In addition, birefringence characteristics of these configurations have also been studied as it is an important parameter in various applications of optical devices, liquid crystal displays, light modulators etc.

Theoretical investigation of structural, electronic and optical properties of MgxBa1-xS, MgxBa1-xSe and MgxBa1-xTe ternary alloys using DFT based FP-LAPW approach

NASA Astrophysics Data System (ADS)

Bhattacharjee, Rahul; Chattopadhyaya, Surya

2017-11-01

Density functional theory (DFT) based full-potential linearized augmented plane wave (FP-LAPW) methodology has been employed to investigate theoretically the structural, electronic and optical properties of MgxBa1-xS, MgxBa1-xSe and MgxBa1-xTe ternary alloys for 0 ≤ x ≤ 1 in their rock-salt (B1) crystallographic phase. The exchange-correlation potentials for the structural properties have been computed using the Wu-Cohen generalized-gradient approximation (WC-GGA) scheme, while those for the electronic and optical properties have been computed using both the WC-GGA and the recently developed Tran-Blaha modified Becke-Johnson (TB-mBJ) schemes. The thermodynamic stability of all the ternary alloys have been investigated by calculating their respective enthalpy of formation. The atomic and orbital origin of different electronic states in the band structure of the compounds have been identified from the respective density of states (DOS). Using the approach of Zunger and co-workers, the microscopic origin of band gap bowing has been discussed in term of volume deformation, charge exchange and structural relaxation. Bonding characteristics among the constituent atoms of each of the specimens have been discussed from their charge density contour plots. Optical properties of the binary compounds and ternary alloys have been investigated theoretically in terms of their respective dielectric function, refractive index, normal incidence reflectivity and optical conductivity. Several calculated results have been compared with available experimental and other theoretical data.

Optical and acoustic metamaterials: superlens, negative refractive index and invisibility cloak

NASA Astrophysics Data System (ADS)

Wong, Zi Jing; Wang, Yuan; O'Brien, Kevin; Rho, Junsuk; Yin, Xiaobo; Zhang, Shuang; Fang, Nicholas; Yen, Ta-Jen; Zhang, Xiang

2017-08-01

Metamaterials are artificially engineered materials that exhibit novel properties beyond natural materials. By carefully designing the subwavelength unit cell structures, unique effective properties that do not exist in nature can be attained. Our metamaterial research aims to develop new subwavelength structures with unique physics and experimentally demonstrate unprecedented properties. Here we review our research efforts in optical and acoustic metamaterials in the past 15 years which may lead to exciting applications in communications, sensing and imaging.

A Study on the Plasmonic Properties of Silver Core Gold Shell Nanoparticles: Optical Assessment of the Particle Structure

NASA Astrophysics Data System (ADS)

Mott, Derrick; Lee, JaeDong; Thi Bich Thuy, Nguyen; Aoki, Yoshiya; Singh, Prerna; Maenosono, Shinya

2011-06-01

This paper reports a qualitative comparison between the optical properties of a set of silver core, gold shell nanoparticles with varying composition and structure to those calculated using the Mie solution. To achieve this, silver nanoparticles were synthesized in aqueous phase from a silver hydroxide precursor with sodium acrylate as dual reducing-capping agent. The particles were then coated with a layer of gold with controllable thickness through a reduction-deposition process. The resulting nanoparticles reveal well defined optical properties that make them suitable for comparison to ideal calculated results using the Mie solution. The discussion focuses on the correlation between the synthesized core shell nanoparticles with varying Au shell thickness and the Mie solution results in terms of the optical properties. The results give insight in how to design and synthesize silver core, gold shell nanoparticles with controllable optical properties (e.g., SPR band in terms of intensity and position), and has implications in creating nanoparticle materials to be used as biological probes and sensing elements.

Understanding luminescence properties of grain boundaries in GaN thin films and their atomistic origin

NASA Astrophysics Data System (ADS)

Yoo, Hyobin; Yoon, Sangmoon; Chung, Kunook; Kang, Seoung-Hun; Kwon, Young-Kyun; Yi, Gyu-Chul; Kim, Miyoung

2018-03-01

We report our findings on the optical properties of grain boundaries in GaN films grown on graphene layers and discuss their atomistic origin. We combine electron backscatter diffraction with cathodoluminescence to directly correlate the structural defects with their optical properties, enabling the high-precision local luminescence measurement of the grain boundaries in GaN films. To further understand the atomistic origin of the luminescence properties, we carefully probed atomic core structures of the grain boundaries by exploiting aberration-corrected scanning transmission electron microscopy. The atomic core structures of grain boundaries show different ordering behaviors compared with those observed previously in threading dislocations. Energetics of the grain boundary core structures and their correlation with electronic structures were studied by first principles calculation.

Structural, morphological, and optical study of titania-based nanopowders suitable for photocatalytic applications

NASA Astrophysics Data System (ADS)

Šćepanović, M.; Grujić-Brojčin, M.; Abramović, B.; Golubović, A.

2017-01-01

Systematic investigation of the relationship between structural, morphological, optical and photocatalytic properties of the titania-based nanopowders is presented. A series of pure and doped titania catalysts with various (anatase and brookite) phase compositions have been prepared by sol-gel or hydrothermal route. The crystal structure and composition of the synthesized samples have been extensively characterised by XRD and Raman scattering measurements. The nanopowder morphology has been studied using microscopic methods (SEM, AFM, and STM), whereas the porous structure has been revealed by the analysis of nitrogen sorption data. The optical and electronic properties have been studied by spectroscopic ellipsometry. All investigated properties have been correlated to photocatalytic activity, tested in degradation of the pharmaceutically active substances (such as metoprolol and alprazolam) induced by UVA or visible radiation. Based on this correlation, the physical properties which contribute most to the increase in photocatalytic activity of synthesized nanopowders have been determined, in order to optimize the synthesis conditions which could lead to the maximal efficiency in degradation of particular pollutant.

Electronic structure and optical properties of metal doped tetraphenylporphyrins

NASA Astrophysics Data System (ADS)

Shah, Esha V.; Roy, Debesh R.

2018-05-01

A density functional scrutiny on the structure, electronic and optical properties of metal doped tetraphenylporphyrins MTPP (M=Fe, Co, Ni) is performed. The structural stability of the molecules is evaluated based on the electronic parameters like HOMO-LUMO gap (HLG), chemical hardness (η) and binding energy of the central metal atom to the molecular frame etc. The computed UltraViolet-Visible (UV-Vis) optical absorption spectra for all the compounds are also compared. The molecular structures reported are the lowest energy configurations. The entire calculations are carried out with a widely reliable functional, viz. B3LYP with a popular basis set which includes a scaler relativistic effect, viz. LANL2DZ.

Learning about Structural and Optical Properties of Organic Compounds through Preparation of Functional Nanomicelles While Avoiding Hazardous Chemicals or Complicated Apparatus

ERIC Educational Resources Information Center

Langhals, Heinz; Eberspa¨cher, Moritz; Hofer, Alexander

2015-01-01

The synthesis of nanomicelles in the aqueous phase on the basis of nonhazardous detergents is described where azulene and a naphthalene tetracarboximide are used in this experiment to teach the relation between structural and optical properties of organic compounds and point out possible applications. The experiment covers many aspects of…

CoBOP: Microbial Biofilms: A Parameter Altering the Apparent Optical Properties of Sediments, Seagrasses and Surfaces

DTIC Science & Technology

2002-09-30

CoBOP: Microbial Biofilms: A Parameter Altering the Apparent Optical Properties of Sediments, Seagrasses and Surfaces Alan W. Decho Department...TITLE AND SUBTITLE CoBOP: Microbial Biofilms: A Parameter Altering the Apparent Optical Properties of Sediments, Seagrasses and Surfaces 5a. CONTRACT...structures produced by bacteria. Their growth appears to depend on biofilm processes and light distributions ( photosynthesis ). Therefore, the data acquired

DFT-BASED AB INITIO STUDY OF THE ELECTRONIC AND OPTICAL PROPERTIES OF CESIUM BASED FLUORO-PEROVSKITE CsMF3 (M = Ca AND Sr)

NASA Astrophysics Data System (ADS)

Harmel, M.; Khachai, H.; Ameri, M.; Khenata, R.; Baki, N.; Haddou, A.; Abbar, B.; UǦUR, Ş.; Omran, S. Bin; Soyalp, F.

2012-12-01

Density functional theory (DFT) is performed to study the structural, electronic and optical properties of cubic fluoroperovskite AMF3 (A = Cs; M = Ca and Sr) compounds. The calculations are based on the total-energy calculations within the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential is treated by local density approximation (LDA) and generalized gradient approximation (GGA). 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 calculations of the electronic band structure, density of states and charge density reveal that compounds are both ionic insulators. The optical properties (namely: the real and the imaginary parts of the dielectric function ɛ(ω), the refractive index n(ω) and the extinction coefficient k(ω)) were calculated for radiation up to 40.0 eV.

Further Insights on the Chemical Structure of Humic Substances (HS) and Chromophoric Dissolved Organic Matter (CDOM) in Relation to their Optical/Chemical Properties

NASA Astrophysics Data System (ADS)

Del Vecchio, R.; Schendorf, T. M.; Koech, K.; Blough, N. V.

2016-02-01

HS have been studied extensively over the last decades, yet the structural basis of their optical properties is still highly debated. Aromatic ketones, aldehydes and quinones along with carboxylic groups and phenolic moieties are significant constituents of HS, however their contribution to the optical properties has only recently been investigated. Chemical manipulation of selected functional groups thus represents an extremely promising approach to highlight the contribution of such groups to the HS (and CDOM) optical properties. Chemical reduction (and re-oxidation) along with pH titrations are employed herein to assess the relative contribution of aromatic ketones/aldehydes/quinones and carboxylic groups/phenolic moieties, respectively to the optical properties of HS (and CDOM). Results indicate that (a) the contribution of quinones to HS absorption and fluorescence is minor (or nil), while that of aromatic ketones (and aldehydes) is significant; (b) phenolic groups contribute more than carboxylic acids to the HS optical properties; (c) the effects of borohydride reduction and pH on the long-wavelength absorption and fluorescence is consistent with charge-transfer interactions between carbonyl and phenolic groups (as well as aromatic carboxylic acids, but to a smaller extent). Results will be presented within the context of our proposed charge-transfer model.

In Situ Identification of Nanoparticle Structural Information Using Optical Microscopy.

PubMed

Culver, Kayla S B; Liu, Tingting; Hryn, Alexander J; Fang, Ning; Odom, Teri W

2018-05-11

Diffraction-limited optical microscopy lacks the resolution to characterize directly nanoscale features of single nanoparticles. This paper describes how surprisingly rich structural features of small gold nanostars can be identified using differential interference contrast (DIC) microscopy. First, we established a library of structure-property relationships between nanoparticle shape and DIC optical image and then validated the correlation with electrodynamic simulations and electron microscopy. We found that DIC image patterns of single nanostars could be differentiated between 2D and 3D geometries. Also, DIC images could elucidate the symmetry properties and orientation of nanoparticles. Finally, we demonstrated how this wide-field optical technique can be used for in situ characterization of single nanoparticles rotating at a glass-water interface.

Influence of ordering change on the optical and thermal properties of inflation polyethylene films

NASA Astrophysics Data System (ADS)

Morikawa, Junko; Orie, Akihiro; Hikima, Yuta; Hashimoto, Toshimasa; Juodkazis, Saulius

2011-04-01

Changes of thermal diffusivity inside femtosecond laser-structured volumes as small as few percent were reliably determined (with standard deviation less than 1%) with miniaturized sensors. An increase of thermal diffusivity of a crystalline high-density polyethylene (HDPE) inflation films by 10-20% from the measured (1.16 ± 0.01) × 10 -7 m 2 s -1 value in regions not structured by femtosecond laser pulses is considerably larger than that of non-crystalline polymers, 0-3%. The origin of the change of thermal diffusivity are interplay between the laser induced disordering, voids' formation, compaction, and changes in molecular orientation. It is shown that laser structuring can be used to modify thermal and optical properties. The birefringence and infrared spectroscopy with thermal imaging of CH 2 vibrations are confirming inter-relation between structural, optical, and thermal properties of the laser-structured crystalline HDPE inflation films. Birefringence modulation as high as Δ n ˜ ± 1 × 10 -3 is achieved with grating structures.

Near-infrared radiation absorption properties of covellite (CuS) using first-principles calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Lihua, E-mail: xiaolihua@git.edu.cn; College of Physics and Information Science, Hunan Normal University, Changsha 410081; Guizhou Special Functional Materials 2011 Collaborative Innovation Center, Guizhou Institute of Technology, Guiyang 550003

2016-08-15

First-principles density functional theory was used to investigate the electronic structure, optical properties and the origin of the near-infrared (NIR) absorption of covellite (CuS). The calculated lattice constant and optical properties are found to be in reasonable agreement with experimental and theoretical findings. The electronic structure reveals that the valence and conduction bands of covellite are determined by the Cu 3d and S 3p states. By analyzing its optical properties, we can fully understand the potential of covellite (CuS) as a NIR absorbing material. Our results show that covellite (CuS) exhibits NIR absorption due to its metal-like plasma oscillation inmore » the NIR range.« less

Structural and optical characterization of NiSe film grown by screen-printing method

NASA Astrophysics Data System (ADS)

Sharma, Kapil; Sharma, D. K.; Dwivedi, D. K.; Kumar, Vipin

2018-05-01

In present investigation NiSe films were grown by economical screen-printing method. Optimum conditions for growing good quality screen-printed films were found. The films were characterized for their structural and optical properties. The polycrystalline nature of films with hexagonal structure was confirmed through XRD analysis. Direct type of optical band gap of 1.75 eV for the NiSe film was confirmed by optical characterization.

Effect of Hydrostatic Pressure on the Structural, Electronic and Optical Properties of SnS2 with a Cubic Structure: The DFT Approach

NASA Astrophysics Data System (ADS)

Bakhshayeshi, A.; Taghavi Mendi, R.; Majidiyan Sarmazdeh, M.

2018-02-01

Recently, a cubic structure of polymorphic SnS2 has been synthesized experimentally, which is stable at room temperature. In this paper, we calculated some structural, electronic and optical properties of the cubic SnS2 structure based on the full potential-linearized augmented plane waves method. We also studied the effect of hydrostatic pressure on the physical properties of the cubic SnS2 structure. Structural results show that the compressibility of the cubic SnS2 phase is greater than its trigonal phase and the compressibility decreases with increasing pressure. Investigations of the electronic properties indicate that pressure changes the density of states and the energy band gap increases with increasing pressure. The variation of energy band gap versus pressure is almost linear. We concluded that cubic SnS2 is a semiconductor with an indirect energy band gap, like its trigonal phase. The optical calculations revealed that the dielectric constant decreases with increasing pressure, and the width of the forbidden energy interval increases for electromagnetic wave propagation. Moreover, plasmonic energy and refractive index are changed with increasing pressure.

Investigation of the electronic, magnetic and optical properties of {\\sf Co}_{\\sf 2}{\\sf CrZ} (Z = Si, Ge) under pressure—a density functional theory study

NASA Astrophysics Data System (ADS)

Seema, K.; Kumar, Ranjan

2014-01-01

The structural, electronic, magnetic and optical properties of Co-based Heusler compounds, Co2CrZ (Z = Si, Ge), are studied using first-principle density functional theory. The calculations are performed within the generalized gradient approximation. Our calculated structural parameters at 0 GPa agree well with previous available results. The calculated magnetic moment agrees well with the Slater-Pauling (SP) rule. We have studied the effect of pressure on the electronic and magnetic properties of Co2CrSi and Co2CrGe. With an increase in applied pressure, a decrease in cell volume is observed. Under application of external pressure, the valence band and conduction band are shifted downward which leads to a modification of electronic structure. There exists an indirect band gap along Γ-X for both the alloys. Co2CrSi and Co2CrGe retain 100% spin polarization up to 60 and 50 GPa, respectively. The local magnetic moments of the Co and Si (Ge) atoms increase with an increase in pressure whereas the local magnetic moment of the Cr atom decreases. In addition, the optical properties such as dielectric function, absorption spectra, optical conductivity and energy loss function of these alloys have also been investigated. To our knowledge this is the first theoretical prediction of the pressure dependence of the structural, electronic, magnetic and optical properties of Co2CrSi and Co2CrGe.

Ab initio studies of structural, electronic, optical, elastic and thermal properties of silver gallium dichalcogenides (AgGaX{sub 2}: X = S, Se, Te)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Sheetal; Department of Physics, Panjab University, Chandigarh 160014; Verma, A.S., E-mail: ajay_phy@rediffmail.com

2014-05-01

Graphical abstract: - Highlights: • FP-LAPW method has been used to compute the solid state properties of AgGaX{sub 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{sub 2}: X = S, Se, Te). In this study, we have used the accurate full potentialmore » linearized augmented plane wave (FP-LAPW) method to find the equilibrium structural parameters and to compute the six elastic constants (C{sub 11}, C{sub 12}, C{sub 13}, C{sub 33}, C{sub 44} and C{sub 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.« less

Tungsten-incorporation induced red-shift in the bandgap of gallium oxide thin films

NASA Astrophysics Data System (ADS)

Rubio, E. J.; Ramana, C. V.

2013-05-01

Tungsten (W) incorporated Ga2O3 films were produced by co-sputter deposition. W-concentration was varied by the applied sputtering-power. The structure and optical properties of W-incorporated Ga2O3 films were evaluated using X-ray diffraction, scanning electron microscopy, and spectrophotometric measurements. No secondary phase formation was observed in W-incorporated Ga2O3 films. W-induced effects were significant on the structure and optical properties of Ga2O3 films. The bandgap of Ga2O3 films without W-incorporation was ˜5 eV. Red-shift in the bandgap was noted with increasing W-concentration indicating the electronic structure changes in W-Ga2O3 films. A functional relationship between W-concentration and optical property is discussed.

Effects on structural, optical, and magnetic properties of pure and Sr-substituted MgFe2O4 nanoparticles at different calcination temperatures

NASA Astrophysics Data System (ADS)

Loganathan, A.; Kumar, K.

2016-06-01

In the present work, pure and Sr2+ ions substituted Mg ferrite nanoparticles (NPs) had been prepared by co-precipitation method and their structural, optical, and magnetic properties at different calcination temperatures were studied. On this purpose, thermo gravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy, UV-Visible diffused reflectance spectroscopy, impedance spectroscopy, and vibrating sample magnetometer were carried out. The exo- and endothermic processes of synthesized precursors were investigated by TG-DTA measurements. The structural properties of the obtained products were examined by XRD analysis and show that the synthesized NPs are in the cubic spinel structure. The existence of two bands around 578-583 and 430-436 cm-1 in FT-IR spectrum also confirmed the formation of spinel-structured ferrite NPs. The lattice constants and particle size are estimated using XRD data and found to be strongly dependent on calcination temperatures. The optical, electrical, and magnetic properties of ferrite compositions also investigated and found to be strongly dependant on calcination temperatures.

GaAs monolayer: Excellent SHG responses and semi metallic to metallic transition modulated by vacancy effect

NASA Astrophysics Data System (ADS)

Rozahun, Ilmira; Bahti, Tohtiaji; He, Guijie; Ghupur, Yasenjan; Ablat, Abduleziz; Mamat, Mamatrishat

2018-05-01

Monolayer materials are considered as a promising candidate for novel applications due to their attractive magnetic, electronic and optical properties. Investigation on nonlinear optical (NLO) properties and effect of vacancy on monolayer materials are vital to property modulations of monolayers and extending their applications. In this work, with the aid of first-principles calculations, the crystal structure, electronic, magnetic, and optical properties of GaAs monolayers with the vacancy were investigated. The result shows gallium arsenic (GaAs) monolayer produces a strong second harmonic generation (SHG) response. Meanwhile, the vacancy strongly affects structural, electronic, magnetic and optical properties of GaAs monolayers. Furthermore, arsenic vacancy (VAs) brings semi metallic to metallic transition, while gallium vacancy (VGa) causes nonmagnetic to magnetic conversion. Our result reveals that GaAs monolayer possesses application potentials in Nano-amplifying modulator and Nano-optoelectronic devices, and may provide useful guidance in designing new generation of Nano-electronic devices.

Substrate temperature effect on structural and optical properties of Bi2Te3 thin films

NASA Astrophysics Data System (ADS)

Jariwala, B. S.; Shah, D. V.; Kheraj, Vipul

2012-06-01

Structural and optical properties of Bi2Te3 thin films, thermally evaporated on well-cleaned glass substrates at different substrate temperatures, are reported here. X-ray diffraction was carried out for the structural characterization. XRD patterns of the films exhibit preferential orientation along the [0 1 5] direction for the films deposited at all the substrate temperatures together with other supported planes [2 0 5] & [1 1 0]. All other deposition conditions like thickness, deposition rate and pressure were maintained same throughout the experiment. X-ray diffraction lines confirm that the grown films are polycrystalline in nature with hexagonal crystal structure. The effect of substrate temperature on lattice constants, grain size, micro strain, number of crystallites and dislocation density have been investigated and reported in this paper. Also the substrate temperature effect on the optical property has been also investigated using the FTIR spectroscopy.

Synthesis, structural and optical characterization of APbX{sub 3} (A=methylammonium, dimethylammonium, trimethylammonium; X=I, Br, Cl) hybrid organic-inorganic materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mancini, Alessandro; Quadrelli, Paolo; Amoroso, Giuseppe

2016-08-15

In this paper we report the synthesis, the crystal structure and the optical response of APbX{sub 3} (A=MA, DMA, and TMA; X=I, Br) hybrid organic-inorganic materials including some new phases. We observe that as the cation group increases in size, the optical absorption edge shifts to higher energies with energy steps which are systematic and independent on the anion. A linear correlation between the optical bad gap and the tolerance factor has been shown for the series of samples investigated. - Graphical abstract: The crystal structure and the optical response of the two series of hybrid organic-inorganic materials APbX{sub 3}more » (A=MA, DMA, and TMA; X=I, Br), which include some new phases, are reported. A dependence of crystal structure and band-gap with tolerance factor is shown. Display Omitted - Highlights: • DMAPbI{sub 3}, TMAPbI{sub 3} and TMAPbBr{sub 3} are reported as new hybrid organic-inorganic compounds. • Crystal structure and optical properties as a function of the number of methyl groups are provided. • Correlation between structure and optical properties are given as a function of tolerance factor.« less

The optical, vibrational, structural and elasto-optic properties of Zn{sub 0.25}Cd{sub 0.75}S{sub y}Se{sub 1-y} quaternary alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paliwal, U.; Swarkar, C. B., E-mail: chandrabhanuswarnkar@gmail.com; Sharma, M. D.

2016-05-06

The optical, vibrational, structural and elasto-optic properties of quaternary II-VI alloys Zn{sub 0.25}Cd{sub 0.75}S{sub 0.25}Se{sub 0.75}, Zn{sub 0.25}Cd{sub 0.75}S{sub 0.50}Se{sub 0.50} and Zn{sub 0.25}Cd{sub 0.75}S{sub 0.75}Se{sub 0.25} 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{sub 0}) and high frequency dielectric (ε{sub ∞}) constants are calculated to reveal optical behavior of alloys. The longitudinal ω{sub LO}(0) and transverse ω{sub TO}(0) optical frequencies are obtained to seemore » vibrational characteristics. Moreover, the elastic constants (c{sub ij}) 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.« less

Effect of cobalt doping on structural and optical properties of nanocrystalline La0.8Pb0.2CrO3 orthochromite

NASA Astrophysics Data System (ADS)

Zarrin, Naima; Shahidhusain

2018-04-01

We have synthesized nanocrystalline La0.8Pb0.2Cr1-xCoxO3 (0≤x≤0.3) through sol-gel process and studied their structural and optical properties. X-ray diffraction patterns reveal that the samples conform in the orthorhombic crystal symmetry with Pnma space group. Structural parameters are refined by Rietveld Refinement using Fullprof software. Lattice parameters and unit cell volume of doped samples are found to decrease with increase in Co doping. The optical energy band gapdecreases whereas Urbach energy increases with the increase in Co content.

Advances in optical structure systems; Proceedings of the Meeting, Orlando, FL, Apr. 16-19, 1990

NASA Astrophysics Data System (ADS)

Breakwell, John; Genberg, Victor L.; Krumweide, Gary C.

Various papers on advances in optical structure systems are presented. Individual topics addressed include: beam pathlength optimization, thermal stress in glass/metal bond with PR 1578 adhesive, structural and optical properties for typical solid mirror shapes, parametric study of spinning polygon mirror deformations, simulation of small structures-optics-controls system, spatial PSDs of optical structures due to random vibration, mountings for a four-meter glass mirror, fast-steering mirrors in optical control systems, adaptive state estimation for control of flexible structures, surface control techniques for large segmented mirrors, two-time-scale control designs for large flexible structures, closed-loop dynamic shape control of a flexible beam. Also discussed are: inertially referenced pointing for body-fixed payloads, sensor blending line-of-sight stabilization, controls/optics/structures simulation development, transfer functions for piezoelectric control of a flexible beam, active control experiments for large-optics vibration alleviation, composite structures for a large-optical test bed, graphite/epoxy composite mirror for beam-steering applications, composite structures for optical-mirror applications, thin carbon-fiber prepregs for dimensionally critical structures.

Graded Interface Models for more accurate Determination of van der Waals-London Dispersion Interactions across Grain Boundaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Benthem, Klaus; Tan, Guolong; French, Roger H

2006-01-01

Attractive van der Waals V London dispersion interactions between two half crystals arise from local physical property gradients within the interface layer separating the crystals. Hamaker coefficients and London dispersion energies were quantitatively determined for 5 and near- 13 grain boundaries in SrTiO3 by analysis of spatially resolved valence electron energy-loss spectroscopy (VEELS) data. From the experimental data, local complex dielectric functions were determined, from which optical properties can be locally analysed. Both local electronic structures and optical properties revealed gradients within the grain boundary cores of both investigated interfaces. The obtained results show that even in the presence ofmore » atomically structured grain boundary cores with widths of less than 1 nm, optical properties have to be represented with gradual changes across the grain boundary structures to quantitatively reproduce accurate van der Waals V London dispersion interactions. London dispersion energies of the order of 10% of the apparent interface energies of SrTiO3 were observed, demonstrating their significance in the grain boundary formation process. The application of different models to represent optical property gradients shows that long-range van der Waals V London dispersion interactions scale significantly with local, i.e atomic length scale property variations.« less

Plasma impact on structural, morphological and optical properties of copper acetylacetonate thin films

NASA Astrophysics Data System (ADS)

Abdel-Khalek, H.; El-Samahi, M. I.; El-Mahalawy, Ahmed M.

2018-06-01

The influence of plasma exposure on structural, morphological and optical properties of copper (II) acetylacetonate thin films deposited by thermal evaporation technique was investigated. Copper (II) acetylacetonate as-grown thin films were exposed to the atmospheric plasma for different times. The exposure of as-grown cu(acac)2 thin film to atmospheric plasma for 5 min modified its structural, morphological and optical properties. The effect of plasma exposure on structure and roughness of cu(acac)2 thin films was evaluated by XRD and AFM techniques, respectively. The XRD results showed an increment in crystallinity due to exposure for 5 min, but, when the exposure time reaches 10 min, the film was transformed to an amorphous state. The AFM results revealed a strong modification of films roughness when the average roughness decreased from 63.35 nm to 1 nm as a result of interaction with plasma. The optical properties of as-grown and plasma exposured cu(acac)2 thin films were studied using spectrophotometric method. The exposure of cu(acac)2 thin films to plasma produced the indirect energy gap decrease from 3.20 eV to 2.67 eV for 10 min exposure time. The dispersion parameters were evaluated in terms of single oscillator model for as-grown and plasma exposured thin films. The influence of plasma exposure on third order optical susceptibility was studied.

Synthesis, growth, structure, mechanical and optical properties of a new semi-organic 2-methyl imidazolium dihydrogen phosphate single crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagapandiselvi, P., E-mail: nagapandiselvip@ssn.edu.in; Baby, C.; Gopalakrishnan, R.

2016-09-15

Highlights: • 2MIDP crystals were grown by slow evaporation solution growth technique. • Single crystal XRD revealed self-assembled supramolecular framework. • Z scan technique is employed for third order nonlinear optical susceptibility. • Structure-property correlation is established. - Abstract: A new semi-organic compound, 2-methyl imidazolium dihydrogen phosphate (2MIDP), was prepared and good quality single crystals of 2MIDP were grown by slow evaporation solution growth technique. Crystal structure elucidated using Single crystal XRD showed that 2MIDP crystallizes in monoclinic system with P2{sub 1}/c space group. FT-IR, UV-Vis-NIR, Fluorescence and FT-NMR spectra confirm the molecular structure of 2MIDP. The UV-Vis-NIR spectra establishedmore » the suitability of the compound for NLO applications. TG-DSC showed that 2MIDP is thermally stable up to 200 °C. Mechanical characteristics like hardness number (H{sub v}), stiffness constant (C{sub 11}), yield strength (σ{sub v}), fracture toughness (K{sub c}) and brittleness index (B{sub i}) were assessed using Vicker’s microhardness tester. Third order nonlinear optical properties determined from Z-scan measurement using femto and picosecond lasers showed two photon reverse saturable absorption. The enhancement of nonlinear optical properties in femto second laser, revealed the suitability of 2MIDP for optical limiting applications.« less

Effects of site disorder, off-stoichiometry and epitaxial strain on the optical properties of magnetoelectric gallium ferrite.

PubMed

Roy, Amritendu; Mukherjee, Somdutta; Sarkar, Surajit; Auluck, Sushil; Prasad, Rajendra; Gupta, Rajeev; Garg, Ashish

2012-10-31

We present a combined experimental-theoretical study demonstrating the role of site disorder, off-stoichiometry and strain on the optical properties of magnetoelectric gallium ferrite. Optical properties (bandgap, refractive indices and dielectric constants) were experimentally obtained by performing ellipsometric studies over the energy range 0.8-4.2 eV on pulsed laser deposited epitaxial thin films of stoichiometric gallium ferrite with b-axis orientation and the data were compared with theoretical results. Calculations on the ground state structure show that the optical activity in GaFeO(3) arises primarily from O 2p-Fe 3d transitions. Further, inclusion of site disorder and epitaxial strain in the ground state structure significantly improves the agreement between the theory and the room temperature experimental data substantiating the presence of site disorder in the experimentally derived strained GaFeO(3) films at room temperature. We attribute the modification of the ground state optical behavior upon inclusion of site disorder to the corresponding changes in the electronic band structure, especially in Fe 3d states leading to a lowered bandgap of the material.

Structural, optical and enhanced power filtering application of PEG capped Zn1-xCoxS quantum dots

NASA Astrophysics Data System (ADS)

Vineeshkumar, T. V.; Prasanth, S.; Pragash, R.; Unnikrishnan, N. V.; Sudarsanakumar, C.

2018-04-01

Zn1-xCoxS (x= 0.05, 0.1, 0.15 and 0.2) quantum dots were synthesized successfully using co precipitation technique in polyethylene glycol (PEG) matrix. The PEG acted as a capping agent as well as a reducing agent. The structural and optical properties of the samples were studied by x-ray diffraction (XRD), TEM analysis and UV-Visible absorption. Nonlinear optical properties were measured using open aperture z-scan technique, employing frequency doubled (532 nm) pumping sources.

LASERS IN MEDICINE: Laser diagnostics of biofractals

NASA Astrophysics Data System (ADS)

Ushenko, A. G.

1999-12-01

An optical approach to the problem of modelling and diagnostics of the structures of biofractal formations was considered in relation to human bone tissue. A model was proposed for the optical properties of this tissue, including three levels of fractal organisation: microcrystalline, macrocrystalline, and architectural. The studies were based on laser coherent polarimetry ensuring the retrieval of the fullest information about the optical and polarisation properties of bone tissue. A method was developed for contactless noninvasive diagnostics of the orientational and mineralogical structure of bone tissue considered as a biofractal.

Structure-Dependent Optical Properties of Self-Organized Bi2Se3 Nanostructures: From Nanocrystals to Nanoflakes.

PubMed

Yang, Shang-Dong; Yang, Liao; Zheng, Yu-Xiang; Zhou, Wen-Jie; Gao, Meng-Yu; Wang, Song-You; Zhang, Rong-Jun; Chen, Liang-Yao

2017-08-30

Bismuth selenide (Bi 2 Se 3 ), with a wide bulk band gap and single massless Dirac cone at the surface, is a promising three-dimensional topological insulator. Bi 2 Se 3 possesses gapless surface states and an insulator-like bulk band gap as a new type of quantum matter. Different Bi 2 Se 3 nanostructures were prepared using electron beam evaporation with high production efficiency. Structural investigations by energy-dispersive X-ray analysis, scanning electron microscopy, and X-ray diffraction revealed the sample stoichiometries and the structural transition mechanism from nanocrystals to nanoflakes. The optical properties systematically probed and analyzed by spectroscopic ellipsometry showed strong dependence on the nanostructures and were also predicted to have structure-modifiable technological prospects. The optical parameters, plasma frequencies, scattering rates of the free electrons, and optical band gaps were related to the topological properties of the Bi 2 Se 3 nanostructures via light-matter interactions, offering new opportunities and approaches for studies on topological insulators and spintronics. The high-quality Bi 2 Se 3 nanostructures provide advantages in exploring novel physics and exploiting prospective applications.

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

NASA Astrophysics Data System (ADS)

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.

Properties of thin silver films with different thickness

NASA Astrophysics Data System (ADS)

Zhao, Pei; Su, Weitao; Wang, Reng; Xu, Xiaofeng; Zhang, Fengshan

2009-01-01

In order to investigate optical properties of silver films with different film thickness, multilayer composed of thin silver film sandwiched between ZnS films are sputtered on the float glass. The crystal structures, optical and electrical properties of films are characterized by various techniques, such as X-ray diffraction (XRD), spectrum analysis, etc. The optical constants of thin silver film are calculated by fitting the transmittance ( T) and reflectance ( R) spectrum of the multilayer. Electrical and optical properties of silver films thinner than 6.2 nm exhibit sharp change. However, variation becomes slow as film thickness is larger than 6.2 nm. The experimental results indicate that 6.2 nm is the optimum thickness for properties of silver.

Electronic and optical properties of Fe2SiO4 under pressure effect: ab initio study

NASA Astrophysics Data System (ADS)

Xiao, Lingping; Li, Xiaobin; Yang, Xue

2018-05-01

We report first-principles studies the structural, electronic, and optical properties of the Fe2SiO4 fayalite in orthorhombic structure, including pressure dependence of structural parameters, band structures, density of states, and optical constants up to 30 GPa. The calculated results indicate that the linear compressibility along b axis is significantly higher than a and c axes, which is in agreement with earlier work. Meanwhile, the pressure dependence of the electronic band structure, density of states and partial density of states of Fe2SiO4 fayalite up to 30 GPa were presented. Moreover, the evolution of the dielectric function, absorption coefficient (α(ω)), reflectivity (R(ω)), and the real part of the refractive index (n(ω)) at high pressure are also presented.

Magnetic, Optical and Magneto-optical Properties of Ni2MnGe Alloy Films

NASA Astrophysics Data System (ADS)

Kim, R. J.; Kudryavtsev, Y. V.; Kim, K. W.

2005-03-01

The influence of atomic ordering on the magnetic, the optical and the magneto-optical (MO) properties of Ni2MnGe Heusler alloy (HA) films was investigated. The bulk Ni2MnGe HA was prepared by arc melting, and the films were deposited by flash evaporation onto glass substrates at several substrate temperatures from 150 to 730 K. The bulk Ni2MnGe HA exhibits the cubic L21 structure with a = b = c = 0.5761 nm, and the annealed (at 573 K) bulk alloy is in the tetragonal structure with a = b = 0.5720 nm and c = 0.5865 nm. While the films deposited at 720 K show a well-ordered L21 structure, the deposition at 150 K < T < 710 K results in the formation of a nanocrystalline or an amorphous microstructure. It was found the structural disorder in Ni2MnGe films induces lack of the ferromagnetic order and noticeable changes in the optical and MO response.

Impact of low-pressure glow-discharge-pulsed plasma polymerization on properties of polyaniline thin films

NASA Astrophysics Data System (ADS)

Jatratkar, Aviraj A.; Yadav, Jyotiprakash B.; Deshmukh, R. R.; Barshilia, Harish C.; Puri, Vijaya; Puri, R. K.

2016-12-01

This study reports on polyaniline thin films deposited on a glass substrate using a low-pressure glow-discharge-pulsed plasma polymerization method. The polyaniline thin film obtained by pulsed plasma polymerization has been successfully demonstrated as an optical waveguide with a transmission loss of 3.93 dB cm-1, and has the potential to be employed in integrated optics. An attempt has been made to investigate the effect of plasma OFF-time on the structural, optical as well as surface properties of polyaniline thin film. The plasma ON-time has been kept constant and the plasma OFF-time has been varied throughout the work. The plasma OFF-time strongly influenced the properties of the polyaniline thin film, and a nanostructured and compact surface was revealed in the morphological studies. The plasma OFF-time was found to enhance film thickness, roughness, refractive index and optical transmission loss, whereas it reduced the optical band gap of the polyaniline thin films. Retention in the aromatic structure was confirmed by FTIR results. Optical studies revealed a π-π* electronic transition at about 317 nm as well as the formation of a branched structure. As compared with continuous wave plasma, pulsed plasma polymerization shows better properties. Pulsed plasma polymerization reduced the roughness of the film from 1.2 nm to 0.42 nm and the optical transmission loss from 6.56 dB cm-1 to 3.39 dB cm-1.

Nonlinear Optics with 2D Layered Materials.

PubMed

Autere, Anton; Jussila, Henri; Dai, Yunyun; Wang, Yadong; Lipsanen, Harri; Sun, Zhipei

2018-06-01

2D layered materials (2DLMs) are a subject of intense research for a wide variety of applications (e.g., electronics, photonics, and optoelectronics) due to their unique physical properties. Most recently, increasing research efforts on 2DLMs are projected toward the nonlinear optical properties of 2DLMs, which are not only fascinating from the fundamental science point of view but also intriguing for various potential applications. Here, the current state of the art in the field of nonlinear optics based on 2DLMs and their hybrid structures (e.g., mixed-dimensional heterostructures, plasmonic structures, and silicon/fiber integrated structures) is reviewed. Several potential perspectives and possible future research directions of these promising nanomaterials for nonlinear optics are also presented. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure, Electronic Properties, and Electrochemical Behavior of a Boron-Doped Diamond/Quartz Optically Transparent Electrode.

PubMed

Wächter, Naihara; Munson, Catherine; Jarošová, Romana; Berkun, Isil; Hogan, Timothy; Rocha-Filho, Romeu C; Swain, Greg M

2016-10-26

The morphology, microstructure, chemistry, electronic properties, and electrochemical behavior of a boron-doped nanocrystalline diamond (BDD) thin film grown on quartz were evaluated. Diamond optically transparent electrodes (OTEs) are useful for transmission spectroelectrochemical measurements, offering excellent stability during anodic and cathodic polarization and exposure to a variety of chemical environments. We report on the characterization of a BDD OTE by atomic force microscopy, optical spectroscopy, Raman spectroscopic mapping, alternating-current Hall effect measurements, X-ray photoelectron spectroscopy, and electrochemical methods. The results reported herein provide the first comprehensive study of the relationship between the physical and chemical structure and electronic properties of a diamond OTE and the electrode's electrochemical activity.

Structural, optical and dielectric properties of pure and chromium (Cr) doped nickel oxide nanoparticles

NASA Astrophysics Data System (ADS)

Gupta, Jhalak; Ahmed, Arham S.

2018-05-01

The pure and Cr doped nickel oxide (NiO) nanoparticles have been synthesized by cost effective co-precipitation method having nickel nitrate as initial precursor. The synthesized samples were characterized by X-Ray diffraction (XRD), UV-Visible Spectroscopy(UV-Vis) and LCR meter for structural, optical and dielectric properties respectively. The crystallite size of pure nickel oxide nanoparticles characterized by XRD using Debye Scherer's formula was found to be 21.7nm and the same decreases on increasing Cr concentration whereas optical and dielectric properties were analyzed by UV-Vis and LCR meter respectively. The energy band gaps were determined by UV-Vis using Tauc relation.

Structures and Optical Properties of Hydrazones Derived from Biological Polyenes

NASA Astrophysics Data System (ADS)

Nakashima, Takayasu; Yamada, Takashi; Hashimoto, Hideki; Kobayashi, Takayoshi

2001-08-01

A set of hydrazone molecules was derived from a series of biological polyenes that have different polyene chain-lengths with common substituent group of 2,4-dinitrophenylhydrazine. Their structures were determined by high-resolution NMR spectroscopy as well as X-ray crystallography, and their optical properties were investigated by room and low temperature optical absorption spectroscopy. Among the derivatives so far synthesized, the one that has the shortest polyene chain (C13-DNPH) afforded single crystals without inversion symmetry, hence applicable for the second-order nonlinear optical devices. Molecular structures in the crystals were closely inspected in order to explain the cause to violate the inversion symmetry. Hydrazones derived in this study gave rise to two transition moments along the molecular axis. Comparison of the optical absorption spectra among the derivatives showed a unique phenomenon that could be attributed to the crossover of the excited state potential energy surfaces along the elongation of the polyene chain-lengths.

Structures and Optical Properties of Hydrazones Derived from Biological Polyenes

NASA Astrophysics Data System (ADS)

Nakashima, Takayasu; Yamada, Takashi; Hashimoto, Hideki; Kobayashi, Takayoshi

A set of hydrazone molecules was derived from a series of biological polyenes that have different polyene chain-lengths with common substituent group of 2,4-dinitrophenylhydrazine. Their structures were determined by high-resolution NMR spectroscopy as well as X-ray crystallography, and their optical properties were investigated by room and low temperature optical absorption spectroscopy. Among the derivatives so far synthesized, the one that has the shortest polyene chain (C13-DNPH) afforded single crystals without inversion symmetry, hence applicable for the second-order nonlinear optical devices. Molecular structures in the crystals were closely inspected in order to explain the cause to violate the inversion symmetry. Hydrazones derived in this study gave rise to two transition moments along the molecular axis. Comparison of the optical absorption spectra among the derivatives showed a unique phenomenon that could be attributed to the crossover of the excited state potential energy surfaces along the elongation of the polyene chain-lengths.

Structural, stability, and vibrational properties of BinPm clusters

NASA Astrophysics Data System (ADS)

Shen, Wanting; Han, Lihong; Liang, Dan; Zhang, Chunfang; Ruge, Quhe; Wang, Shumin; Lu, Pengfei

2018-04-01

An in-depth investigation is performed on stability mechanisms, electronic and optical properties of III-V semiconductor vapor phases clusters. First principles electronic structure calculations of CAM-B3LYP are performed on neutral BinPm (n + m ≤ 14) clusters. The geometrical evolution of all stable structures remains amorphous as the clusters size increases. Binding energies (BEs), energy gains and highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) gaps confirm that all four-atom structures of BinPm clusters have more stable optical properties. Orbitals composition and vibrational spectra of stable clusters are analyzed. Our calculations will contribute to the study of diluted bismuth alloys and compounds.

Experimental investigation on light propagation through apple tissue structures

NASA Astrophysics Data System (ADS)

Askoura, Mohamed Lamine; Piron, Vianney; Vaudelle, Fabrice; L'Huillier, Jean-Pierre; Madieta, Emmanuel; Mehinagic, Emira

2015-07-01

The interaction of light with biological materials, such as fruits and vegetables, is a complex process which involves both absorption, and scattering events at different scales. Measuring the optical properties of a fruit allows understanding the physical and chemical characteristics. In this paper, an optical bench based on the use of a continuous laser source and a CCD camera was developed to study the light diffusion inside apple tissue structures. The method refers to the well-known steady-state spatially resolved method. First, the optoelectronics system was tested with a tissue phantom in order to show the optimal sensing range required to obtain the best estimated optical properties. Second, experimental results were obtained using peeled and unpeeled apples as interrogated tissues. The data were confronted with a diffusion model in order to extract the optical properties at two wavelengths of 633, and 852 nm. To better understand the effect of the apple tissue structures, investigations into the propagation of light through a half cut apple were also performed.

Impact of nucleation of carbonaceous clusters on structural, electrical and optical properties of Cr+-implanted PMMA

NASA Astrophysics Data System (ADS)

Arif, Shafaq; Rafique, M. Shahid; Saleemi, Farhat; Naab, Fabian; Toader, Ovidiu; Mahmood, Arshad; Aziz, Uzma

2016-09-01

Specimens of polymethylmethacrylate (PMMA) have been implanted with 400 keV Cr+ ions at different ion fluences ranging from 5 × 1013 to 5 × 1015 ions/cm2. The possible chemical reactions involved in the nucleation of conjugated carbonaceous clusters in implanted PMMA are discussed. Furthermore, impact of formation of carbonaceous clusters on structural, optical, electrical and morphological properties of implanted PMMA has been examined. The structural modifications in implanted PMMA are observed by Raman spectroscopy. The variation in optical band gap and Urbach energy is measured using UV-visible spectroscopic analysis. The effects of Cr+ ion implantation on electrical and morphological properties are investigated by four-probe apparatus and atomic force microscopy, respectively. The Raman spectroscopic analysis confirmed the formation of carbonaceous clusters with the transformation of implanted layer of PMMA into amorphous carbon. Simultaneously, the optical band gap of implanted PMMA has reduced from 3.13 to 0.85 eV. The increase in Urbach energy favors the decline in band gap together with the structural modification in implanted PMMA. As a result of Cr+ ion implantation, the electrical conductivity of PMMA has improved from 2.14 ± 0.06 × 10-10 S/cm (pristine) to 7.20 ± 0.36 × 10-6 S/cm. The AFM images revealed a decrease in surface roughness with an increment in ion fluence up to 5 × 1014 ions/cm2. The modification in the electrical, optical and structural properties makes the PMMA a promising candidate for its future utilization, as a semiconducting and optically active material, in various fields like plastic electronics and optoelectronic devices.

The properties and applications of nanodiamonds.

PubMed

Mochalin, Vadym N; Shenderova, Olga; Ho, Dean; Gogotsi, Yury

2011-12-18

Nanodiamonds have excellent mechanical and optical properties, high surface areas and tunable surface structures. They are also non-toxic, which makes them well suited to biomedical applications. Here we review the synthesis, structure, properties, surface chemistry and phase transformations of individual nanodiamonds and clusters of nanodiamonds. In particular we discuss the rational control of the mechanical, chemical, electronic and optical properties of nanodiamonds through surface doping, interior doping and the introduction of functional groups. These little gems have a wide range of potential applications in tribology, drug delivery, bioimaging and tissue engineering, and also as protein mimics and a filler material for nanocomposites.

Systematic investigation of structural, electronic, optical and thermal properties of ternary MoAlB; an ab initio approach

NASA Astrophysics Data System (ADS)

Rajpoot, Priyanka; Rastogi, Anugya; Verma, U. P.

2018-02-01

Structural, electronic, optical and thermal properties of molybdenum aluminum boride (MoAlB) have been analyzed systematically using the full potential linearized augmented plane wave method based on density functional theory at ambient condition as well as high pressure and high temperature. Density of states and band structure calculation reflect the metallic character of MoAlB. In addition to this, the electron charge density calculation reveals the strong covalent bonding, in between ‘B’ atoms as well as ‘Mo’ and ‘B’ atoms. Optical parameters exhibit anisotropic nature and MoAlB become transparent in ultraviolet region for the radiation of energy above 25 eV. The thermal properties were investigated by using the quasi-harmonic Debye model at high temperature and high pressure.

Influence of Ca2+ doped on structural and optical properties of RPO4 (R = Ce3+, Nd3+ and Pr3+) compounds

NASA Astrophysics Data System (ADS)

Lemdek, El Mokhtar; Benkhouja, Khalil; Touhtouh, Samira; Sbiaai, Khalid; Arbaoui, Abdezzahid; Bakasse, Mina; Hajjaji, Abdelowahed; Boughaleb, Yahia; Saez-Puche, Regino

2013-11-01

This paper investigates the effect of doping by Ca2+ ions on the structural and optical properties of RPO4 (R = Ce3+, Nd3+ and Pr3+) compounds. A simple ceramic method in air at 900 °C was used to prepare all compounds. The structural characterization of compounds was carried out by using X-ray powder diffraction (XRD) and IR spectroscopy. Optical properties were characterized by reflectance spectral data and by colorimeter. The results reveal a single monazite phase for x values up to 0.4. The lattice parameters of the synthesized samples decrease linearly with the reduction of ionic radius of the Ce3+. These rare earth phosphates based materials have a potential to be adopted for the eco-friendly colorants for paints and plastics.

Influence of bias voltage on structural and optical properties of TiN{sub x} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Omveer, E-mail: poonia.omveer@gmail.com; Dahiya, Raj P.; Deenbandhu Chhotu Ram University of Science and Technology, Murthal – 131039

In the present work, Ti thin films were deposited on Si substrate using DC sputtering technique. Indigenous hot cathode arc discharge plasma system was used for nitriding over these samples, where the plasma parameters and work piece can be controlled independently. A mixture of H{sub 2} and N{sub 2} gases (in the ratio of 80:20) was supplied into the plasma chamber. The effect of bias voltage on the crystal structure, morphology and optical properties was investigated by employing various physical techniques such as X-ray Diffraction, Atomic Force Microscopy and UV-Vis spectrometry. It was found that bias voltage affects largely themore » crystal structure and band gap which in turn is responsible for the modifications in optical properties of the deposited films.« less

Screened Hybrid and DFT + U Studies of the Structural, Electronic, and Optical Properties of U3O8

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wen, Xiaodong; Martin, Richard L.; Scuseria, Gustavo E.

2012-11-26

A systematic comparison of the structures and electronic and optical properties of U3O8 in the c2mm, P¯62m, and P21/m structures (the α, β, and γ phases, respectively) is performed using density functional theory + U (PBE + U) and the Heyd–Scuseria–Ernzerhof screened hybrid functional (HSE). The relationship between the semiconducting C2mm phase of U3O8 and the high temperature, metallic P¯62m phase is explored in more detail. Our calculated results show that the HSE functional gives a better description of the electronic and optical properties when compared with available experimental data for the α and β phases, but neither approach doesmore » particularly well for the high pressure γ phase.« less

First-principles calculations of structural, elastic, electronic, and optical properties of perovskite-type KMgH3 crystals: novel hydrogen storage material.

PubMed

Reshak, Ali H; Shalaginov, Mikhail Y; Saeed, Yasir; Kityk, I V; Auluck, S

2011-03-31

We report a first-principles study of structural and phase stability in three different structures of perovskite-types KMgH(3) according to H position. While electronic and optical properties were measured only for stable perovskite-type KMgH(3), our calculated structural parameters are found in good agreement with experiment and other theoretical results. We also study the electronic charge density space distribution contours in the (200), (101), and (100) crystallographic planes, which gives better insight picture of chemical bonding between K-H, K-Mg-H, and Mg-H. Moreover, we have calculated the electronic band structure dispersion, total, and partial density of electron states to study the band gap origin and the contribution of s-band of H, s and p-band of Mg in the valence band, and d-band of K in the conduction band. Furthermore, optical features such as dielectric functions, refractive indices, extinction coefficient, optical reflectivity, absorption coefficients, optical conductivities, and loss functions of stable KMgH(3) were calculated for photon energies up to 40 eV.

Electronic and optical properties of the LiCdX (X = N, P, As and Sb) filled-tetrahedral compounds with the Tran–Blaha modified Becke–Johnson density functional

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bouhemadou, A., E-mail: a_bouhemadou@yahoo.fr; Bin-Omran, S.; Department of Physics, Faculty of Science & Humanitarian Studies, Salman Bin Abdalaziz University, Alkharj 11942

Highlights: • Electronic and optical properties of the LiCdX compounds have been predicted. • Tran–Blaha-modified Becke–Johnson functional significantly improves the band gap. • We predict a direct band gap in all of the considered LiCdX compounds. • Origin of the peaks in the optical spectra is determined. - Abstract: The structural, electronic and optical properties of the LiCdN, LiCdP, LiCdAs and LiCdSb filled-tetrahedral compounds have been explored from first-principles. The calculated structural parameters are consistent with the available experimental results. Since DFT with the common LDA and GGA underestimates the band gap, we use a new developed functional able tomore » accurately describe the electronic structure of semiconductors, namely the Tran–Blaha-modified Becke–Johnson potential. The four investigated compounds demonstrate semiconducting behavior with direct band gap ranging from about 0.32 to 1.65 eV. The charge-carrier effective masses are evaluated at the topmost valence band and at the bottommost conduction band. The evolution of the value and nature of the energy band gap under pressure effect is also investigated. The frequency-dependent complex dielectric function and some macroscopic optical constants are estimated. The microscopic origins of the structures in the optical spectra are determined in terms of the calculated energy band structures.« less

Theoretical study on the electronic and optical properties of bulk and surface (001) InxGa1-xAs

NASA Astrophysics Data System (ADS)

Liu, XueFei; Ding, Zhao; Luo, ZiJiang; Zhou, Xun; Wei, JieMin; Wang, Yi; Guo, Xiang; Lang, QiZhi

2018-05-01

The optical properties of surface and bulk InxGa1-xAs materials are compared systematically first time in this paper. The band structures, density of states and optical properties including dielectric function, reflectivity, absorption coefficient, loss function and refractive index of bulk and surface InxGa1-xAs materials are investigated by first-principles based on plane-wave pseudo-potentials method within the LDA approximation. The results agree well with the available theoretical and experimental studies and indicate that the electronic and optical properties of bulk and surface InxGa1-xAs materials are much different, and the results show that the considered optical properties of the both materials vary with increasing indium composition in an opposite way. The calculations show that the optical properties of surface In0.75Ga0.25As material are unexpected to be far from the other two indium compositions of surface InxGa1-xAs materials while the optical properties of bulk InxGa1-xAs materials vary with increasing indium composition in an expected regular way.

Optical and structural properties of colloidal zirconia nanoparticles prepared by arc discharge in liquid

NASA Astrophysics Data System (ADS)

Peymani forooshani, Reza; Poursalehi, Reza; Yourdkhani, Amin

2018-01-01

Zirconia is one of the important ceramic materials with unique properties such as high melting point, high ionic conductivity, high mechanical properties and low thermal conductivity. Therefore, zirconia is one of the useful materials in refractories, thermal barriers, cutting tools, oxygen sensors electrolytes, catalysis, catalyst supports and solid oxide fuel cells. Recently, direct current (DC) arc discharge is extensively employed to synthesis of metal oxide nanostructures in liquid environments. The aim of this work is the synthesis of colloidal zirconia nanoparticles by DC arc discharge method in water as a medium. Arc discharge was ignited between two pure zirconium electrodes in water. Optical and structural properties of prepared colloidal nanoparticles were investigated. Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and UV-visible spectroscopy, were employed for characterization of particle size, morphology, crystal structure and optical properties, respectively. SEM images demonstrate that the nanoparticles are spherical in shape with an average size lower than 38 nm. The XRD patterns of the nanoparticles were consistent with tetragonal and monoclinic zirconia crystal structures. The optical transmission spectra of the colloidal solution show optical characteristic of zirconia nanoparticles as a wide band gap semiconductor with no absorption peak in visible wavelength with the considerable amount of oxygen deficiency. Oxidation of colloidal nanoparticles in water could be explained via reaction with either dissociated oxygen from water in hot plasma region or with dissolved oxygen in water. The results provide a simple and flexible method for preparation of zirconia nanoparticles with a capability of mass production without environmental footprints.

Effects of silver impurity on the structural, electrical, and optical properties of ZnO nanowires

PubMed Central

2011-01-01

1, 3, and 5 wt.% silver-doped ZnO (SZO) nanowires (NWs) are grown by hot-walled pulsed laser deposition. After silver-doping process, SZO NWs show some change behaviors, including structural, electrical, and optical properties. In case of structural property, the primary growth plane of SZO NWs is switched from (002) to (103) plane, and the electrical properties of SZO NWs are variously measured to be about 4.26 × 106, 1.34 × 106, and 3.04 × 105 Ω for 1, 3, and 5 SZO NWs, respectively. In other words, the electrical properties of SZO NWs depend on different Ag ratios resulting in controlling the carrier concentration. Finally, the optical properties of SZO NWs are investigated to confirm p-type semiconductor by observing the exciton bound to a neutral acceptor (A0X). Also, Ag presence in ZnO NWs is directly detected by both X-ray photoelectron spectroscopy and energy dispersive spectroscopy. These results imply that Ag doping facilitates the possibility of changing the properties in ZnO NWs by the atomic substitution of Ag with Zn in the lattice. PMID:21985620

First-principle calculations of crystal structures, electronic structures, and optical properties of RETaO4 (RE = Y, La, Sm, Eu, Dy, Er)

NASA Astrophysics Data System (ADS)

Ma, Zhuang; Zheng, Jiayi; Wang, Song; Gao, Lihong

2018-01-01

It is an effective method to protect components from high power laser damage using high reflective materials. The rare earth tantalates RETaO4 with high dielectric constant suggests that they may have very high reflectivity, according to the relationship between dielectric constant and reflectivity. The crystal structures, electronic structures, and optical properties of RETaO4 (RE=Y, La, Sm, Eu, Dy, Er) have been studied by first-principle calculations. With the increasing atomic number of RE (i.e., the number of 4f electrons), a 4f electron shell moves from the bottom of conduction band to the forbidden gap and then to the valence band. The relationship between the electronic structures and optical properties is explored. The electron transitions among O 2p states, RE 4f states, and Ta 5d states have a key effect on optical properties such as dielectric function, absorption coefficient, and reflectivity. For the series of RETaO4, the appearance of the 4f electronic states will obviously promote the improvement of reflectivity. When the 4f states appear at the middle of the forbidden gap, the reflectivity reaches the maximum. The reflectivity of EuTaO4 at 1064 nm is up to 93.47%, indicating that it has potential applications in the antilaser radiation area.

Theoretical and experimental investigations of optical, structural and electronic properties of the lower-dimensional hybrid [NH3-(CH2)10-NH3]ZnCl4

NASA Astrophysics Data System (ADS)

El Mrabet, R.; Kassou, S.; Tahiri, O.; Belaaraj, A.; Guionneau, P.

2016-10-01

In the current study, a combination between theoretical and experimental studies has been made for the hybrid perovskite [NH3-(CH2)10-NH3]ZnCl4. The density functional theory (DFT) was performed to investigate structural and electronic properties of the tilted compound. A local approximation (LDA) and semi-local approach (GGA) were employed. The results are obtained using, respectively, the local exchange correlation functional of Perdew-Wang 92 (PW92) and semi local functional of Perdew-Burke-Ernzerhof (PBE). The optimized cell parameters are in good agreement with the experimental results. Electronic properties have been studied through the calculation of band structures and density of state (DOS), while structural properties are investigated by geometry optimization of the cell. Fritz-Haber-Institute (FHI) pseudopotentials were employed to perform all calculations. The optical diffuse reflectance spectra was mesured and applied to deduce the refractive index ( n), the extinction coefficient ( k), the absorption coefficient (α), the real and imaginary dielectric permittivity parts (ɛr,ɛi)) and the optical band gap energy Eg. The optical band gap energy value shows good consistent with that obtained from DFT calculations and reveals the insulating behavior of the material.

Structural, optoelectronic, and thermoelectric properties of AZn13 (A=Na, K, Ca, Sr, Ba) compounds

NASA Astrophysics Data System (ADS)

Basit, Abdul; Murtaza, G.; Mahmood, Asif; Yar, Abdullah; Muhammad, S.

2016-08-01

We report the structural, electronic, optical, and thermoelectric properties of the five cubic alkali-earth transition-metals AZn13 (A-Na, K, Ca, Sr, Ba) using density functional theory. Structural properties, electronic structures and optical behaviors are calculated explicitly via highly accurate contemporary full potential-linearized augmented plane wave (FP-LAPW) method. The investigated ground state data of these materials is quite close to the experimental information. The modified Becke-Johnson (mBJ) predicts the intermetallic nature of AZn13 (A-Na, K, Ca, Sr, Ba) materials. The complex dielectric function of these intermetallic compounds has been calculated and the observed noticeable peaks are examined through mBJ. With the help of complex dielectric function, the other important optical parameters like reflectivities, conductivities and refractive indices of AZn13 (A-Na, K, Ca, Sr, Ba) have been calculated as a function of energy. The optical response suggests that AZn13 (A-Na, K, Ca, Sr, Ba) compounds can be used for the optoelectronic devices. Further, the thermoelectric properties have been calculated through BoltzTraP program, the calculated values for different thermoelectric parameters recommend that these AZn13 (A-Na, K, Ca, Sr, Ba) materials are the suitable candidates for thermoelectric applications.

Directed-Assembly of Block Copolymers for Large-Scale, Three-Dimensional, Optical Metamaterials at Visible Wavelengths. Final LDRD Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hiszpanski, Anna M.

Metamaterials are composites with patterned subwavelength features where the choice of materials and subwavelength structuring bestows upon the metamaterials unique optical properties not found in nature, thereby enabling optical applications previously considered impossible. However, because the structure of optical metamaterials must be subwavelength, metamaterials operating at visible wavelengths require features on the order of 100 nm or smaller, and such resolution typically requires top-down lithographic fabrication techniques that are not easily scaled to device-relevant areas that are square centimeters in size. In this project, we developed a new fabrication route using block copolymers to make over large device-relevant areas opticalmore » metamaterials that operate at visible wavelengths. Our structures are smaller in size (sub-100 nm) and cover a larger area (cm 2) than what has been achieved with traditional nanofabrication routes. To guide our experimental efforts, we developed an algorithm to calculate the expected optical properties (specifically the index of refraction) of such metamaterials that predicts that we can achieve surprisingly large changes in optical properties with small changes in metamaterials’ structure. In the course of our work, we also found that the ordered metal nanowires meshes produced by our scalable fabrication route for making optical metamaterials may also possibly act as transparent electrodes, which are needed in electrical displays and solar cells. We explored the ordered metal nanowires meshes’ utility for this application and developed design guidelines to aide our experimental efforts.« less

Analysis of dependent scattering mechanism in hard-sphere Yukawa random media

NASA Astrophysics Data System (ADS)

Wang, B. X.; Zhao, C. Y.

2018-06-01

The structural correlations in the microscopic structures of random media can induce the dependent scattering mechanism and thus influence the optical scattering properties. Based on our recent theory on the dependent scattering mechanism in random media composed of discrete dipolar scatterers [B. X. Wang and C. Y. Zhao, Phys. Rev. A 97, 023836 (2018)], in this paper, we study the hard-sphere Yukawa random media, in order to further elucidate the role of structural correlations in the dependent scattering mechanism and hence optical scattering properties. Here, we consider charged colloidal suspensions, whose effective pair interaction between colloids is described by a screened Coulomb (Yukawa) potential. By means of adding salt ions, the pair interaction between the charged particles can be flexibly tailored and therefore the structural correlations are modified. It is shown that this strategy can affect the optical properties significantly. For colloidal TiO2 suspensions, the modification of electric and magnetic dipole excitations induced by the structural correlations can substantially influence the optical scattering properties, in addition to the far-field interference effect described by the structure factor. However, this modification is only slightly altered by different salt concentrations and is mainly because of the packing-density-dependent screening effect. On the other hand, for low refractive index colloidal polystyrene suspensions, the dependent scattering mechanism mainly involves the far-field interference effect, and the effective exciting field amplitude for the electric dipole almost remains unchanged under different structural correlations. The present study has profound implications for understanding the role of structural correlations in the dependent scattering mechanism.

Influence of the aggregate state on band structure and optical properties of C60 computed with different methods

NASA Astrophysics Data System (ADS)

Pal, Amrita; Arabnejad, Saeid; Yamashita, Koichi; Manzhos, Sergei

2018-05-01

C60 and C60 based molecules are efficient acceptors and electron transport layers for planar perovskite solar cells. While properties of these molecules are well studied by ab initio methods, those of solid C60, specifically its optical absorption properties, are not. We present a combined density functional theory-Density Functional Tight Binding (DFTB) study of the effect of solid state packing on the band structure and optical absorption of C60. The valence and conduction band edge energies of solid C60 differ on the order of 0.1 eV from single molecule frontier orbital energies. We show that calculations of optical properties using linear response time dependent-DFT(B) or the imaginary part of the dielectric constant (dipole approximation) can result in unrealistically large redshifts in the presence of intermolecular interactions compared to available experimental data. We show that optical spectra computed from the frequency-dependent real polarizability can better reproduce the effect of C60 aggregation on optical absorption, specifically with a generalized gradient approximation functional, and may be more suited to study effects of molecular aggregation.

Role of Mn2+ concentration in the linear and nonlinear optical properties of Ni1-xMnxSe nanoparticles

NASA Astrophysics Data System (ADS)

Anugop, B.; Prasanth, S.; Rithesh Raj, D.; Vineeshkumar, T. V.; Pranitha, S.; Mahadevan Pillai, V. P.; Sudarsanakumar, C.

2016-12-01

Ni1-xMnxSe nanoparticles (x = 0.1, 0.3, 0.5, 0.7, 0.9) were successfully synthesized by chemical co-precipitation method and their structural and optical properties were studied using X-ray diffraction, transmission electron microscopy, UV-Visible absorption and photo luminescence spectroscopy. XRD pattern reveals the hexagonal structure of the particles and the peak positions were shifted to higher 2θ values with increase in Mn2+ concentration. The average particle size determined from XRD varies from 6 to 11 nm. The UV-Visible absorption spectrum shows absorption edge around the blue region and is red-shifted with increasing Mn2+ concentration consequently the optical bandgap energy is decreasing. The PL emission spectrum shows a broad emission around 380 nm, and the intensity of the emission decreases with increase in Mn2+ concentration. The nonlinear optical properties of the samples were analysed using Z-scan technique and the samples show optical limiting behaviour and the 2 PA coefficient increases with increasing Mn2+ concentration. Overall, manganese concentration influences the linear and nonlinear optical properties of Ni1-xMnxSe nanoparticles.

Influence Al doped ZnO nanostructure on structural and optical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramelan, Ari Handono, E-mail: aramelan@mipa.uns.ac.id; Wahyuningsih, Sayekti; Chasanah, Uswatul

2016-04-19

The preparation of Al-doped ZnO (AZO) thin films prepared by the spin-coating method was reported. Preparation of AZO was conducted by annealing treatment at a temperature of 700°C. While the spin-coating process of AZO thin films were done at 2000 and 3000 rpm respectively. The structural properties of ZnO were determined by X- ray diffraction (XRD) analysis. ZnOnanostructure was formed after annealed at atemperature of 400°C.The morphology of ZnO was determined by Scanning Electron Microscopy (SEM) showed the irregular morphology about 30-50µm in size. Al doped on ZnO influenced the optical properties of those material. Increasing Al contain on ZnO causemore » of shifting to the lower wavelength. The optical properties of the ZnO as well as AZO films showed that higher reflectance on the ultraviolet region so those materials were used as anti-reflecting agent.Al addition significantly enhance the optical transparency and induce the blue-shift in optical bandgap of ZnO films.« less

Electronic and optical properties of GaN under pressure: DFT calculations

NASA Astrophysics Data System (ADS)

Javaheri, Sahar; Boochani, Arash; Babaeipour, Manuchehr; Naderi, Sirvan

2017-12-01

Optical and electronic properties of ZB, RS and WZ structures of gallium nitride (GaN) are studied in equilibrium and under pressure using the first-principles calculation in the density functional theory (DFT) framework to obtain quantities like dielectric function, loss function, reflectance and absorption spectra, refractive index and their relation parameters. The electronic properties are studied using EV-GGA and GGA approximations and the results calculated by EV-GGA approximation were found to be much closer to the experimental results. The interband electron transitions are studied using the band structure and electron transition peaks in the imaginary part of the dielectric function; these transitions occur in three structures from N-2p orbital to Ga-4s and Ga-4p orbitals in the conduction band. Different optical properties of WZ structure were calculated in two polarization directions of (100) and (001) and the results were close to each other. Plasmon energy corresponding to the main peak of the energy-loss function in RS with the value of 26 eV was the highest one, which increased under pressure. In general, RS shows more different properties than WZ and ZB.

Thermodynamical study of boron doped CeX{sub 3} (X=Pd, Rh)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Ramesh; Dwivedi, Shalini; Sharma, Yamini, E-mail: sharma.yamini62@gmail.com

2016-05-06

The structural, electronic, thermal, and optical properties of cubic non magnetic CeX{sub 3}(X=Pd, Rh) compounds which crystallize in the Au{sub 3}Cu structure have been studied using the projected augmented wave (PAW) method within the density functional theory (DFT) with generalized gradient approximation (GGA) for exchange correlation potential. In this paper we have calculated the band structure which are interpreted using the density of states. The optical properties such as extinction coefficients clearly illustrate the changes in CeX{sub 3} due to intercalation of boron. Lattice instability is observed in CePd{sub 3}B from the calculated dynamical properties.

Structural, electronic, and optical properties of the C-C complex in bulk silicon from first principles

NASA Astrophysics Data System (ADS)

Timerkaeva, Dilyara; Attaccalite, Claudio; Brenet, Gilles; Caliste, Damien; Pochet, Pascal

2018-04-01

The structure of the CiCs complex in silicon has long been the subject of debate. Numerous theoretical and experimental studies have attempted to shed light on the properties of these defects that are at the origin of the light emitting G-center. These defects are relevant for applications in lasing, and it would be advantageous to control their formation and concentration in bulk silicon. It is therefore essential to understand their structural and electronic properties. In this paper, we present the structural, electronic, and optical properties of four possible configurations of the CiCs complex in bulk silicon, namely, the A-, B-, C-, and D-forms. The configurations were studied by density functional theory and many-body perturbation theory. Our results suggest that the C-form was misinterpreted as a B-form in some experiments. Our optical investigation also tends to exclude any contribution of A- and B-forms to light emission. Taken together, our results suggest that the C-form could play an important role in heavily carbon-doped silicon.

Interaction of light with hematite hierarchical structures: Experiments and simulations

NASA Astrophysics Data System (ADS)

Distaso, Monica; Zhuromskyy, Oleksander; Seemann, Benjamin; Pflug, Lukas; Mačković, Mirza; Encina, Ezequiel; Taylor, Robin Klupp; Müller, Rolf; Leugering, Günter; Spiecker, Erdmann; Peschel, Ulf; Peukert, Wolfgang

2017-03-01

Mesocrystalline particles have been recognized as a class of multifunctional materials with potential applications in different fields. However, the internal organization of nanocomposite mesocrystals and its influence on the final properties have not yet been investigated. In this paper, a novel strategy based on electrodynamic simulations is developed to shed light on how the internal structure of mesocrystals influences their optical properties. In a first instance, a unified design protocol is reported for the fabrication of hematite/PVP particles with different morphologies such as pseudo-cubes, rods-like and apple-like structures and controlled particle size distributions. The optical properties of hematite/PVP mesocrystals are effectively simulated by taking their aggregate and nanocomposite structure into consideration. The superposition T-Matrix approach accounts for the aggregate nature of mesocrystalline particles and validate the effective medium approximation used in the framework of the Mie theory and electromagnetic simulation such as Finite Element Method. The approach described in our paper provides the framework to understand and predict the optical properties of mesocrystals and more general, of hierarchical nanostructured particles.

Optical and electronic properties of SO2 molecule adsorbed on Si-doped (8, 0) boron nitride nanotube

NASA Astrophysics Data System (ADS)

Guo, Shuang-Shuang; Wei, Xiu-Mei; Zhang, Jian-Min; Zhu, Gang-Qiang; Guo, Wan-Jin

2016-09-01

The study of the optical properties of pristine BNNT, Si-doped BNNTs and SO2 molecule adsorption on Si-doped BNNTs is that, to our knowledge, few relevant research have ever been found. In this paper, the adsorption behaviors of Sulfur dioxide (SO2) molecule on Si-doped Boron nitride nanotubes (BNNTs) are investigated applying the first-principles calculations. The main contribution of this paper is that the foremost investigation for the optical properties of the pristine BNNT, Si-doped BNNTs and SO2 adsorption on Si-doped BNNTs. Additionally, the electronic properties and the structural properties are also presented. In our calculations of optical properties, the dielectric constant, the refractive index and the absorption coefficient are obtained. Comparing the pristine BNNT, our results indicate that, the blue-shifts (in the main peaks of the dielectric constant of SiB -BNNT and SO2-SiB -BNNT), and the red-shifts (in the main peaks of the refractive index of SiN -BNNT and SO2-SiN -BNNT) are appeared. Under these conditions, Si-doped BNNT and Si-doped BNNT with SO2 adsorption, the gaps are reduced both for the speculated optical band gaps and the electronic structure band gaps.

The under-pressure behaviour of mechanical, electronic and optical properties of calcium titanate and its ground state thermoelectric response

NASA Astrophysics Data System (ADS)

Noor, N. A.; Alay-e-Abbas, S. M.; Hassan, M.; Mahmood, I.; Alahmed, Z. A.; Reshak, A. H.

2017-08-01

In this study, the elastic, electronic, optical and thermoelectric properties of CaTiO3 perovskite oxide have been investigated using first-principles calculations. The generalised gradient approximation (GGA) has been employed for evaluating structural and elastic properties, while the modified Becke Johnson functional is used for studying the optical response of this compound. In addition to ground state physical properties, we also investigate the effects of pressure (0, 30, 60, 90 and 120 GPa) on the electronic structure of CaTiO3. The application of pressure from 0 to 90 GPa shows that the indirect band gap (Γ-M) of CaTiO3 increases with increasing pressure and at 120 GPa it spontaneously decreases transforming cubic CaTiO3 to a direct (Γ-Γ) band gap material. The complex dielectric function and some optical parameters are also investigated under the application of pressures. All the calculated optical properties have been found to exhibit a shift to the higher energies with the increase of applied pressure suggesting potential optoelectronic device applications of CaTiO3. The thermoelectric properties of CaTiO3 have been computed at 0 GPa in terms of electrical conductivity, thermal conductivity and Seebeck coefficient.

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

PubMed

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.

Structural and optical properties of ITO and Cu doped ITO thin films

NASA Astrophysics Data System (ADS)

Chakraborty, Deepannita; Kaleemulla, S.; Rao, N. Madhusudhana; Subbaravamma, K.; Rao, G. Venugopal

2018-04-01

(In0.95Sn0.05)2O3 and (In0.90Cu0.05Sn0.05)2O3 thin films were coated onto glass substrate by electron beam evaporation technique. The structural and optical properties of ITO and Cu doped ITO thin films have been studied by X-ray diffractometer (XRD) and UV-Vis-NIR spectrophotometer. The crystallite size obtained for ITO and Cu doped ITO thin films was in the range of 24 nm to 22 nm. The optical band gap of 4 eV for ITO thin film sample has been observed. The optical band gap decreases to 3.85 eV by doping Cu in ITO.

High Fidelity Additive Manufacturing of Optically Transparent Glass Structures

NASA Astrophysics Data System (ADS)

Inamura, Chikara

Glass has been an integral part of human civilization with expressions across scales and disciplines: from the microscope to the telescope, from fiber optics to mobile interface, and from the petri dish to a building envelope. Such a diverse range of applications is enabled by the inherent material properties including mechanical strength, optical transparency and chemical inertness. Additive manufacturing provides opportunities for integrating the unique properties of glass to engineer novel structures that are functionary graded through precise spatiotemporal deposition of molten glass. This talk presents the Mediated Matter Group's latest development of a novel additive manufacturing platform, and related processes, for 3D Printing optically transparent glass for architectural scale applications.

Hybrid Perovskite Phase Transition and Its Ionic, Electrical and Optical Properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoque, Md Nadim Ferdous; Islam, Nazifah; Zhu, Kai

Hybrid perovskite solar cells (PSCs) under normal operation will reach a temperature above ~ 60 °C, across the tetragonal-cubic structural phase transition of methylammonium lead iodide (MAPbI 3). Whether the structural phase transition could result in dramatic changes of ionic, electrical and optical properties that may further impact the PSC performances should be studied. Herein, we report a structural phase transition temperature of MAPbI 3thin film at ~ 55 °C, but a striking contrast occurred at ~ 45 °C in the ionic and electrical properties of MAPbI 3due to a change of the ion activation energy from 0.7 eV tomore » 0.5 eV. The optical properties exhibited no sharp transition except for the steady increase of the bandgap with temperature. It was also observed that the activation energy for ionic migration steadily increased with increased grain sizes, and reduction of the grain boundary density reduced the ionic migration.« less

Low-temperature growth of aligned ZnO nanorods: effect of annealing gases on the structural and optical properties.

PubMed

Umar, Ahmad; Hahn, Yoon-Bong; Al-Hajry, A; Abaker, M

2014-06-01

Aligned ZnO nanorods were grown on ZnO/Si substrate via simple aqueous solution process at low-temperature of - 65 degrees C by using zinc nitrate and hexamethylenetetramine (HMTA). The detailed morphological and structural properties measured by FESEM, XRD, EDS and TEM confirmed that the as-grown nanorods are vertically aligned, well-crystalline possessing wurtzite hexagonal phase and grown along the [0001] direction. The room-temperature photoluminescence spectrum of the grown nanorods exhibited a strong and broad green emission and small ultraviolet emission. The as-prepared ZnO nanorods were post-annealed in nitrogen (N2) and oxygen (O2) environments and further characterized in terms of their morphological, structural and optical properties. After annealing the nanorods exhibit well-crystallinity and wurtzite hexagonal phase. Moreover, by annealing the PL spectra show the enhancement in the UV emission and suppression in the green emission. The presented results demonstrate that simply by post-annealing process, the optical properties of ZnO nanostructures can be controlled.

Structural and optical properties of electron-beam-evaporated ZnSe 1- x Te x Ternary compounds with various Te contents

NASA Astrophysics Data System (ADS)

Suthagar, J.; Suthan Kissinger, N. J.; Sharli Nath, G. M.; Perumal, K.

2014-01-01

ZnSe1- x Te x films with different tellurium (Te) contents were deposited by using an electron beam (EB) evaporation technique onto glass substrates for applications to optoelectronic devices. The structural and the optical properties of the ZnSe1- x Te x films were studied in the present work. The host material ZnSe1- x Te x , were prepared by using the physical vapor deposition method of the electron beam evaporation technique (PVD: EBE) under a pressure of 1 × 10-5 mbar. The X-ray diffractogram indicated that these alloy films had cubic structure with a strong preferential orientation of the crystallites along the (1 1 1) direction. The optical properties showed that the band gap (E g ) values varied from 2.73 to 2.41 eV as the tellurium content varied from 0.2 to 0.8. Thus the material properties can be altered and excellently controlled by controlling the system composition x.

The polarization response in InAs quantum dots: theoretical correlation between composition and electronic properties.

PubMed

Usman, Muhammad; Tasco, Vittorianna; Todaro, Maria Teresa; De Giorgi, Milena; O'Reilly, Eoin P; Klimeck, Gerhard; Passaseo, Adriana

2012-04-27

III-V growth and surface conditions strongly influence the physical structure and resulting optical properties of self-assembled quantum dots (QDs). Beyond the design of a desired active optical wavelength, the polarization response of QDs is of particular interest for optical communications and quantum information science. Previous theoretical studies based on a pure InAs QD model failed to reproduce experimentally observed polarization properties. In this work, multi-million atom simulations are performed in an effort to understand the correlation between chemical composition and polarization properties of QDs. A systematic analysis of QD structural parameters leads us to propose a two-layer composition model, mimicking In segregation and In-Ga intermixing effects. This model, consistent with mostly accepted compositional findings, allows us to accurately fit the experimental PL spectra. The detailed study of QD morphology parameters presented here serves as a tool for using growth dynamics to engineer the strain field inside and around the QD structures, allowing tuning of the polarization response.

Optical and structural properties of Mo-doped NiTiO3 materials synthesized via modified Pechini methods

NASA Astrophysics Data System (ADS)

Pham, Thanh-Truc; Kang, Sung Gu; Shin, Eun Woo

2017-07-01

In this study, molybdenum (Mo)-doped nickel titanate (NiTiO3) materials were successfully synthesized as a function of Mo content through a modified Pechini method followed by a solvothermal treatment process. Various characterization methods were employed to investigate the optical and structural properties of the materials. XRD patterns clearly showed that the NiTiO3 structure maintained a single phase with no observed crystalline structure transformations, even after the addition of 10 wt.% Mo. In the Raman spectra and XRD patterns, peak positions shifted with a change in Mo content, confirming that the NiTiO3 lattice was doped with Mo. On the other hand, Mo doping of NiTiO3 materials changed their optical properties. DRS-UV demonstrated that the addition of Mo increased photon absorption within the UV region. Relaxation processes were inhibited by Mo doping, which was evident in the PL spectra. Structural properties of the prepared materials were studied via FE-SEM and HR-TEM. The measured surface area increased proportionally with Mo content due to a reduction in grain size of the materials.

Modeling and properties of an ion-exchanged optical variable attenuator

NASA Astrophysics Data System (ADS)

Orignac, Xavier; Ingenhoff, Jan; Fabricius, Norbert

1999-03-01

The optical signal power needs to be regulated at some locations in transmission lines. That can be done with the help of optical variable attenuators (OVA), devices which allows for the control of their insertion loss. This work describes the design and properties of some OVAs fabricated by the ion-exchange technique. The OVA functionality relies on a Mach-Zehnder structure, where the output optical intensity is tuned via the change in optical path along one of the two interferometer arms. Here, the optical path is varied through thermo-optic effect (change of refractive index with temperature). Modelling is first addressed: a mostly qualitative theoretical investigation is used to clarify how the fabrication parameters (burial depth and Mach-Zehnder arm separation distance) can be related to the OVAs properties (attenuation dynamic, switching power, settling time, PDL). Properties of fabricated OVAs are presented in a second part. They are compared with other existing products. The relationship between fabrication parameters and properties is also re-examined in light of these results.

Plasma impact on structural, morphological and optical properties of copper acetylacetonate thin films.

PubMed

Abdel-Khalek, H; El-Samahi, M I; El-Mahalawy, Ahmed M

2018-06-15

The influence of plasma exposure on structural, morphological and optical properties of copper (II) acetylacetonate thin films deposited by thermal evaporation technique was investigated. Copper (II) acetylacetonate as-grown thin films were exposed to the atmospheric plasma for different times. The exposure of as-grown cu(acac) 2 thin film to atmospheric plasma for 5min modified its structural, morphological and optical properties. The effect of plasma exposure on structure and roughness of cu(acac) 2 thin films was evaluated by XRD and AFM techniques, respectively. The XRD results showed an increment in crystallinity due to exposure for 5min, but, when the exposure time reaches 10min, the film was transformed to an amorphous state. The AFM results revealed a strong modification of films roughness when the average roughness decreased from 63.35nm to ~1nm as a result of interaction with plasma. The optical properties of as-grown and plasma exposured cu(acac) 2 thin films were studied using spectrophotometric method. The exposure of cu(acac) 2 thin films to plasma produced the indirect energy gap decrease from 3.20eV to 2.67eV for 10min exposure time. The dispersion parameters were evaluated in terms of single oscillator model for as-grown and plasma exposured thin films. The influence of plasma exposure on third order optical susceptibility was studied. Copyright © 2018 Elsevier B.V. All rights reserved.

Detoxification of aflatoxins on prospective approach: effect on structural, mechanical, and optical properties under pressures.

PubMed

Wei, Yong-Kai; Zhao, Xiao-Miao; Li, Meng-Meng; Yu, Jing-Xin; Gurudeeban, Selvaraj; Hu, Yan-Fei; Ji, Guang-Fu; Wei, Dong-Qing

2018-06-01

Aflatoxins are sequential of derivatives of coumarin and dihydrofuran with similar chemical structures and well-known carcinogenic agent. Many studies performed to detoxify aflatoxins, but the result is not ideal. Therefore, we studied structural, infrared spectrum, mechanical, and optical properties of these compounds in the aim of perspective physics. Mulliken charge distributions and infrared spectral analysis performed to understand the structural difference between the basic types of aflatoxins. In addition, the effect of pressure, different polarized, and incident directions on their structural changes was determined. It is found that AFB 1 is most stable structure among four basic types aflatoxins (AFB 1 , AFB 2 , AFG 1 , and AFG 2 ), and IR spectra are analyzed to exhibit the difference on structures of them. The mechanical properties of AFB 1 indicate that the structure of this toxin can be easily changed by pressure. The real [Formula: see text] and imaginary [Formula: see text] parts of the dielectric function, and the absorption coefficient [Formula: see text] and energy loss spectrum [Formula: see text] were also obtained under different polarized and incident directions. Furthermore, biological experiments needed to support the toxic level of AFB 1 using optical technologies.

Structural and optical properties of nanostructured CdSe thin films prepared by electrochemical deposition

NASA Astrophysics Data System (ADS)

Bai, Rekha; Chaudhary, Sujeet; Pandya, Dinesh K.

2018-05-01

Cadmium selenide (CdSe) nanostructured thin films have been grown on fluorine doped tin oxide (FTO) coated glass substrates by potentiostatic electrochemical deposition (ECD) technique for use in solar energy conversion devices. The effect of bath temperature on the structural, morphological and optical properties of prepared CdSe films has been explored. X-ray diffraction (XRD) and Raman spectroscopy clearly show that the CdSe films are polycrystalline and exhibit phase transformation from wurtzite to zincblende structure with increase in bath temperature. Optical spectra reveal that the nanostructured CdSe films have high absorbance in visible region and the films show a red shift in direct optical energy band gap from 1.90 to 1.65 eV with increase in bath temperature due to change in phase and bandgap tuning related to quantum confinement effect.

Advanced optical measuring systems for measuring the properties of fluids and structures

NASA Technical Reports Server (NTRS)

Decker, A. J.

1986-01-01

Four advanced optical models are reviewed for the measurement of visualization of flow and structural properties. Double-exposure, diffuse-illumination, holographic interferometry can be used for three-dimensional flow visualization. When this method is combined with optical heterodyning, precise measurements of structural displacements or fluid density are possible. Time-average holography is well known as a method for displaying vibrational mode shapes, but it also can be used for flow visualization and flow measurements. Deflectometry is used to measure or visualize the deflection of light rays from collimation. Said deflection occurs because of refraction in a fluid or because of reflection from a tilted surface. The moire technique for deflectometry, when combined with optical heterodyning, permits very precise measurements of these quantities. The rainbow schlieren method of deflectometry allows varying deflection angles to be encoded with colors for visualization.

Aging effects of the precursor solutions on the properties of spin coated Ga-doped ZnO thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serrao, Felcy Jyothi, E-mail: jyothiserrao@gmail.com; Dharmaprakash, S. M.

2015-06-24

In this study, gallium doped zinc oxide thin films (GZO) were grown on a glass substrate by a simple sol-gel process and spin coating technique using zinc acetate and gallium nitrate (3at%) as precursors for Zn and Ga ions respectively. The effects of aging time of the precursor solution on the structural and optical properties of the GZO films were investigated. The surface morphology, grain size, film thickness and optical properties of the GZO films were found to depend directly on the sol aging time. XRD studies reveal that the films are polycrystalline with a hexagonal wurtzite structure and showmore » the c-axis grain orientation. Optical transmittance spectra of all the films exhibited transmittance higher than about 82% within the visible wavelength region. A sharp fundamental absorption edge with a slight blue shifting was observed with an increase in sol aging time which can be explained by Burstein-Moss effect. The result indicates that an appropriate aging time of the sol is important for the improvement of the structural and optical properties of GZO thin films derived from sol-gel method.« less

Elaboration and optimization of tellurite-based materials for raman gain application

NASA Astrophysics Data System (ADS)

Guery, Guillaume

Tellurite-based oxide glasses have been investigated as promising materials for Raman gain applications, due to their good linear and nonlinear optical properties and their wide transparency windows in the near- and midwave infrared spectral region. Furthermore, their interesting thermal properties, i.e. low glass transition temperature and ability to be drawn into optical fibers, make tellurite-based glasses excellent candidates for optical fiber amplifiers. The estimation of the strength and spectral distribution of Raman gain in materials is commonly approximated from the spontaneous Raman scattering cross-section measurement. For development of tellurite-based glasses as Raman amplifiers, understanding the relationship between glass structure, vibrational response, and nonlinear optical properties (NLO) represents a key point. This dissertation provides an answer to the fundamental question of the PhD study: "What is the impact of the glass structure on Raman gain properties of tellurite glasses?" This dissertation summarizes findings on different tellurite-based glass families: the TeO2-TaO5/2-ZnO, TeO2-BiO 3/2-ZnO and TeO2-NbO5/2 glass networks. The influence of glass modifiers has been shown on the glass' properties. Introduction of tantalum oxide or zinc oxide has been shown to increase the glass' stability against crystallization, quantified by DeltaT, where DeltaT = Tx -Tg. Added to the variation of the glass viscosity, this attribute is critical in fabricating optical fibers and for the use of these materials in fiber-based Raman gain applications. The role of ZnO in the tellurite network and the mechanism for structural modification has been determined. This addition results in not only the largest DeltaT reported for these highly nonlinear glasses to date, but coincides with a commensurate decrease of the refractive index. A hydroxyl purification has been developed that when employed, resulted in high purity preform materials exhibiting a limited absorption in the transmission bandwidth in the near infrared (NIR). A reduction of 90 % in the OH content in candidate glasses was realized and core-only optical fiber drawn from this glass exhibited optical losses lower than 10 dB/m (either at 1.55 mum or 2.0 mum). This optical attenuation in a high Raman gain material represents a first in the design of both material attributes. The role of the glass modifiers on the glass structure has been investigated by a combination of vibrational spectroscopic methods, including IR absorption, as well as Raman and hyper-Raman scatterings. Following examination of fundamental vibrations present in the paratellurite crystal alpha-TeO2, these results were extended to interpret the structure of multi-component tellurite glasses. It has been verified that the transformation of the tellurite entities TeO4→TeO3+1→TeO3 is directly related to the percentage and type of glass modifiers present in the various tellurite glass matrix. The dramatic disruption in the continuity of Te-O linkages in the tellurite glass backbone's chains during the introduction of the modifier zinc oxide, leads to a systematic reduction in glass network connectivity. This structural change is accompanied by a significant change in the glass' normalized polarization curve (IPsiV/IHV ), a paramter which quantifies directly the depolymerization ratio (DR). This metric provides direct correlation with a reduction in the ternary glass' polarizability/hyperpolarizability and a decrease in the glass' nonlinear optical properties, specifically its Raman gain response. These results have validated and extended our understanding of the important role of Te-O-Te content and short, medium and longer-scale organization of the tellurite glass network and the corresponding impact on linear and nonlinear optical response and properties. Such fundamental knowledge of the relationship between vibrational response and structure, correlated to linear and nonlinear optical properties, allows the extension of this know-how to the development of customized optical components enabled by novel glass and glass ceramic optical materials.

Structural and optical properties of WTe2 single crystals synthesized by DVT technique

NASA Astrophysics Data System (ADS)

Dixit, Vijay; Vyas, Chirag; Pathak, V. M.; Soalanki, G. K.; Patel, K. D.

2018-05-01

Layered transition metal di-chalcogenide (LTMDCs) crystals have attracted much attention due to their potential in optoelectronic device applications recently due to realization of their monolayer based structures. In the present investigation we report growth of WTe2 single crystals by direct vapor transport (DVT) technique. These crystals are then characterized by energy dispersive analysis of x-rays (EDAX) to study stoichiometric composition after growth. The structural properties are studied by x-ray diffraction (XRD) and selected area electron diffraction (SAED) is used to confirm orthorhombic structure of grown WTe2 crystal. Surface morphological properties of the crystals are also studied by scanning electron microscope (SEM). The optical properties of the grown crystals are studied by UV-Visible spectroscopy which gives direct band gap of 1.44 eV for grown WTe2 single crystals.

Theoretical exploration of structural, electro-optical and magnetic properties of gallium-doped silicon carbide nanotubes

NASA Astrophysics Data System (ADS)

Behzad, Somayeh; Chegel, Raad; Moradian, Rostam; Shahrokhi, Masoud

2014-09-01

The effects of gallium doping on the structural, electro-optical and magnetic properties of (8,0) silicon carbide nanotube (SiCNT) are investigated by using spin-polarized density functional theory. It is found from the calculation of the formation energies that gallium substitution for silicon atom is preferred. Our results show that gallium substitution at either single carbon or silicon atom site in SiCNT could induce spontaneous magnetization. The optical studies based on dielectric function indicate that new transition peaks and a blue shift are observed after gallium doping.

Multiwavelength Optical Switch Based on Controlling the Fermi Energy of Graphene

NASA Astrophysics Data System (ADS)

Jiang, Xiangqian; Bao, Jinlin; Sun, Xiudong

2018-04-01

We propose a graphene-dielectric-graphene corrugated structure to achieve a multiwavelength optical switch. The transmission and reflection properties of the structure are discussed, and multiultranarrow resonant peaks in the transmission and reflection spectra are found. By adjusting the Fermi energy of graphene, the resonant peaks will shift obviously. Based on this shifting property we present an active multiwavelength optical switch and achieve the on-off of four different wavelengths simultaneously. We also discuss the modulation depths of transmission and reflection. For the transmission of all four wavelengths we can get a very high modulation depth close to 100%.

Study of structural, elastic, electronic and optical properties of seven SrZrO{sub 3} phases: First-principles calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Qi-Jun, E-mail: dianerliu@yahoo.com.cn; Liu, Zheng-Tang; Feng, Li-Ping

2012-12-15

On the plane-wave ultrasoft pseudopotential technique based on the first-principles density functional theory (DFT), we calculated the structural, elastic, electronic and optical properties of the seven different phases of SrZrO{sub 3}. The obtained ground-state properties are in good agreement with previous experiments and calculations, which indicate that the most stable phase is orthorhombic Pnma structure. Seven phases of SrZrO{sub 3} are mechanically stable with cubic, tetragonal and orthorhombic structures. The mechanical and thermodynamic properties have been obtained by using the Voigt-Reuss-Hill approach and Debye-Grueneisen model. The electronic structures and optical properties are obtained and compared with the available experimental andmore » theoretical data. - Graphical abstract: Energy versus volume of seven phases SrZrO{sub 3} shows the Pnma phase has the minimum ground-state energy. Highlights: Black-Right-Pointing-Pointer We calculated the physical and chemical properties of seven SrZrO{sub 3} polymorphs. Black-Right-Pointing-Pointer The order of stability is Pnma>Imma>Cmcm>I4/mcm>P4/mbm>P4mm>Pm3-bar m. Black-Right-Pointing-Pointer The most stable phase is orthorhombic Pnma structure. Black-Right-Pointing-Pointer Seven phases of SrZrO{sub 3} are mechanically stable. Black-Right-Pointing-Pointer The relationship between n and {rho}{sub m} is n=1+0.18{rho}{sub m}.« less

Electronic Structures and Optical Properties of α-Al2O3Nanowires

NASA Astrophysics Data System (ADS)

Wang, Zhiqiang; Li, Chunlei; Liu, Lijia; Sham, Tsun-Kong

2013-04-01

The electronic structure and optical properties of α-Al2O3 nanowires (NWs) have been investigated using X-ray absorption near-edge structures (XANES) and X-ray excited optical luminescence (XEOL). The XANES were recorded in total electron yield (TEY) and total fluorescence yield (TFY) across the K- and L3,2-edges of aluminium and the K-edge of oxygen. The results indicate that the NWs are of a core/shell structure with a single-crystalline core and an amorphous shell. The XEOL spectra of the NWs show an intense peak at 404 nm, which comes from the F centre located in the amorphous shell of the NWs. The implication of these findings and the sensitivity of XEOL for defect detection are discussed.

Effect of disorder on the optical properties of short period superlattices

NASA Technical Reports Server (NTRS)

Strozier, J. A.; Zhang, Y. A.; Horton, C.; Ignatiev, A.; Shih, H. D.

1993-01-01

The optical properties of disordered short period superlattices are studied using a one-dimensional tight-binding model. A difference vector and disorder structure factor are proposed to characterize the disordered superlattice. The density of states, participation number, and optical absorption coefficients for both ordered and disordered superlattices are calculated as a function of energy. The results show that introduction of disorder into an indirect band gap material enhances the optical transition near the indirect band edge.

Optical properties of Si+ implanted PMMA

NASA Astrophysics Data System (ADS)

Balabanov, S.; Tsvetkova, T.; Borisova, E.; Avramov, L.; Bischoff, L.; Zuk, J.

2010-04-01

In the present work, low energy ion beam irradiation was used for surface modification of polymethyl-methacrylate (PMMA) using silicon (Si+) as the ion species. After high doses ion implantation of Si+ in the polymer material, a characterization of the optical properties was performed using optical transmission measurements in the visible and near infra-red (IR) wavelength range. The optical absorption increase observed with the ion dose was attributed to ion beam induced structural changes in the modified material.

Fundamental optical properties of linear and cyclic alkanes: VUV absorbance and index of refraction.

PubMed

Costner, Elizabeth A; Long, Brian K; Navar, Carlos; Jockusch, Steffen; Lei, Xuegong; Zimmerman, Paul; Campion, Alan; Turro, Nicholas J; Willson, C Grant

2009-08-20

VUV absorbance and index of refraction data for a series of linear and cyclic alkanes have been collected in order to understand the relationship between the electronic excitation wavelength (or absorbance edge), index of refraction, and molecular structure. The absorbance edge and index for a homologous series of both linear and cyclic alkanes increase with increasing carbon number. The optical properties of complex cycloalkanes do not vary predictably with increasing carbon number but instead depend on variations in the hydrocarbon structure in addition to hydrocarbon size. An understanding of the fundamental optical properties of this class of compounds is directly applicable to the identification of a high index and low-absorbance fluid for 193 nm immersion lithography.

Photovoltaic Performance of Inverted Polymer Solar Cells Using Hybrid Carbon Quantum Dots and Absorption Polymer Materials

NASA Astrophysics Data System (ADS)

Lim, Hwain; Lee, Kyu Seung; Liu, Yang; Kim, Hak Yong; Son, Dong Ick

2018-05-01

We report the synthesis and characterization of the carbon quantum dots (C-dots) easily obtained from citric acid and ethanediamine, and also investigated structural, optical and electrical properties. The C-dots have extraordinary optical and electrical features such as absorption of ultraviolet range and effective interface for charge separation and transport in active layer, which make them attractive materials for applications in photovoltaic devices (PV). The C-dots play important roles in charge extraction in the PV structures, they can be synthesized by a simple method and used to insert in active layer of polymer solar cells. In this study, we demonstrate that improve charge transport properties of inverted polymer solar cells (iPSCs) with C-dots and structural, optical and electrical properties of C-dots. As a result, iPSCs with C-dots showed enhancement of more than 30% compared with that of the contrast device in power conversion efficiency.

Characterization of Pb-Doped GaN Thin Films Grown by Thermionic Vacuum Arc

NASA Astrophysics Data System (ADS)

Özen, Soner; Pat, Suat; Korkmaz, Şadan

2018-03-01

Undoped and lead (Pb)-doped gallium nitride (GaN) thin films have been deposited by a thermionic vacuum arc (TVA) method. Glass and polyethylene terephthalate were selected as optically transparent substrates. The structural, optical, morphological, and electrical properties of the deposited thin films were investigated. These physical properties were interpreted by comparison with related analysis methods. The crystalline structure of the deposited GaN thin films was hexagonal wurtzite. The optical bandgap energy of the GaN and Pb-doped GaN thin films was found to be 3.45 eV and 3.47 eV, respectively. The surface properties of the deposited thin films were imaged using atomic force microscopy and field-emission scanning electron microscopy, revealing a nanostructured, homogeneous, and granular surface structure. These results confirm that the TVA method is an alternative layer deposition system for Pb-doped GaN thin films.

Experiment and density functional theory analyses of GdTaO4 single crystal

NASA Astrophysics Data System (ADS)

Ding, Shoujun; Kinross, Ashlie; Wang, Xiaofei; Yang, Huajun; Zhang, Qingli; Liu, Wenpeng; Sun, Dunlu

2018-05-01

GdTaO4 is a type of excellent materials that can be used as scintillation, laser matrix as well as self-activated phosphor has generated significant interest. Whereas its band structure, electronic structure and optical properties are still need elucidation. To solve this intriguing problem, high-quality GdTaO4 single crystal (M-type) was grown successfully using Czochralski method. Its structure as well as optical properties was determined in experiment. Moreover, a systematic theoretical calculation based on the density function theory methods were performed on M-type and M‧-type GdTaO4 and their band structure, density of state as well as optical properties were obtained. Combine with the performed experiment results, the calculated results were proved with high reliability. Hence, the calculated results obtained in this work could provide a deep understanding of GdTaO4 material, which also useful for the further investigation on GdTaO4 material.

Tomographic reconstruction of layered tissue structures

NASA Astrophysics Data System (ADS)

Hielscher, Andreas H.; Azeez-Jan, Mohideen; Bartel, Sebastian

2001-11-01

In recent years the interest in the determination of optical properties of layered tissue structure has resurfaced. Applications include, for example, studies on layered skin tissue and underlying muscles, imaging of the brain underneath layers of skin, skull, and meninges, and imaging of the fetal head in utero beneath the layered structures of the maternal abdomen. In this work we approach the problem of layered structures in the framework of model-based iterative image reconstruction schemes. These schemes are currently developed to determine the optical properties inside tissue from measurement on the surface. If applied to layered structure these techniques yield substantial improvements over currently available semi-analytical approaches.

Structural and optical properties improvements of PVP/gelatin blends induced by neutron irradiation

NASA Astrophysics Data System (ADS)

Basha, Mohammad Ahmad-Fouad; Hassan, Mohamed Ahmed

2018-05-01

Blends of polyvinylpyrrolidone and gelatin were prepared in three different concentrations to study the modifications in their structural and optical properties induced by neutron irradiations with different neutron fluence values from 108 up to 1011 neutron/cm2. X-ray spectroscopy revealed that the irradiation has induced a recrystallization phenomenon in the studied blends and the crystallinity index increased by increasing the neutron fluence due to the breaking of the crystallites. Fourier-transform infrared spectroscopy came to confirm the existence of interactions between interchain groups and a higher compatibility for the irradiated blends. The irradiation induced defects inside the material were responsible for the change in their optical and structural properties. The creation of free radicals or ions inside the conduction bands has led to the increase in the number of carriers on localized states; this has caused the increase in optical conductivity of the irradiated blends as a result of decreasing the energy gaps by increasing the neutron fluence. Results may widen the applications of the gelatin based blends to include optoelectronic devices, organic light emitting devices, solar selective and anti-reflectance bio-coatings, optical organic glass and lenses.

Wettability, structural and optical properties investigation of TiO{sub 2} nanotubular arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zalnezhad, E., E-mail: erfan@hanyang.ac.kr; Maleki, E.; Banihashemian, S.M.

2016-06-15

Graphical abstract: FESEM images of the TiO 2 nanotube layers formed at 0.5 wt% NH4F/ glycerol. - Highlights: • Structural property investigation of TiO{sub 2} nanotube. • Evaluation of wettability of TiO{sub 2} nanotube. • Study on optical properties of TiO{sub 2} nanotube. • The effect of anatase phase on optical and wettability properties of TiO{sub 2.} - Abstract: In this study, the effect of microstructural evolution of TiO{sub 2} nanotubular arrays on wettability and optical properties was investigated. Pure titanium was deposited on silica glass by PVD magnetron sputtering technique. The Ti coated substrates were anodized in an electrolytemore » containing NH{sub 4}F/glycerol. The structures of the ordered anodic TiO{sub 2} nanotubes (ATNs) as long as 175 nm were studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The result shows a sharp peak in the optical absorbance spectra around the band gap energy, 3.49–3.42 eV for annealed and non-annealed respectively. The thermal process induced growth of the grain size, which influence on the density of particles and the index of refraction. Furthermore, the wettability tests' result displays that the contact angle of intact substrate (θ = 74.7°) was decreased to 31.4° and 17.4° after anodization for amorphous and heat treated (450 °C) ANTs coated substrate, respectively.« less

Electronic and optical properties of nanocrystalline WO3 thin films studied by optical spectroscopy and density functional calculations

NASA Astrophysics Data System (ADS)

Johansson, Malin B.; Baldissera, Gustavo; Valyukh, Iryna; Persson, Clas; Arwin, Hans; Niklasson, Gunnar A.; Österlund, Lars

2013-05-01

The optical and electronic properties of nanocrystalline WO3 thin films prepared by reactive dc magnetron sputtering at different total pressures (Ptot) were studied by optical spectroscopy and density functional theory (DFT) calculations. Monoclinic films prepared at low Ptot show absorption in the near infrared due to polarons, which is attributed to a strained film structure. Analysis of the optical data yields band-gap energies Eg ≈ 3.1 eV, which increase with increasing Ptot by 0.1 eV, and correlate with the structural modifications of the films. The electronic structures of triclinic δ-WO3, and monoclinic γ- and ε-WO3 were calculated using the Green function with screened Coulomb interaction (GW approach), and the local density approximation. The δ-WO3 and γ-WO3 phases are found to have very similar electronic properties, with weak dispersion of the valence and conduction bands, consistent with a direct band-gap. Analysis of the joint density of states shows that the optical absorption around the band edge is composed of contributions from forbidden transitions (>3 eV) and allowed transitions (>3.8 eV). The calculations show that Eg in ε-WO3 is higher than in the δ-WO3 and γ-WO3 phases, which provides an explanation for the Ptot dependence of the optical data.

Fabrication of reduced graphene oxide nanosheets doped PVA composite films for tailoring their opto-mechanical properties

NASA Astrophysics Data System (ADS)

Aslam, Muhammad; Kalyar, Mazhar Ali; Raza, Zulfiqar Ali

2017-06-01

Laminar graphene nanosheets have raised passionate attention due to their incredible physico-chemical properties. Its wide-scale, high-yield production at low-cost has made it possible to produce top class promising versatile polymer nanocomposites. Reduced graphene oxide (RGO) nanosheets were incorporated to prepare optically tunable and high mechanical strength polymer nanocomposite films. RGO-doped poly(vinyl alcohol) (PVA) nanocomposite films were prepared via solution casting. Low level RGO doping significantly altered the structural, optical and mechanical properties of pure PVA films. Most of the band structure parameters like direct/indirect band gap, band tail, refractive index, dielectric constant, optical conductivity and dispersion parameters were investigated in detail for the first time. Tauc's, Wemple-DiDomenico, Helpin-Tsai and mixture rule models were employed to investigate optical and mechanical parameters. The applied models reinforced the experimental results in the present study. Advanced analytical techniques were engaged to characterize the nanocomposites films.

Modeling dispersive coupling and losses of localized optical and mechanical modes in optomechanical crystals

NASA Astrophysics Data System (ADS)

Eichenfield, Matt; Chan, Jasper; Safavi-Naeini, Amir H.; Vahala, Kerry J.; Painter, Oskar

2009-10-01

Periodically structured materials can sustain both optical and mechanical excitations which are tailored by the geometry. Here we analyze the properties of dispersively coupled planar photonic and phononic crystals: optomechanical crystals. In particular, the properties of co-resonant optical and mechanical cavities in quasi-1D (patterned nanobeam) and quasi-2D (patterned membrane) geometries are studied. It is shown that the mechanical Q and optomechanical coupling in these structures can vary by many orders of magnitude with modest changes in geometry. An intuitive picture is developed based upon a perturbation theory for shifting material boundaries that allows the optomechanical properties to be designed and optimized. Several designs are presented with mechanical frequency ~ 1-10 GHz, optical Q-factor Qo > 10^7, motional masses meff 100 femtograms, optomechanical coupling length LOM < 5 microns, and a radiation-limited mechanical Q-factor Qm > 10^7.

Crystal structure and electronic properties of a thiolate-protected Au24 nanocluster

NASA Astrophysics Data System (ADS)

Das, Anindita; Li, Tao; Li, Gao; Nobusada, Katsuyuki; Zeng, Chenjie; Rosi, Nathaniel L.; Jin, Rongchao

2014-05-01

Solving the total structures of gold nanoclusters is of critical importance for understanding their electronic, optical and catalytic properties. Herein, we report the X-ray structure of a charge-neutral Au24(SCH2Ph-tBu)20 nanocluster. This structure features a bi-tetrahedral Au8 kernel protected by four tetrameric staple-like motifs. Electronic structure analysis is further carried out and the optical absorption spectrum is interpreted. The Au24(SCH2Ph-tBu)20, Au23(S-c-C6H11)16 and Au25(SCH2CH2Ph)18 nanoclusters constitute the first crystallographically characterized ``trio''.Solving the total structures of gold nanoclusters is of critical importance for understanding their electronic, optical and catalytic properties. Herein, we report the X-ray structure of a charge-neutral Au24(SCH2Ph-tBu)20 nanocluster. This structure features a bi-tetrahedral Au8 kernel protected by four tetrameric staple-like motifs. Electronic structure analysis is further carried out and the optical absorption spectrum is interpreted. The Au24(SCH2Ph-tBu)20, Au23(S-c-C6H11)16 and Au25(SCH2CH2Ph)18 nanoclusters constitute the first crystallographically characterized ``trio''. Electronic supplementary information (ESI) available: Experimental and supporting Fig. S1-S3. CCDC NUMBER(1000102). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4nr01350f

Giant Optical Activity of Quantum Dots, Rods, and Disks with Screw Dislocations

NASA Astrophysics Data System (ADS)

Baimuratov, Anvar S.; Rukhlenko, Ivan D.; Noskov, Roman E.; Ginzburg, Pavel; Gun'Ko, Yurii K.; Baranov, Alexander V.; Fedorov, Anatoly V.

2015-10-01

For centuries mankind has been modifying the optical properties of materials: first, by elaborating the geometry and composition of structures made of materials found in nature, later by structuring the existing materials at a scale smaller than the operating wavelength. Here we suggest an original approach to introduce optical activity in nanostructured materials, by theoretically demonstrating that conventional achiral semiconducting nanocrystals become optically active in the presence of screw dislocations, which can naturally develop during the nanocrystal growth. We show the new properties to emerge due to the dislocation-induced distortion of the crystal lattice and the associated alteration of the nanocrystal’s electronic subsystem, which essentially modifies its interaction with external optical fields. The g-factors of intraband transitions in our nanocrystals are found comparable with dissymmetry factors of chiral plasmonic complexes, and exceeding the typical g-factors of chiral molecules by a factor of 1000. Optically active semiconducting nanocrystals—with chiral properties controllable by the nanocrystal dimensions, morphology, composition and blending ratio—will greatly benefit chemistry, biology and medicine by advancing enantiomeric recognition, sensing and resolution of chiral molecules.

Optical diffraction properties of multimicrogratings

DOE PAGES

Rothenbach, Christian A.; Kravchenko, Ivan I.; Gupta, Mool C.

2015-02-27

This paper shows the results of optical diffraction properties of multimicrograting structures fabricated by e-beam lithography. Multimicrograting consist of arrays of hexagonally shaped cells containing periodic one-dimensional (1D) grating lines in different orientations and arrayed to form large area patterns. We analyzed the optical diffraction properties of multimicrogratings by studying the individual effects of the several periodic elements of multimicrogratings. The observed optical diffraction pattern is shown to be the combined effect of the periodic and non-periodic elements that define the multimicrogratings and the interaction between different elements. We measured the total transverse electric (TE) diffraction efficiency of multimicrogratings andmore » found it to be 32.1%, which is closely related to the diffraction efficiency of 1D periodic grating lines of the same characteristics, measured to be 33.7%. Beam profiles of the optical diffraction patterns from multimicrogratings are captured with a CCD sensor technique. Interference fringes were observed under certain conditions formed by multimicrograting beams interfering with each other. Finally, these diffraction structures may find applications in sensing, nanometrology, and optical interconnects.« less

A novel approach to enhancement of surface properties of CdO films by using surfactant: dextrin

NASA Astrophysics Data System (ADS)

Sahin, Bünyamin; Bayansal, Fatih; Yüksel, Mustafa

2015-12-01

We studied the effect of an organic surfactant, dextrin, concentration on structural, morphological and optical properties of nanostructured CdO films deposited on glass substrates by using an easy and low-cost SILAR method. Microstructures of the nanostructured CdO films were optimized by adjusting dextrin concentration. XRD, SEM and UV-Vis Spectroscopy were used to study phase structure, surface morphology and optical properties of CdO films. Furthermore, effects of dextrin concentration on the surface roughness characteristics of CdO samples were reported. The results showed that the presence of organic surfactant highly affected the physical properties of CdO nanomaterials.

The Properties and Applications of Nanodiamonds.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mochalin, Vadym N.; Shenderova, Olga; Ho, Dean

Nanodiamonds have excellent mechanical and optical properties, high surface areas and tunable surface structures. They are also non-toxic, which makes them well suited to biomedical applications. Here we review the synthesis, structure, properties, surface chemistry and phase transformations of individual nanodiamonds and clusters of nanodiamonds. In particular we discuss the rational control of the mechanical, chemical, electronic and optical properties of nanodiamonds through surface doping, interior doping and the introduction of functional groups. These little gems have a wide range of potential applications in tribology, drug delivery, bioimaging and tissue engineering, and also as protein mimics and a filler materialmore » for nanocomposites.« less

The properties and applications of nanodiamonds.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mochalin, Vadym; Shenderova, Olga; Ho, Dean

Nanodiamonds have excellent mechanical and optical properties, high surface areas and tunable surface structures. They are also non-toxic, which makes them well suited to biomedical applications. Here we review the synthesis, structure, properties, surface chemistry and phase transformations of individual nanodiamonds and clusters of nanodiamonds. In particular we discuss the rational control of the mechanical, chemical, electronic and optical properties of nanodiamonds through surface doping, interior doping and the introduction of functional groups. These little gems have a wide range of potential applications in tribology, drug delivery, bioimaging and tissue engineering, and also as protein mimics and a filler materialmore » for nanocomposites.« less

Investigation of microstructure, micro-mechanical and optical properties of HfTiO{sub 4} thin films prepared by magnetron co-sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazur, Michal, E-mail: michal.mazur@pwr.edu.pl; Wojcieszak, Damian; Domaradzki, Jaroslaw

2015-12-15

Highlights: • HfTiO{sub 4} thin films were deposited by magnetron co-sputtering. • As-prepared and annealed at 800 °C thin films were nanocrystalline. • Optical properties and hardness were investigated in relation to thin films structure. • Hardness was 3-times higher in the case of as-deposited thin films. • HfTiO{sub 4} thin films are suitable for use as optical coatings with protective properties. - Abstract: Titania (TiO{sub 2}) and hafnium oxide (HfO{sub 2}) thin films are in the focus of interest to the microelectronics community from a dozen years. Because of their outstanding properties like, among the others, high stability, highmore » refractive index, high electric permittivity, they found applications in many optical and electronics domains. In this work discussion on the hardness, microstructure and optical properties of as-deposited and annealed HfTiO{sub 4} thin films has been presented. Deposited films were prepared using magnetron co-sputtering method. Performed investigations revealed that as-deposited coatings were nanocrystalline with HfTiO{sub 4} structure. Deposited films were built from crystallites of ca. 4–12 nm in size and after additional annealing an increase in crystallites size up to 16 nm was observed. Micro-mechanical properties, i.e., hardness and elastic modulus were determined using conventional load-controlled nanoindentation testing. the annealed films had 3-times lower hardness as-compared to as-deposited ones (∼9 GPa). Based on optical investigations real and imaginary components of refractive index were calculated, both for as-deposited and annealed thin films. The real refractive index component increased after annealing from 2.03 to 2.16, while extinction coefficient increased by an order from 10{sup −4} to 10{sup −3}. Structure modification was analyzed together with optical energy band-gap, Urbach energy and using Wemple–DiDomenico model.« less

Investigation of the electronic, magnetic and optical properties of newest carbon allotrope

NASA Astrophysics Data System (ADS)

Kazemi, Samira; Moradian, Rostam

2018-05-01

We investigate triple properties of monolayer pentagon graphene that include electronic, magnetic and optical properties based on density functional theory (DFT). Our results show that in the electronic and magnetic properties this structure with a direct energy gap of about 2.2 eV along Γ - Γ direction and total magnetic moment of 0.0013 μB per unit cell is almost a non-magnetic semiconductor. Also, its optical properties show that if this allotrope used in solar cell technology, its efficiency in the low energy will be better, because, in the range of energy, its loss energy function and reflectivity will be minimum.

Numerical study of the electronic structure, elastic and optical properties of defect quaternary semiconductor CuGaSnSe4

NASA Astrophysics Data System (ADS)

Shen, Kesheng; Lu, Hai; Zhang, Xianzhou; Jiao, Zhaoyong

2018-06-01

The electronic structure, elastic and optical properties of the defect quaternary semiconductor CuGaSnSe4 in I 4 bar structure are systematically investigated using first-principles calculations. We summarize and discuss some of the studies on CuGaSnSe4 in partially ordered chalcopyrite structure and find that there are three atomic arrangements so far, but it is still uncertain which is the most stable. Through detailed simulation and comparison with the corresponding literature, we get three models and predict that M1 model should be the most stable. The band structure and optical properties of compound CuGaSnSe4, including dielectric constant, refractive index and absorption spectrum, are drawn for a more intuitive understanding. The elastic constants are also calculated, which not only prove that CuGaSnSe4 in I 4 bar structure is stable naturally but also help solve the problem of no data to accurately predict axial thermal expansion coefficients. The calculated values of the zero frequency dielectric constant and refractive index are comparable to those of the corresponding chalcopyrite structure but slightly larger.

Atomistic Tight-Binding Theory Applied to Structural and Optical Properties of Silicon Nanodisks

NASA Astrophysics Data System (ADS)

Sukkabot, Worasak

2018-05-01

The use of ultrathin crystalline silicon (c-Si) wafers in solar cells necessitates a highly effective light absorber to compensate for poor light absorption. One route to overcoming this problem is to use a periodic array of Si nanodisks on ultrathin c-Si. In the present manuscript, we numerically investigate the effects of the geometrical parameters of the Si nanodisks, including disk diameter (D) and length (L), on the structural and optical properties, using atomistic tight-binding theory. These computations confirm that the electronic structure and optical properties are sensitive to the structural parameters. As the disk diameter and length increase, the single-electron energies decrease, and the single-hole energies increase. These calculations also reveal that, because of the quantum confinement effect, the optical band gaps gradually decrease independently of the increasing disk diameter and length. The optical spectra can be tuned across the visible region by varying the disk diameter and length, which is a useful feature for optimizing light absorption in solar cell applications. As the disk diameter and length increased, the optical intensities also increased; however, the atomistic electron-hole interactions and ground electron-hole wave function overlap progressively decreased. The ground electron-hole wave function overlap, Stokes shift, and fine structure splitting decreased as the disk diameter and length were increased. Thus, Si nanodisks with a large diameter and length might be a suitable candidate source of entangled photons. The Si nanodisks in this study also show promise for applications to solar cells based on ultrathin c-Si wafers.

Synthesis of liquid crystal silane-functionalized gold nanoparticles and their effects on the optical and electro-optic properties of a structurally related nematic liquid crystal.

PubMed

Mirzaei, Javad; Urbanski, Martin; Kitzerow, Heinz-S; Hegmann, Torsten

2014-05-19

Chemically and thermally robust liquid crystal silane-functionalized gold nanoparticles (i.e. AuNP1-AuNP3) were synthesized through silane conjugation. Colloidal dispersions of these particles with mesogenic ligands that are structurally identical (as in AuNP1, AuNP2) or compatible (as in AuNP3) with molecules of the nematic liquid crystal (N-LC) host showed superior colloidal stability and dispersibility. The thermal, optical, and electro-optic behaviors of the N-LC composites at different concentrations of each gold nanoparticle were investigated. All dispersions showed lower values for the rotational viscosity and elastic constant, but only AuNP3 with a dissimilar structure between the nanoparticle ligand and the host displayed the most drastic thermal effects and overall strongest impact on the electro-optic properties of the host. The observed results were explained considering both the structure and the density of the surface ligands of each gold nanoparticle. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal structure of Au25(SePh)18 nanoclusters and insights into their electronic, optical and catalytic properties

NASA Astrophysics Data System (ADS)

Song, Yongbo; Zhong, Juan; Yang, Sha; Wang, Shuxin; Cao, Tiantian; Zhang, Jun; Li, Peng; Hu, Daqiao; Pei, Yong; Zhu, Manzhou

2014-10-01

The crystal structure of selenolate-capped Au25(SePh)18- nanoclusters has been unambiguously determined for the first time, and provides a solid basis for a deeper understanding of the structure-property relationships. The selenolate-capped Au25 cluster shows noticeable differences from the previously reported Au25(SCH2CH2Ph)18- counterpart, albeit both share the icosahedral Au13 core and semi-ring Au2(SeR)3 or Au2(SR)3 motifs. Distinct differences in the electronic structure and optical, catalytic and electrochemical properties are revealed by the coupling experiments with density functional theory (TD-DFT) calculations. Overall, the successful determination of the Au25(SePh)18- structure removes any ambiguity about its structure, and comparison with the thiolated Au25 counterpart helps us to further understand how the ligands affect the properties of the nanocluster.The crystal structure of selenolate-capped Au25(SePh)18- nanoclusters has been unambiguously determined for the first time, and provides a solid basis for a deeper understanding of the structure-property relationships. The selenolate-capped Au25 cluster shows noticeable differences from the previously reported Au25(SCH2CH2Ph)18- counterpart, albeit both share the icosahedral Au13 core and semi-ring Au2(SeR)3 or Au2(SR)3 motifs. Distinct differences in the electronic structure and optical, catalytic and electrochemical properties are revealed by the coupling experiments with density functional theory (TD-DFT) calculations. Overall, the successful determination of the Au25(SePh)18- structure removes any ambiguity about its structure, and comparison with the thiolated Au25 counterpart helps us to further understand how the ligands affect the properties of the nanocluster. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04631e

The effect of mechanical drawing on optical and structural properties of nylon 6 fibres

NASA Astrophysics Data System (ADS)

El-Bakary, M. A.

2007-09-01

The Pluta polarizing double-refracting interference microscope was attached to a mechanical drawing device to study the effect of cold drawing on the optical and structural properties of nylon 6 fibres. The microscope was used in its two positions for determining the refractive indices and birefringence of fibres. Different applied stresses and strain rates were obtained using the mechanical-drawing device. The effect of the applied stresses on the optical and physical parameters was investigated. The resulting optical parameters were utilized to investigate the polarizability per unit volume, the optical orientation factor, the orientation angle and the average work per chain. The refractive index and birefringence profiles were measured. Relationships between the average work per chain and optical parameters at different strains rates were determined. An empirical formula was deduced for these fibres. Micro-interferograms are given for illustration.

The Effect of Sintering Temperature on Linear and Nonlinear Optical Properties of YAG Nanoceramics

NASA Astrophysics Data System (ADS)

Gayvoronsky, V. Ya.; Popov, A. S.; Brodyn, M. S.; Uklein, A. V.; Multian, V. V.; Shul'zhenko, O. O.

Recent improvements in powder synthesis and ceramics sintering made it possible to fabricate high-quality optical materials. The work is devoted to the structural and optical characterization of the ({Y_3}{Al_5}{O_{12}}, YAG) ceramics prepared by high-pressure low-temperature technique. The structural properties of the studied ceramic samples was obtained by X-ray diffraction. The studies of the total and in-line transmittance as well as optical scattering indicatrices were performed in visible and NIR ranges. The scatterer size ˜200 nm was estimated by Rayleigh-Gans-Debye model. It was shown that the studied samples demonstrate high transparency at 1064 nm. The nonlinear optical characterization of the samples was done by the self-action of the picosecond laser pulses at 1064 nm. The measured nonlinear optical response (χ^(3)) ˜ 10^{-11} esu) showed significant dependence on the sintering temperature variation.

A comparative density functional theory study of electronic structure and optical properties of γ-aminobutyric acid and its cocrystals with oxalic and benzoic acid

NASA Astrophysics Data System (ADS)

da Silva Filho, J. G.; Freire, V. N.; Caetano, E. W. S.; Ladeira, L. O.; Fulco, U. L.; Albuquerque, E. L.

2013-11-01

In this letter, we study the electronic structure and optical properties of the active medicinal component γ-aminobutyric acid (GABA) and its cocrystals with oxalic (OXA) and benzoic (BZA) acid by means of the density functional theory formalism. It is shown that the cocrystallization strongly weakens the zwitterionic character of the GABA molecule leading to striking differences among the electronic band structures and optical absorption spectra of the GABA crystal and GABA:OXA, GABA:BZA cocrystals, originating from distinct sets of hydrogen bonds. Calculated band widths and Δ-sol band gap estimates indicate that both GABA and GABA:OXA, GABA:BZA cocrystals are indirect gap insulators.

Effect of gamma radiation on low density polyethylene (LDPE) films: optical, dielectric and FTIR studies.

PubMed

Moez, A Abdel; Aly, S S; Elshaer, Y H

2012-07-01

The low density polyethylene (LDPE) films were irradiated with gamma radiation in the dose range varied from 20 to 400 kGy. The induced changes in the chemical structure and dielectric properties for the irradiated films were investigated. The structure modifications: crystallinity as well as possible molecular changes of the polymer were recognized using Fourier Transform Infrared Spectroscopy (FTIR). The optical results were determined from transmission, reflection and absorption spectra for these films. The dielectric properties of these films were calculated using optical methods. Result indicates small variation in crystallinity which could be increased or decreased depending on the relative importance of the structural and chemical changes. Copyright © 2012 Elsevier B.V. All rights reserved.

Structural, optical, morphological and electrical properties of undoped and Al-doped ZnO thin films prepared using sol—gel dip coating process

NASA Astrophysics Data System (ADS)

Boukhenoufa, N.; Mahamdi, R.; Rechem, D.

2016-11-01

In this work, sol—gel dip-coating technique was used to elaborate ZnO pure and ZnO/Al films. The impact of Al-doped concentration on the structural, optical, surface morphological and electrical properties of the elaborated samples was investigated. It was found that better electrical and optical performances have been obtained for an Al concentration equal to 5%, where the ZnO thin films exhibit a resistivity value equal to 1.64104 Ω·cm. Moreover, highest transparency has been recorded for the same Al concentration value. The obtained results from this investigation make the developed thin film structure a potential candidate for high optoelectronic performance applications.

Measuring the retina optical properties using a structured illumination imaging system

NASA Astrophysics Data System (ADS)

Basiri, A.; Nguyen, T. A.; Ibrahim, M.; Nguyen, Q. D.; Ramella-Roman, Jessica C.

2011-03-01

Patients with diabetic retinopathy (DR) may experience a reduction in retinal oxygen saturation (SO2). Close monitoring with a fundus ophthalmoscope can help in the prediction of the progression of disease. In this paper we present a noninvasive instrument based on structured illumination aimed at measuring the retina optical properties including oxygen saturation. The instrument uses two wavelngths one in the NIR and one visible, a fast acquisition camera, and a splitter system that allows for contemporaneous collection of images at two different wavelengths. This scheme greatly reduces eye movement artifacts. Structured illumination was achieved in two different ways, firstly several binary illumination masks fabricated using laser micro-machining were used, a near-sinusoidal projection pattern is ultimately achieved at the image plane by appropriate positioning of the binary masks. Secondarily a sinusoidal pattern printed on a thin plastic sheet was positioned at image plane of a fundus ophthalmoscope. The system was calibrated using optical phantoms of known optical properties as well as an eye phantom that included a 150μm capillary vessel containing different concentrations of oxygenated and deoxygenated hemoglobin.

Structural and optical properties of nanocrystalline ZnS and ZnS:Al films

NASA Astrophysics Data System (ADS)

Hurma, T.

2018-06-01

ZnS and ZnS:Al films have been deposited by ultrasonic spray pyrolysis (USP) method. Three different atomic ratios of aluminium were used as the dopant element. The effects of aluminum incorporation on structural and optical properties of the ZnS films have been investigated. The XRD analysis showed that the cubic structure of the ZnS was not much affected by Al doping. The crystal size of the films decreased, as the Al ratio increased. Al incorporation caused an increase in the intensity of ZnS films' peaks observed in Raman spectra and nearly symmetrical peaks were observed. Al doping caused a small decrease in optical band gap of the ZnS film. The coating of ZnS:Al films on the surface was quite good and there were not any deformation in their crystallization levels. Reflectance values of films are about 5% in the visible region but a little decrease is seen with aluminum doping. We can say that Al doping tends to improve the optical properties of the ZnS:Al films when compared with the undoped ZnS.

Effect of lead ion concentration on the structural and optical properties of nano-crystalline PbS thin films

NASA Astrophysics Data System (ADS)

Zaman, S.; Mehmood, S. K.; Mansoor, M.; Asim, M. M.

2014-06-01

PbS thin films have received considerable attention because of their potential applications in opto-electronics applications. Spontaneous reaction of lead acetate and thiourea in aqueous hydrazine hydrate has been used for depositing PbS thin films on glass substrates. Structural and optical properties of PbS thin films are greatly influenced by the morality of the reactants and crystal defects in the lattice. Our work focuses on the variation in lead ion concentration and its effect on the structural and optical properties of PbS thin films. The deposited films were analyzed using XRD, SEM, spectrophotometer and dark resistance measurement. XRD patterns indicated the formation of major phase of nano crystalline PbS with minor presence of lead oxide phase. We also noticed that peak intensity ratio of I111/I200 varied by changing the Pb ion concentration. The film thickness and dark resistance increased whereas optical band gap decreased with the decreasing Pb ion concentration. SEM scans showed that the grain size is less than 100 nm and is not affected by varying Pb ion concentration.

Comparative studies of structural, thermal, optical, and electrochemical properties of azines with different end groups with their azomethine analogues toward application in (opto)electronics.

PubMed

Sek, Danuta; Siwy, Mariola; Bijak, Katarzyna; Grucela-Zajac, Marzena; Malecki, Grzegorz; Smolarek, Karolina; Bujak, Lukasz; Mackowski, Sebastian; Schab-Balcerzak, Ewa

2013-10-10

Two series of azines and their azomethine analogues were prepared via condensation reaction of benzaldehyde, 2-hydroxybenzaldehyde, 4-pyridinecarboxaldehyde, 2-thiophenecarboxaldehyde, and 4-(diphenylamino)benzaldehyde with hydrazine monohydrate and 1,4-phenylenediamine, respectively. The structures of given compounds were characterized by FTIR, (1)H NMR, and (13)C NMR spectroscopy as well as elemental analysis. Optical, electrochemical, and thermal properties of all compounds were investigated by means of differential scanning calorimetry (DSC), UV-vis spectroscopy, stationary and time-resolved photoluminescence spectroscopy, and cycling voltammetry (CV). Additionally, the electronic properties, that is, orbital energies and resulting energy gap were calculated theoretically by density functional theory (DFT). Influence of chemical structure of the compounds on their properties was analyzed.

Annealing Temperature Dependent Structural and Optical Properties of RF Sputtered ZnO Thin Films.

PubMed

Sharma, Shashikant; Varma, Tarun; Asokan, K; Periasamy, C; Boolchandani, Dharmendar

2017-01-01

This work investigates the effect of annealing temperature on structural and optical properties of ZnO thin films grown over Si 100 and glass substrates using RF sputtering technique. Annealing temperature has been varied from 300 °C to 600 °C in steps of 100, and different microstructural parameters such as grain size, dislocation density, lattice constant, stress and strain have been evaluated. The structural and surface morphological characterization has been done using X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). XRD analysis reveals that the peak intensity of 002 crystallographic orientation increases with increased annealing temperature. Optical characterization of deposited films have been done using UV-Vis-NIR spectroscopy and photoluminescence spectrometer. An increase in optical bandgap of deposited ZnO thin films with increasing annealing temperature has been observed. The average optical transmittance was found to be more than 85% for all deposited films. Photoluminiscense spectra (PL) suggest that the crystalline quality of deposited film has increased at higher annealing temperature.

Nonlinear optical and G-Quadruplex DNA stabilization properties of novel mixed ligand copper(II) complexes and coordination polymers: Synthesis, structural characterization and computational studies

NASA Astrophysics Data System (ADS)

Rajasekhar, Bathula; Bodavarapu, Navya; Sridevi, M.; Thamizhselvi, G.; RizhaNazar, K.; Padmanaban, R.; Swu, Toka

2018-03-01

The present study reports the synthesis and evaluation of nonlinear optical property and G-Quadruplex DNA Stabilization of five novel copper(II) mixed ligand complexes. They were synthesized from copper(II) salt, 2,5- and 2,3- pyridinedicarboxylic acid, diethylenetriamine and amide based ligand (AL). The crystal structure of these complexes were determined through X-ray diffraction and supported by ESI-MAS, NMR, UV-Vis and FT-IR spectroscopic methods. Their nonlinear optical property was studied using Gaussian09 computer program. For structural optimization and nonlinear optical property, density functional theory (DFT) based B3LYP method was used with LANL2DZ basis set for metal ion and 6-31G∗ for C,H,N,O and Cl atoms. The present work reveals that pre-polarized Complex-2 showed higher β value (29.59 × 10-30e.s.u) as compared to that of neutral complex-1 (β = 0.276 × 10-30e.s.u.) which may be due to greater advantage of polarizability. Complex-2 is expected to be a potential material for optoelectronic and photonic technologies. Docking studies using AutodockVina revealed that complex-2 has higher binding energy for both G-Quadruplex DNA (-8.7 kcal/mol) and duplex DNA (-10.1 kcal/mol). It was also observed that structure plays an important role in binding efficiency.

Non-linear optical techniques and optical properties of condensed molecular systems

NASA Astrophysics Data System (ADS)

Citroni, Margherita

2013-06-01

Structure, dynamics, and optical properties of molecular systems can be largely modified by the applied pressure, with remarkable consequences on their chemical stability. Several examples of selective reactions yielding technologically attractive products can be cited, which are particularly efficient when photochemical effects are exploited in conjunction with the structural conditions attained at high density. Non-linear optical techniques are a basic tool to unveil key aspects of the chemical reactivity and dynamic properties of molecules. Their application to high-pressure samples is experimentally challenging, mainly because of the small sample dimensions and of the non-linear effects generated in the anvil materials. In this talk I will present results on the electronic spectra of several aromatic crystals obtained through two-photon induced fluorescence and two-photon excitation profiles measured as a function of pressure (typically up to about 25 GPa), and discuss the relationship between the pressure-induced modifications of the electronic structure and the chemical reactivity at high pressure. I will also present the first successful pump-probe infrared measurement performed as a function of pressure on a condensed molecular system. The system under examination is liquid water, in a sapphire anvil cell, up to 1 GPa along isotherms at 298 and 363 K. These measurements give a new enlightening insight into the dynamical properties of low- and high-density water allowing a definition of the two structures.

Reflection Spectra of Distorted Cholesteric Liquid Crystal Structures in Cells with Interdigitated Electrodes (Postprint)

DTIC Science & Technology

2014-07-01

adjusting the magnitude of the electric field. 15. SUBJECT TERMS liquid crystals , liquid- crystal devices, Bragg reflectors, optical properties, chiral ...160.3710) Liquid crystals ; (230.3720) Liquid- crystal devices; (230.1480) Bragg reflectors; (160.4760) Optical properties; (160.1585) Chiral media...White, and T. J. Bunning, “Local optical spectra and texture for chiral nematic liquid crystals in cells with interdigitated electrodes,” Mol

Spectroscopic and fiber optic ethanol sensing properties Gd doped ZnO nanoparticles.

PubMed

Noel, J L; Udayabhaskar, R; Renganathan, B; Muthu Mariappan, S; Sastikumar, D; Karthikeyan, B

2014-11-11

We report the structural, optical and gas sensing properties of prepared pure and Gd doped ZnO nanoparticles through solgel method at moderate temperature. Structural studies are carried out by X-ray diffraction method confirms hexagonal wurtzite structure and doping induced changes in lattice parameters is observed. Optical absorption spectral studies shows red shift in the absorption peak corresponds to band-gap from 3.42 eV to 3.05 eV and broad absorption in the visible range after Gd doping is observed. Scanning electron microscopic studies shows increase in particle size where the particle diameters increase from few nm to micrometers after Gd doping. The clad modified ethanol fiber-optic sensor studies for ethanol sensing exhibits best sensitivity for the 3% Gd doped ZnO nanoparticles and the sensitivity get lowered incase of higher percentage of Gd doped ZnO sample. Copyright © 2014 Elsevier B.V. All rights reserved.

Electronic structure and optical properties of GdNi2Mnx compounds

NASA Astrophysics Data System (ADS)

Knyazev, Yu. V.; Lukoyanov, A. V.; Kuz'min, Yu. I.; Gaviko, V. S.

2018-02-01

The electronic structure and optical properties of GdNi2Mnx compounds (x = 0, 0.4, 0.6) were investigated. Spin-polarized electronic structure calculations were performed in the approximation of local electron spin density corrected for strong electron correlations using the LSDA+U method. The changes in the magnetic moments and exchange interactions in GdNi2Mnx (x = 0, 0.4, 0.6) governing the increase in the Curie temperature with manganese concentration were determined. The optical constants of the compounds were measured by the ellipsometric method in the wide spectral range of 0.22-15 μm. The peculiarities of the evolution of the frequency dependences of optical conductivity with a change in the manganese content were revealed. Based on the calculated densities of electron states, the behavior of these dispersion curves in the region of interband absorption of light was discussed. The concentration dependences of several electronic characteristics were determined.

Structural and optical properties of PbS thin films grown by chemical bath deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seghaier, S.; Kamoun, N.; Guasch, C.

2007-09-19

Lead sulphide thin films are grown on glass substrates at various deposition times tD, in the range of 40-60 min per step of 2 min, using the chemical bath deposition technique. X-ray diffraction and atomic force microscopy are used to characterize the film structure. The surface composition is analysed by Auger electron spectroscopy. It appears that the as-prepared thin films are polycrystalline with cubic structure. Nanometric scale crystallites are uniformly distributed on the surface. They exhibit almost a stoechiometric composition with a [Pb]/[S] ratio equal to 1.10. Optical properties are studied in the range of 300-3300 nm by spectrophotometric measurements.more » Analysis of the optical absorption data of lead sulphide thin layers reveals a narrow optical direct band gap equal to 0.46 eV for the layer corresponding to a deposition time equal to 60 min.« less

Optical properties of the Tietz-Hua quantum well under the applied external fields

NASA Astrophysics Data System (ADS)

Kasapoglu, E.; Sakiroglu, S.; Ungan, F.; Yesilgul, U.; Duque, C. A.; Sökmen, I.

2017-12-01

In this study, the effects of the electric and magnetic fields as well as structure parameter- γ on the total absorption coefficient, including linear and third order nonlinear absorption coefficients for the optical transitions between any two subband in the Tietz-Hua quantum well have been investigated. The optical transitions were investigated by using the density matrix formalism and the perturbation expansion method. The Tietz-Hua quantum well becomes narrower (wider) when the γ - structure parameter increases (decreases) and so the energies of the bound states will be functions of this parameter. Therefore, we can provide the red or blue shift in the peak position of the absorption coefficient by changing the strength of the electric and magnetic fields as well as the structure parameters and these results can be used to adjust and control the optical properties of the Tietz-Hua quantum well.

Experimental study of optical and electrical properties of ZnO nano composites electrodeposited on n-porous silicon substrate for photovoltaic applications

NASA Astrophysics Data System (ADS)

Selmane, Naceur; Cheknane, Ali; Gabouze, Nourddine; Maloufi, Nabila; Aillerie, Michel

2017-11-01

ZnO films deposited on silicon porous substrates (PS) were prepared by electro-deposition anodization on n type (100) silicon wafer. This ZnO/PS structure combines substrates having specific structural and optical properties (IR emission), with nano-composites of ZnO potentially interesting due to their functional properties (UV emission) to be integrated as constitutive elements of devices in various optoelectronic applications mainly in blue light emitters. With this combined structure, the blue shift in the PL peak is possible and easy to obtain (467nm). The vibration modes of PS and ZnO films on PS substrates (ZnO /PS) were investigated by infrared (FTIR) measurements and their behaviors were analyzed and discussed by considering the structural properties characterized by X-ray diffraction (DRX) and scanning electronic microscopy (MEB).

Influences of film thickness on the structural, electrical and optical properties of CuAlO2 thin films

NASA Astrophysics Data System (ADS)

Dong, Guobo; Zhang, Ming; Wang, Mei; Li, Yingzi; Gao, Fangyuan; Yan, Hui; Diao, Xungang

2014-07-01

CuAlO2 films with different thickness were prepared by the radio frequency magnetron sputtering technique. The structural, electrical and optical properties of CuAlO2 were studied by X-ray diffraction, atomic force microscope, UV-Vis double-beam spectrophotometer and Hall measurements. The results indicate that the single phase hexagonal CuAlO2 is formed and the average grain size of CuAlO2 films increases with increasing film thickness. The results also exhibit that the lowering of bandgap and the increase of electrical conductivity of CuAlO2 films with the increase of their thickness, which are attributed to the improvement of the grain size and the anisotropic electrical property. According to the electrical and optical properties, the biggest figure of merit is achieved for the CuAlO2 film with the appropriate thickness of 165 nm.

Effect of thermal annealing on structural and optical properties of In{sub 2}S{sub 3} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choudhary, Sonu, E-mail: sonuchoudhary1983@gmail.com

2015-08-28

There is a highly need of an alternate of toxic materials CdS for solar cell applications and indium sulfide is found the most suitable candidate to replace CdS due to its non-toxic and environmental friendly nature. In this paper, the effect of thermal annealing on the structural and optical properties of indium sulfide (In{sub 2}S{sub 3}) thin films is undertaken. The indium sulfide thin films of 121 nm were deposited on glass substrates employing thermal evaporation method. The films were subjected to the X-ray diffractometer and UV-Vis spectrophotometer respectively for structural and optical analysis. The XRD pattern show that themore » as-deposited thin film was amorphous in nature and crystallinity is found to be varied with annealing temperature. The optical analysis reveals that the optical band gap is varied with annealing. The optical parameters like absorption coefficient, extinction coefficient and refractive index were calculated. The results are in good agreement with available literature.« less

Influence of Lanthanum Doping on the Structural and Optical Properties of Hematite Nanopowders

NASA Astrophysics Data System (ADS)

Justus, J. Sharmila; Dharma Roy, S. Dawn; Raj, A. Moses Ezhil

2016-10-01

Rare-earth elements are an attractive class of dopant elements, as they give easily trivalent cations that possibly altering the structure and other properties of the parent nanoparticles and creating multifunctional materials because of their f-electronic configurations. Herein, experimental evidence has been given for a better understanding of the factors that dictate the interactions of La doping on the structure and optical properties of iron oxide nanoparticles. For that, lanthanum doped hematite (α-Fe2O3) nanoparticles were prepared by a facile solution method using iron (III) chloride (FeCl3) as starting precursor and sodium hydroxide (NaOH) as reducing agent without templates at low temperature. As-prepared powders were subsequently calcined in air for 3 hr at 800 °C. Xray diffraction (XRD) technique was used to study the nanocrystal formation of α-Fe2O3 and Fourier Transform Raman (FT-Raman) spectral information identified the chemical bond structure of the nanoparticles. Morphology study of the nanoparticles was identified using Scanning Electron Microscope (SEM) and the incorporated La content was recognized from the Energy Dispersive X-ray Spectroscopy (EDS) analysis. The optical absorption spectrum was recorded in the wavelength range of 200-2000 nm and the optical parameters such as absorption coefficient and optical band gap energy of pure and doped Fe2O3 nanoparticles were determined. Obtained results are interpreted by considering the impregnation of trivalent La cations that replaced Fe cations of the host structure.

Three-dimensional surface profile intensity correction for spatially modulated imaging

NASA Astrophysics Data System (ADS)

Gioux, Sylvain; Mazhar, Amaan; Cuccia, David J.; Durkin, Anthony J.; Tromberg, Bruce J.; Frangioni, John V.

2009-05-01

We describe a noncontact profile correction technique for quantitative, wide-field optical measurement of tissue absorption (μa) and reduced scattering (μs') coefficients, based on geometric correction of the sample's Lambertian (diffuse) reflectance intensity. Because the projection of structured light onto an object is the basis for both phase-shifting profilometry and modulated imaging, we were able to develop a single instrument capable of performing both techniques. In so doing, the surface of the three-dimensional object could be acquired and used to extract the object's optical properties. The optical properties of flat polydimethylsiloxane (silicone) phantoms with homogenous tissue-like optical properties were extracted, with and without profilometry correction, after vertical translation and tilting of the phantoms at various angles. Objects having a complex shape, including a hemispheric silicone phantom and human fingers, were acquired and similarly processed, with vascular constriction of a finger being readily detectable through changes in its optical properties. Using profilometry correction, the accuracy of extracted absorption and reduced scattering coefficients improved from two- to ten-fold for surfaces having height variations as much as 3 cm and tilt angles as high as 40 deg. These data lay the foundation for employing structured light for quantitative imaging during surgery.

Fiber optic sensor technology - An opportunity for smart aerospace structures

NASA Technical Reports Server (NTRS)

Heyman, J. S.; Rogowski, R. S.; Claus, R. O.

1988-01-01

Fiber optic sensors provide the opportunity for fabricating materials with internal sensors which can serve as lifetime health monitors, analogous to a central nervous system. The embedded fiber optic sensors can be interrogated by various techniques to measure internal strain, temperature, pressure, acoustic waves and other parameters indicative of structural integrity. Experiments have been conducted with composite samples with embedded sensors to measure strain using optical time domain reflectometry, modal interference and an optical phase locked loop. Fiber optic sensors have been developed to detect acoustic emission and impact damage and have been demonstrated for cure monitoring. These sensors have the potential for lifetime monitoring of structural properties, providing real time nondestructive evaluation.

A theoretical study of the non-linear optical properties of a series of Ni-dithiolene derivatives

NASA Astrophysics Data System (ADS)

Avramopoulos, Aggelos; Papadopoulos, Manthos G.

2015-01-01

The linear and nonlinear optical properties of a series of nickel derivatives have been studied. The results have been verified and interpreted by employing a series of methods (e.g. UCCSD(T), CASSCF/CASPT2). The diradicaloid character of Ni ( SCH )4 is discussred. The effect on the properties of changes in the structure of NiBDT is analysed.

Photonic Resins: Designing Optical Appearance via Block Copolymer Self-Assembly.

PubMed

Song, Dong-Po; Jacucci, Gianni; Dundar, Feyza; Naik, Aditi; Fei, Hua-Feng; Vignolini, Silvia; Watkins, James J

2018-03-27

Despite a huge variety of methodologies having been proposed to produce photonic structures by self-assembly, the lack of an effective fabrication approach has hindered their practical uses. These approaches are typically limited by the poor control in both optical and mechanical properties. Here we report photonic thermosetting polymeric resins obtained through brush block copolymer (BBCP) self-assembly. We demonstrate that the control of the interplay between order and disorder in the obtained photonic structure offers a powerful tool box for designing the optical appearance of the polymer resins in terms of reflected wavelength and scattering properties. The obtained materials exhibit excellent mechanical properties with hardness up to 172 MPa and Young's modulus over 2.9 GPa, indicating great potential for practical uses as photonic coatings on a variety of surfaces.

Numerical calculation of phase-matching properties in photonic crystal fibers with three and four zero-dispersion wavelengths.

PubMed

Zhao, Xingtao; Liu, Xiaoxu; Wang, Shutao; Wang, Wei; Han, Ying; Liu, Zhaolun; Li, Shuguang; Hou, Lantian

2015-10-19

Photonic crystal fibers with three and four zero-dispersion wavelengths are presented through special design of the structural parameters, in which the closing to zero and ultra-flattened dispersion can be obtained. The unique phase-matching properties of the fibers with three and four zero-dispersion wavelengths are analyzed. Variation of the phase-matching wavelengths with the pump wavelengths, pump powers, dispersion properties, and fiber structural parameters is analyzed. The presence of three and four zero-dispersion wavelengths can realize wavelength conversion of optical soliton between two anomalous dispersion regions, generate six phase-matching sidebands through four-wave mixing and create more new photon pairs, which can be used for the study of supercontinuum generation, optical switches and quantum optics.

Effect of Varying Pnictogen Elements (Pn=N, P, As, Sb, Bi) on the Optoelectronic Properties of SrZn2Pn2

NASA Astrophysics Data System (ADS)

Murtaza, G.; Yousaf, N.; Laref, A.; Yaseen, M.

2018-03-01

Pnictogen-based Zintl compounds have fascinating properties. Nowadays these compounds have gained exceptional interest in thermoelectric and optoelectronic fields. Therefore, in this work the structural, electronic and optical properties of SrZn2Pn2 (Pn=N, P, As, Sb, Bi) compounds were studied using state-of-the-art density functional theory. The optimised lattice parameters (ɑ, c, c/ɑ and bond lengths) are consistent with the experimental results. The bulk moduli and c/a showed a decrease when changing the Pnictogen (Pn) anion from N to Bi in SrZn2Pn2 (Pn=N, P, As, Sb, Bi). The modified Becke-Johnson potential is used for band structure calculations. All compounds show semiconducting behaviour except SrZn2Bi2, which is metallic. Pn-p, Zn-d and Sr-d play an important role in defining the electronic structure of the compounds. The optical conductivity and absorption coefficient strength are high in visible and ultraviolet regions. These band structures and optical properties clearly show that SrZn2Pn2 compounds are potential candidates in the fields of optoelectronic and photonic devices.

Effect of CTAB on structural and optical properties of CuO nanoparticles prepared by coprecipitation route

NASA Astrophysics Data System (ADS)

Varghese, Donna; Tom, Catherine; Krishna Chandar, N.

2017-11-01

CuO (Copper Oxide) nanoparticles were synthesized by a simple coprecipitation route by using copper acetate, sodium hydroxide as precursors and cetyltrimethyl ammonium bromide (CTAB) as surfactant. For the purpose of the study, the surfactant-CTAB treated and non-treated samples were synthesized separately. Both the synthesized samples were studied to understand their structural and optical properties. The formation of CuO and its crystallinity was confirmed by XRD. Further, the optical studies showed a defined blue shift in CTAB treated sample which is clear evidence that the particles undergo confinement when they are nano-regime.

Cross-linked polyimides for integrated optics

NASA Astrophysics Data System (ADS)

Singer, Kenneth D.; Kowalczyk, Tony C.; Nguyen, Hung D.; Beuhler, Allyson J.; Wargowski, David A.

1997-01-01

We have investigated a promising class of polyimide materials for both passive and active electro-optic devices, namely crosslinkable polyimides. These fluorinated polyimides are soluble in the imidized form and are both thermally and photo-crosslinkable leading to easy processability into waveguide structures and the possibility of stable electro-optic properties. We have fabricated channel and slab waveguides and investigated the mechanism of optical propagation loss using photothermal deflection spectroscopy and waveguide loss spectroscopy, and found the losses to arise from residual absorption due to the formation of charge transfer states. The absorption is inhibited by fluorination leading to propagation losses as low as 0.3 dB/cm in the near infrared. Because of the ability to photocrosslink, channel waveguides are fabricated using a simple wet-etch process. Channel waveguides so formed are observed to have no excess loss over slab structures. Solubility followed by thermal cross-linking allows the formation of multilayer structures. We have produced electro-optic polymers by doping with the nonlinear optical chromophores, DCM and DADC; and a process of concurrent poling and thermal crosslinking. Multilayer structures have been investigated and poling fields optimized in the active layer by doping the cladding with an anti-static agent. The high glass-transition temperature and cross-linking leads to very stable electro-optic properties. We are currently building electro-optic modulators based on these materials. Progress and results in this area also are reported.

Investigation of optical properties of multilayer dielectric structures using prism-coupling technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sokolov, V I; Glebov, V N; Malyutin, A M

2015-09-30

A method based on resonant excitation of waveguide modes with a prism coupler is proposed for measuring the thickness and refractive index of thin-film layers in multilayer dielectric structures. The peculiarities of reflection of TE- and TM-polarised light beams from a structure comprising eleven alternating layers of zinc sulfide (ZnS) and magnesium barium fluoride (MgBaF{sub 4}), whose thicknesses are much less than the wavelength of light, are investigated. Using the mathematical model developed, we have calculated the coefficients of reflection of collimated TE and TM light beams from a multilayer structure and determined the optical constants and thicknesses of themore » structure layers. The refractive indices of the layers, obtained for TE and TM polarisation of incident light, are in good agreement. The thicknesses of ZnS and MgBaF{sub 4} layers, found for different polarisations, coincide with an accuracy of ±1%. Thus, we have demonstrated for the first time that the prism-coupling technique allows one to determine the optical properties of thin-film structures when the number of layers in the structure exceeds ten layers. (integrated optics)« less

Thermodynamical and thermoelectric properties of boron doped YPd{sub 3} and YRh{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dwivedi, Shalini; Sharma, Yamini, E-mail: sharma.yamini62@gmail.com; Sharma, Ramesh

2016-05-23

The structural, electronic, thermal, and optical properties of borides of cubic non-magnetic YX{sub 3} (X=Rh, Pd) compounds and their borides which crystallize in the AuCu{sub 3} structure have been studied using the density functional theory (DFT). The flat bands in the vicinity of E{sub F} which are associated with superconductivity appear in YPd{sub 3} and YRh{sub 3} band structures. However, the B s-states enhance the flat band only in YRh{sub 3}B. The optical properties clearly show that boron insertion modifies the absorption and transmittance. The YX{sub 3} alloys and their borides exhibit valuable changes in the thermopower and ZT. Itmore » is observed that the properties of the Y-X intermetallics change significantly for the Y-Rh and Y-Pd alloys and the presence of single boron atom modifies the properties to a great extent.« less

Titanium dioxide thin films deposited by pulsed laser deposition and integration in radio frequency devices: Study of structure, optical and dielectric properties

NASA Astrophysics Data System (ADS)

Orlianges, Jean-Christophe; Crunteanu, Aurelian; Pothier, Arnaud; Merle-Mejean, Therese; Blondy, Pierre; Champeaux, Corinne

2012-12-01

Titanium dioxide presents a wide range of technological application possibilities due to its dielectric, electrochemical, photocatalytic and optical properties. The three TiO2 allotropic forms: anatase, rutile and brookite are also interesting, since they exhibit different properties, stabilities and growth modes. For instance, rutile has a high dielectric permittivity, of particular interest for the integration as dielectric in components such as microelectromechanical systems (MEMS) for radio frequency (RF) devices. In this study, titanium dioxide thin films are deposited by pulsed laser deposition. Characterizations by Raman spectroscopy and X-ray diffraction show the evolution of the structural properties. Thin films optical properties are investigated using spectroscopic ellipsometry and transmission measurements from UV to IR range. Co-planar waveguide (CPW) devices are fabricated based on these films. Their performances are measured in the RF domain and compared to simulation, leading to relative permittivity values in the range 30-120, showing the potentialities of the deposited material for capacitive switches applications.

Facile growth of barium oxide nanorods: structural and optical properties.

PubMed

Ahmad, Naushad; Wahab, Rizwan; Alam, Manawwer

2014-07-01

This paper reports a large-scale synthesis of barium oxide nanorods (BaO-NRs) by simple solution method at a very low-temperature of - 60 degrees C. The as-grown BaO-NRs were characterized in terms of their morphological, structural, compositional, optical and thermal properties. The morphological characterizations of as-synthesized nanorods were done by scanning electron microscopy (SEM) which confirmed that the synthesized products are rod shaped and grown in high density. The nanorods exhibits smooth and clean surfaces throughout their lengths. The crystalline property of the material was analyzed with X-ray diffraction pattern (XRD). The compositional and thermal properties of synthesized nanorods were observed via Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis which confirmed that the synthesized nanorods are pure BaO and showed good thermal stability. The nanorods exhibited good optical properties as was confirmed from the room-temperature UV-vis spectroscopy. Finally, a plausible mechanism for the formation of BaO-NRs is also discussed in this paper.

Effects of oxidation on the plasmonic properties of aluminum nanoclusters.

PubMed

Douglas-Gallardo, Oscar A; Soldano, Germán J; Mariscal, Marcelo M; Sánchez, Cristián Gabriel

2017-11-16

The scouting of alternative plasmonic materials able to enhance and extend the optical properties of noble metal nanostructures is on the rise. Aluminum is endowed with a set of interesting properties which turn it into an attractive plasmonic material. Here we present the optical and electronic features of different aluminum nanostructures stemming from a multilevel computational study. Molecular Dynamics (MD) simulations using a reactive force field (ReaxFF), carefully validated with Density Functional Theory (DFT), were employed to mimic the oxidation of icosahedral aluminum nanoclusters. Resulting structures with different oxidation degrees were then studied through the Time-Dependent Density Functional Tight Binding (TD-DFTB) method. A similar approach was used in aluminum nanoclusters with a disordered structure to study how the loss of crystallinity affects the optical properties. To the best of our knowledge, this is the first report that addresses this issue from the fully atomistic time-dependent approach by means of two different and powerful simulation tools able to describe quantum and physicochemical properties associated with nanostructured particles.

Synthesis, structural and optical properties of (ALa)(FeMn)O6 (A = Ba and Sr) double perovskites

NASA Astrophysics Data System (ADS)

Kumar, Dinesh; Sudarshan, V.; Singh, Akhilesh Kumar

2018-05-01

Here, we report structural and optical properties of ALaFeMnO6 (A = Ba and Sr) double perovskite synthesized via auto-combustion followed by calcinations process. Rietveld refinement of structure using x-ray diffraction data reveals that BaLaFeMnO6 crystallizes into cubic crystal structure with space group Pm-3m while SrLaFeMnO6 crystallizes into rhombohedral crystal structure having space group R-3c. The absorption spectrum measurement using UV-Vis spectroscopy reveals that these samples are prefect insulator having energy band gap between conduction and valence band of the order of 6 eV.

Development of the α-IGZO/Ag/α-IGZO Triple-Layer Structure Films for the Application of Transparent Electrode.

PubMed

Chen, Kun-Neng; Yang, Cheng-Fu; Wu, Chia-Ching; Chen, Yu-Hsin

2017-02-24

We investigated the structural, optical, and electrical properties of amorphous IGZO/silver/amorphous IGZO (α-IGZO/Ag/α-IGZO) triple-layer structures that were deposited at room temperature on Eagle XG glass and flexible polyethylene terephthalate substrates through the sputtering method. Thin Ag layers with different thicknesses were inserted between two IGZO layers to form a triple-layer structure. Ag was used because of its lower absorption and resistivity. Field emission scanning electron microscopy measurements of the triple-layer structures revealed that the thicknesses of the Ag layers ranged from 13 to 41 nm. The thickness of the Ag layer had a large effect on the electrical and optical properties of the electrodes. The optimum thickness of the Ag metal thin film could be evaluated according to the optical transmittance, electrical conductivity, and figure of merit of the electrode. This study demonstrates that the α-IGZO/Ag/α-IGZO triple-layer transparent electrode can be fabricated with low sheet resistance (4.2 Ω/□) and high optical transmittance (88.1%) at room temperature without postannealing processing on the deposited thin films.

First principles examination of electronic structure and optical features of 4H-GaN1-xPx polytype alloys

NASA Astrophysics Data System (ADS)

Laref, A.; Hussain, Z.; Laref, S.; Yang, J. T.; Xiong, Y. C.; Luo, S. J.

2018-04-01

By using first-principles calculations, we compute the electronic band structures and typical aspects of the optical spectra of hexagonally structured GaN1-xPx alloys. Although a type III-V semiconductor, GaP commonly possesses a zinc-blende structure with an indirect band gap; as such, it may additionally form hexagonal polytypes under specific growth conditions. The electronic structures and optical properties are calculated by combining a non-nitride III-V semiconductor and a nitride III-V semiconductor, as GaP and GaN crystallizing in a 4H polytype, with the N composition ranging between x = 0-1. For all studied materials, the energy gap is found to be direct. The optical properties of the hexagonal materials may illustrate the strong polarization dependence owing to the crystalline anisotropy. This investigation for GaN1-xPx alloys is anticipated to supply paramount information for applications in the visible/ultraviolet spectral regions. At a specific concentration, x, these alloys would be exclusively appealing candidates for solar-cell applications.

Ab initio study of structural, electronic, optical, and vibrational properties of Zn x S y ( x + y = 2 to 5) nanoclusters

NASA Astrophysics Data System (ADS)

Yadav, P. S.; Pandey, D. K.; Agrawal, S.; Agrawal, B. K.

2010-03-01

An ab initio study of the stability, structural, electronic. and optical properties has been performed for 46 zinc sulfide nanoclusters Zn x S y ( x + y = n = 2 to 5). Five out of them are seen to be unstable as their vibrational frequencies are found to be imaginary. A B3LYP-DFT/6-311G(3df) method is employed to optimize the geometries and a TDDFT method is used for the study of the optical properties. The binding energies (BE), HOMO-LUMO gaps and the bond lengths have been obtained for all the clusters. For the ZnS2, ZnS3, and ZnS4 nanoclusters, our stable structures are seen to be different from those obtained earlier by using the effective core potentials. We have also considered the zero point energy (ZPE) corrections ignored by the earlier workers. For a fixed value of n, we designate the most stable structure the one, which has maximum final binding energy per atom. The adiabatic and vertical ionization potentials (IP) and electron affinities (EA), charges on the atoms, dipole moments, optical properties, vibrational frequencies, infrared intensities, relative infrared intensities, and Raman scattering activities have been investigated for the most stable structures. The nanoclusters containing large number of S atoms for each n is found to be most stable. The HOMO-LUMO gap decreases from n = 2-3 and then increases above n = 3. The IP and EA both fluctuate with the cluster size n. The optical absorption is quite weak in visible region but strong in the ultraviolet region in most of the nanoclusters except a few. The optical absorption spectrum or electron energy loss spectrum (EELS) is unique for every nanocluster and may be used to characterize a specific nanocluster. The growth of most stable nanoclusters may be possible in the experiments.

Optical property degradation of anodic coatings in the Space Station low earth orbit

NASA Technical Reports Server (NTRS)

David, Kaia E.; Babel, Hank W.

1992-01-01

The anodic coatings and optical properties to be used for passive thermal control of the SSF are studied. Particular attention is given to the beginning-of-life optical properties for aluminum alloys suitable for structural and radiator applications, the statistical variation in the beginning-of-life properties, and estimates of the end-of-life properties of the alloys based on ultraviolet radiation testing and flight test results. It is concluded that anodic coatings can be used for thermal control of long life, low earth orbit spacecraft. Some use restrictions are defined for specific cases. Anodic coatings have been selected as baseline thermal control coating for large portions of the SSF.

Structural and optical properties of Bi2O3-B2O3-CdO-Na2O glass system for gamma ray shielding applications

NASA Astrophysics Data System (ADS)

Dogra, Mridula; Singh, K. J.; Kaur, Kulwinder

2018-05-01

Quaternary system of the composition (0.15+x) Bi2O3-(0.55-x) B2O3-0.15CdO-0.15Na2O (where x=0, 0.1, 0.3 and 0.5 mole fraction) has been synthesized using melt-quenching technique. Gamma ray shielding properties are measured in terms of mass attenuation coefficient and half value layer at photon energies 662, 1173 and 1332 keV. These parameters are compared with standard nuclear radiation shielding `barite and ferrite' concretes. The results reflect better radiation shielding properties as compared to barite and ferrite concretes. Effective atomic number is calculated at photon energies 662 and 1173 keV. Density, molar volume and XRD studies are analyzed to know physical and structural properties of the glass system. Optical band gap, refractive index and molar refraction are calculated from UV-Visible measurements. Decrease in optical band gap and increase in molar refraction have been observed indicating the increase of non-bridging oxygens in the structure.

Structural and optoelectronic properties of P3HT-graphene composites prepared by in situ oxidative polymerization

NASA Astrophysics Data System (ADS)

Saini, Viney; Abdulrazzaq, Omar; Bourdo, Shawn; Dervishi, Enkeleda; Petre, Anca; Bairi, Venu Gopal; Mustafa, Thikra; Schnackenberg, Laura; Viswanathan, Tito; Biris, Alexandru S.

2012-09-01

Poly(3-hexylthiophene) (P3HT)-graphene nanocomposites were synthesized via in situ oxidative polymerization of 3-hexylthiophene monomer in the presence of graphene. The main thrust was to investigate the structural and optoelectronic properties of P3HT-graphene nanocomposites with various graphene concentrations. NMR spectroscopy was used to determine the regioregularity of the polymer composites, whereas Fourier transform infrared spectroscopy and differential scanning calorimetry were used to study their structural and thermal properties. Moreover, cyclic voltammetry was employed to evaluate the HOMO levels of the nanocomposites, while optical spectrophotometry (UV-Vis-NIR) was utilized to determine the optical bandgap of the composites. The information from the aforementioned techniques was used to estimate the HOMO-LUMO energy levels. The results revealed changes in the optical bandgap of P3HT with increasing graphene content. Furthermore, an extensive study aiming at the effect of graphene content on the optical constants of P3HT was conducted using ellipsometry. Photoluminescence analysis of the samples showed no quenching effect of photoluminescence emission with increasing graphene content. Our studies indicate that the inclusion of graphene impacts the optoelectronic properties of P3HT, which can further be used for advanced applications, such as organic solar cells, organic light emitting diodes, organic field-effect transistors, and polymer batteries.

Tuning of electronic band gaps and optoelectronic properties of binary strontium chalcogenides by means of doping of magnesium atom(s)- a first principles based theoretical initiative with mBJ, B3LYP and WC-GGA functionals

NASA Astrophysics Data System (ADS)

Debnath, Bimal; Sarkar, Utpal; Debbarma, Manish; Bhattacharjee, Rahul; Chattopadhyaya, Surya

2018-02-01

First principle based theoretical initiative is taken to tune the optoelectronic properties of binary strontium chalcogenide semiconductors by doping magnesium atom(s) into their rock-salt unit cells at specific concentrations x = 0.0, 0.25, 0.50, 0.75 and 1.0 and such tuning is established by studying structural, electronic and optical properties of designed binary compounds and ternary alloys employing WC-GGA, B3LYP and mBJ exchange-correlation functionals. Band structure of each compound is constructed and respective band gaps under all the potential schemes are measured. The band gap bowing and its microscopic origin are calculated using quadratic fit and Zunger's approach, respectively. The atomic and orbital origins of electronic states in the band structure of any compound are explored from its density of states. The nature of chemical bonds between the constituent atoms in each compound is explored from the valence electron density contour plots. Optical properties of any specimen are explored from the computed spectra of its dielectric function, refractive index, extinction coefficient, normal incidence reflectivity, optical conductivity optical absorption and energy loss function. Several calculated results are compared with available experimental and earlier theoretical data.

Electro-Optical Properties of Hydrogenated Si-Doped CdO

NASA Astrophysics Data System (ADS)

Dakhel, A. A.

2018-01-01

The optoelectronic properties of CdO films could be controlled and improved for transparent conducting (TC) purposes by means of doping. In the present work, several sets of CdO thin films hydrogenated and doped with different amounts of silicon were prepared on glass substrates by a thermal deposition technique in order to improve their TC properties. The x-ray diffraction method was used to study the crystal structural variations in CdO films as a consequence of Si(H) doping. Optical properties were studied by means of optical absorption and reflection spectroscopy. The observed blue-shifting in the optical bandgap by Si(H) doping was attributed to the Moss-Burstein effect with reduced structural bandgap by point defects created during the process of doping. The mechanism of the hydrogenation process was explained by the dissociation of hydrogen molecules into atoms/ions, which in turn interacted with structural oxygen ions leading to the creation of oxygen vacancies. The creation of oxygen vacancies caused increases in electron concentration ( N el) and electrical conductivity ( σ). The results showed that Si(H) doping of host CdO films significantly increased their conductivity, mobility, and carrier concentration by ˜ 69, 5.6, and 12.3 times, respectively. The results confirm that Si(H) doping is effective for using CdO films in transparent conducting oxide applications.

Nonlinear graphene plasmonics

PubMed Central

2017-01-01

The rapid development of graphene has opened up exciting new fields in graphene plasmonics and nonlinear optics. Graphene's unique two-dimensional band structure provides extraordinary linear and nonlinear optical properties, which have led to extreme optical confinement in graphene plasmonics and ultrahigh nonlinear optical coefficients, respectively. The synergy between graphene's linear and nonlinear optical properties gave rise to nonlinear graphene plasmonics, which greatly augments graphene-based nonlinear device performance beyond a billion-fold. This nascent field of research will eventually find far-reaching revolutionary technological applications that require device miniaturization, low power consumption and a broad range of operating wavelengths approaching the far-infrared, such as optical computing, medical instrumentation and security applications. PMID:29118665

Nonlinear graphene plasmonics

NASA Astrophysics Data System (ADS)

Ooi, Kelvin J. A.; Tan, Dawn T. H.

2017-10-01

The rapid development of graphene has opened up exciting new fields in graphene plasmonics and nonlinear optics. Graphene's unique two-dimensional band structure provides extraordinary linear and nonlinear optical properties, which have led to extreme optical confinement in graphene plasmonics and ultrahigh nonlinear optical coefficients, respectively. The synergy between graphene's linear and nonlinear optical properties gave rise to nonlinear graphene plasmonics, which greatly augments graphene-based nonlinear device performance beyond a billion-fold. This nascent field of research will eventually find far-reaching revolutionary technological applications that require device miniaturization, low power consumption and a broad range of operating wavelengths approaching the far-infrared, such as optical computing, medical instrumentation and security applications.

LIDAR Measurements of the Vertical Distribution of Aerosol Optical and Physical Properties over Central Asia

EPA Science Inventory

The vertical structure of aerosol optical and physical properties was measured by Lidar in Eastern Kyrgyzstan, Central Asia, from June 2008 to May 2009. Lidar measurements were supplemented with surface-based measurements of PM_2.5 and PM₁₀ mass and chemical ...

Optical and structural properties of carbon dots/TiO2 nanostructures prepared via DC arc discharge in liquid

NASA Astrophysics Data System (ADS)

Biazar, Nooshin; Poursalehi, Reza; Delavari, Hamid

2018-01-01

Synthesis and development of visible active catalysts is an important issue in photocatalytic applications of nanomaterials. TiO2 nanostructures coupled with carbon dots demonstrate a considerable photocatalytic activity in visible wavelengths. Extending optical absorption of a wide band gap semiconductor such as TiO2 with carbon dots is the origin of the visible activity of carbon dots modified semiconductor nanostructures. In addition, carbon dots exhibit high photostability, appropriate electron transport and chemical stability without considerable toxicity or environmental footprints. In this study, optical and structural properties of carbon dots/TiO2 nanostructures prepared via (direct current) DC arc discharge in liquid were investigated. Crystal structure, morphology and optical properties of the samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy respectively. SEM images show formation of spherical nanoparticles with an average size of 27 nm. In comparison with pristine TiO2, optical transmission spectrum of carbon dots/TiO2 nanostructures demonstrates an absorption edge at longer wavelengths as well a high optical absorption in visible wavelengths which is significant for visible activity of nanostructures as a photocatalyst. Finally, these results can provide a flexible and versatile pathway for synthesis of carbon dots/oxide semiconductor nanostructures with an appropriate activity under visible light.

Properties of the exotic metastable ST12 germanium allotrope

PubMed Central

Zhao, Zhisheng; Zhang, Haidong; Kim, Duck Young; Hu, Wentao; Bullock, Emma S.; Strobel, Timothy A.

2017-01-01

The optical and electronic properties of semiconducting materials are of great importance to a vast range of contemporary technologies. Diamond-cubic germanium is a well-known semiconductor, although other ‘exotic' forms may possess distinct properties. In particular, there is currently no consensus for the band gap and electronic structure of ST12-Ge (tP12, P43212) due to experimental limitations in sample preparation and varying theoretical predictions. Here we report clear experimental and theoretical evidence for the intrinsic properties of ST12-Ge, including the first optical measurements on bulk samples. Phase-pure bulk samples of ST12-Ge were synthesized, and the structure and purity were verified using powder X-ray diffraction, transmission electron microscopy, Raman and wavelength/energy dispersive X-ray spectroscopy. Optical measurements indicate that ST12-Ge is a semiconductor with an indirect band gap of 0.59 eV and a direct optical transition at 0.74 eV, which is in good agreement with electrical transport measurements and our first-principles calculations. PMID:28045027

Properties of the exotic metastable ST12 germanium allotrope

DOE PAGES

Zhao, Zhisheng; Zhang, Haidong; Kim, Duck Young; ...

2017-01-03

The optical and electronic properties of semiconducting materials are of great importance to a vast range of contemporary technologies. Diamond-cubic germanium is a well-known semiconductor, although other ‘exotic’ forms may possess distinct properties. In particular, there is currently no consensus for the band gap and electronic structure of ST12-Ge (tP12, P4 32 12) due to experimental limitations in sample preparation and varying theoretical predictions. Here we report clear experimental and theoretical evidence for the intrinsic properties of ST12-Ge, including the first optical measurements on bulk samples. Phase-pure bulk samples of ST12-Ge were synthesized, and the structure and purity were verifiedmore » using powder X-ray diffraction, transmission electron microscopy, Raman and wavelength/energy dispersive X-ray spectroscopy. Lastly, optical measurements indicate that ST12-Ge is a semiconductor with an indirect band gap of 0.59 eV and a direct optical transition at 0.74 eV, which is in good agreement with electrical transport measurements and our first-principles calculations.« less

Mechanical and optical characterization of tungsten oxynitride (W-O-N) nano-coatings

NASA Astrophysics Data System (ADS)

Nunez, Oscar Roberto

Aation and cation doping of transition metal oxides has recently gained attention as a viable option to design materials for application in solar energy conversion, photo-catalysis, transparent electrodes, photo-electrochemical cells, electrochromics and flat panel displays in optoelectronics. Specifically, nitrogen doped tungsten oxide (WO3) has gained much attention for its ability to facilitate optical property tuning while also demonstrating enhanced photo-catalytic and photochemical properties. The effect of nitrogen chemistry and mechanics on the optical and mechanical properties of tungsten oxynitride (W-O-N) nano-coatings is studied in detail in this work. The W-O-N coatings were deposited by direct current (DC) sputtering to a thickness of ˜100 nm and the structural, compositional, optical and mechanical properties were characterized in order to gain a deeper understanding of the effects of nitrogen incorporation and chemical composition. All the W-O-N coatings fabricated under variable nitrogen gas flow rate were amorphous. X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS) measurements revealed that nitrogen incorporation is effective only for a nitrogen gas flow rates ?9 sccm. Optical characterization using ultraviolet-visible-near infrared (UV-VIS-NIR) spectroscopy and spectroscopic ellipsometry (SE) indicate that the nitrogen incorporation induced effects on the optical parameters is significant. The band gap (Eg) values decreased from ˜2.99 eV to ˜1.89 eV indicating a transition from insulating WO3 to metallic-like W-N phase. Nano-mechanical characterization using indentation revealed a corresponding change in mechanical properties; maximum values of 4.46 GPa and 98.5 GPa were noted for hardness and Young?s modulus, respectively. The results demonstrate a clear relationship between the mechanical, physical and optical properties of amorphous W-O-N nano-coatings. The correlation presented in this thesis could provide a road-map to optimize and produce W-O-N nano-coatings with desired optical and mechanical properties for a given technological application in the field where structure, mechanical and optical properties are important.

Dispersion properties of plasma cladded annular optical fiber

NASA Astrophysics Data System (ADS)

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.

Processing and property evaluation of tungsten-based mixed oxides for photovoltaics and optoelectronics

NASA Astrophysics Data System (ADS)

Vargas, Mirella

Tungsten Oxide (WO3) films and low-dimensional structures have proven to be promising candidates in the fields of photonics and electronics. WO3 is a well-established n-type semiconductor characterized by unique electrochromic behavior, an ideal optical band gap that permits transparency over a wide spectral range, and high chemical integrity. The plethora of diverse properties endow WO3 to be highly effective in applications related to electrochromism, gas sensing, and deriving economical energy. Compared to the bulk films, a materials system involving WO3 and a related species (elements or metal oxides) offer the opportunity to tailor the electrochromic response, and an overall enhancement of the physio-chemical and optical properties. In the present case, WO3 and TiO2 composite films have been fabricated by reactive magnetron sputtering employing W/Ti alloy targets, and individual W and Ti targets for co-sputtering. Composite WO3-TiO2 films were fabricated with variable chemical composition and the effect of variable bulk chemistry on film structure, surface/interface chemistry and chemical valence state of the W and Ti cations was investigated in detail. The process-property relationships between composition and physical properties for the films deposited by using W/Ti alloy targets of variable Ti content are associated with decreases in the deposition rate of the WO3-TiO2 films due to the lower sputter yield of the strongly bonded TiO2 formed on the target surface. Additionally, for the co-sputtered films using variable tungsten power, the optical properties demonstrate unique optical modulation. The changes associated with the physical color of the films demonstrate the potential to tailor the optical behavior for the design and fabrication of multilayer photovoltaic and catalytic devices. The process-structure-property correlation derived in this work will provide a road-map to optimize and produce W-Ti-O thin films with desired properties for a given technological application.

Effect of the structure and mechanical properties of the near-surface layer of lithium niobate single crystals on the manufacture of integrated optic circuits

NASA Astrophysics Data System (ADS)

Sosunov, A. V.; Ponomarev, R. S.; Yur'ev, V. A.; Volyntsev, A. B.

2017-01-01

This paper shows that the near-surface layer of a lithium niobate single layer 15 μm in depth is essentially different from the rest of the volume of the material from the standpoint of composition, structure, and mechanical properties. The pointed out differences are due to the effect of cutting, polishing, and smoothing of the lithium niobate plates, which increase the density of point defects and dislocations. The increasing density of the structural defects leads to uncontrollable changes in the conditions of the formations of waveguides and the drifting of characteristics of integrated optical circuits. The results obtained are very important for the manufacture of lithium niobate based integrated optical circuits.

Pressure-Induced Structural Evolution and Band Gap Shifts of Organometal Halide Perovskite-Based Methylammonium Lead Chloride.

PubMed

Wang, Lingrui; Wang, Kai; Xiao, Guanjun; Zeng, Qiaoshi; Zou, Bo

2016-12-15

Organometal halide perovskites are promising materials for optoelectronic devices. Further development of these devices requires a deep understanding of their fundamental structure-property relationships. The effect of pressure on the structural evolution and band gap shifts of methylammonium lead chloride (MAPbCl 3 ) was investigated systematically. Synchrotron X-ray diffraction and Raman experiments provided structural information on the shrinkage, tilting distortion, and amorphization of the primitive cubic unit cell. In situ high pressure optical absorption and photoluminescence spectra manifested that the band gap of MAPbCl 3 could be fine-tuned to the ultraviolet region by pressure. The optical changes are correlated with pressure-induced structural evolution of MAPbCl 3 , as evidenced by band gap shifts. Comparisons between Pb-hybrid perovskites and inorganic octahedra provided insights on the effects of halogens on pressure-induced transition sequences of these compounds. Our results improve the understanding of the structural and optical properties of organometal halide perovskites.

Spatially oriented plasmonic ‘nanograter’ structures

PubMed Central

Liu, Zhe; Cui, Ajuan; Gong, Zhijie; Li, Hongqiang; Xia, Xiaoxiang; Shen, Tiehan H.; Li, Junjie; Yang, Haifang; Li, Wuxia; Gu, Changzhi

2016-01-01

One of the key motivations in producing 3D structures has always been the realization of metamaterials with effective constituent properties that can be tuned in all propagation directions at various frequencies. Here, we report the investigation of spatially oriented “Nanograter” structures with orientation-dependent responses over a wide spectrum by focused-ion-beam based patterning and folding of thin film nanostructures. Au nano units of different shapes, standing along specifically designated orientations, were fabricated. Experimental measurements and simulation results show that such structures offer an additional degree of freedom for adjusting optical properties with the angle of inclination, in additional to the size of the structures. The response frequency can be varied in a wide range (8 μm–14 μm) by the spatial orientation (0°–180°) of the structures, transforming the response from magnetic into electric coupling. This may open up prospects for the fabrication of 3D nanostructures as optical interconnects, focusing elements and logic elements, moving toward the realization of 3D optical circuits. PMID:27357610

Structural and optical studies of hydrothermally synthesized MoS{sub 2} nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chacko, Levna; Swetha, A. K.; Aneesh, P. M., E-mail: aneeshpm@cukerala.ac.in

2016-05-06

Transition-metal dichalcogenides like molybdenum disulphide have intrigued intensive interest as two-dimensional (2D) materials beyond extensively studied graphene due to their unique electronic and optical properties. Here we report the hydrothermal synthesis of MoS{sub 2} nanostructures without the addition of any surfactants. The structural and optical properties of the synthesized samples were characterized by various techniques, including X-ray diffraction (XRD), UV-Vis absorption, photoluminescence (PL), and Raman analysis. XRD and Raman spectroscopic studies confirm the formation of hexagonal phase and well ordered stacking of S-Mo-S layers. The increased lattice parameters of MoS{sub 2} samples are due to the stress or strain inducedmore » bending and folding of the layers. The synthesized MoS{sub 2} nanostructures shows a large optical absorption in 300-700 nm region and strong luminescence at 640 nm. In addition, the optical results demonstrates the quantum confinement in layered d-electron material MoS{sub 2} that can lead to engineer its various properties for electronic and optoelectronic applications.« less

Optical and morphological study of disorder in opals

NASA Astrophysics Data System (ADS)

Palacios-Lidón, E.; Juárez, B. H.; Castillo-Martínez, E.; López, C.

2005-03-01

An optical and morphological study has been carried out to understand the role of intrinsic defects in the optical properties of opal-based photonic crystals. By doping poly(methylmethacrylate) (PMMA) thin-film opals with larger polystyrene (PS) spheres, structural disorder has being generated perturbing the PMMA matrix periodicity. It is shown that this disorder dramatically affects the optical response of the system worsening its photonic properties. It has been found that the effect of doping is highly dependent not only on the concentration but also on the relative size of the dopant with reference to the matrix. Through a detailed scanning electron microscopy inspection, the sort of structural defects involved, derived from the different particle size used, has been characterized. A direct relationship between the observed optical response with the different perturbations generated in the lattice has been found. In addition, from this study it can be concluded that it is possible to grow high quality alloyed photonic crystals, exhibiting intermediate photonic properties between pure PMMA and pure PS opals by simple sphere size matching and variation of the relative concentration of both components.

Electronic and Optical Properties of Borophene, a Two-dimensional Transparent Metal.

NASA Astrophysics Data System (ADS)

Adamska, Lyudmyla; Sadasivam, Sridhar; Darancet, Pierre; Sharifzadeh, Sahar

Borophene is a recently synthesized metallic sheet that displays many similarities to graphene and has been predicted to be complimentary to graphene as a high density of states, optically transparent 2D conductor. The atomic arrangement of boron in the monolayer strongly depends on the growth substrate and significantly alters the optoelectronic properties. Here, we report a first-principles density functional theory and many-body perturbation theory study aimed at understanding the optoelectronic properties of two likely allotropes of monolayer boron that are consistent with experimental scanning tunneling microscopy images. We predict that despite both systems are metallic, the two allotropes have substantially different bandstructure and optical properties, with one structure being transparent up to 3 eV and the second weakly absorbing in the UV/Vis region. We demonstrate that this strong structure-dependence of optoelectronic properties is present with the application of strain. Lastly, we discuss the strength of electron-phonon and electron-hole interactions within these materials. Overall, we determine that precise control of the growth conditions in necessary for controlled optical properties. This research used resources of the Argonne Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC02-06CH11357, and the Texas Advanced Computing Center (TACC) at The University of Texas at Austin.

Electro Optical Properties of Copolymer Blends: Lasing, Electroluminescence and Photophysics

DTIC Science & Technology

2006-04-15

conjugated main chain structures with high photoluminescent and electroluminescent quantum yields. The structures incorporated fluorene containing moieties...The systems studied focused on novel conjugated main chain structures with high photoluminescent and electroluminescent quantum yields. The structures...the quantum efficient fluorine group. The properties of segmented copolymers that incorporate fluorenes were compared to the homo-PPV type systems

Structural and optical properties of CdSe nanosheets

NASA Astrophysics Data System (ADS)

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.

A simple growth method for Nb 2O 5 films and their optical properties

DOE PAGES

Dash, J. K.; Chen, L.; Topka, Michael R.; ...

2015-04-13

A simple method for the synthesis of Nb₂O₅ films of thicknesses ranging from tens to several hundreds of nanometers on amorphous silicon dioxide or quartz substrates is presented. Nb₂O₅ films were formed by annealing the sputter deposited Nb films under an Ar flow and without oxygen plasma in a quartz tube within a furnace at 850 °C. The structural, compositional, optical, and vibrational properties were characterized by grazing incidence X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet visible spectroscopy, and Raman scattering. Each of the Nb₂O₅ films is polycrystalline with an orthorhombic crystal structure. We observed vibrational modes includingmore » longitudinal optical, transverse optical, and triply degenerate modes, and measured the indirect optical band gap to be ~3.65 eV. The transmittance spectrum of the ~20 nm thick Nb₂O₅ film shows over 90% transmittance below the band gap energy in the visible wavelength range and decreases to less than 20% in the ultraviolet regime. As a result, the optical properties of the films in the UV-vis range show potential applications as UV detectors.« less

Magneto-transport and magneto-optical studies on SnO2 transparent semiconducting thin films alloyed with Mn over a wide range of concentration

NASA Astrophysics Data System (ADS)

Bagheri Mohagheghi, M. M.; Tabatabai Yazdi, Sh.; Mousavi, M.

2018-03-01

In this work, Mn-alloyed tin oxide transparent thin films with different Mn concentrations up to 60 at% were prepared via the spray pyrolysis method, and their structural, magneto-optical, and magneto-transport properties were studied. The results show that all the deposited films are polycrystalline with the tetragonal rutile structure. The unit cell volume of Sn1- x Mn x O2 films was found to be minimum at the Mn concentration of x = 0.15 indicating to two different mechanisms for Mn addition in the crystal lattice of tin oxide. For the films with Mn concentrations less than 15%, substitutional doping is the working mechanism, while for more Mn concentrations, interstitial one is predominant. A critical Mn concentration about that observed for the structural properties of the films (i.e., x = 0.15) was revealed for their magnetoresistance and magneto-optical properties, as well. This suggests a correlation between the structural and magnetic behaviors of the deposited SnO2:Mn films.

Impact of neutron irradiation on the structural and optical properties of PVP/gelatin blends doped with dysprosium (III) chloride

NASA Astrophysics Data System (ADS)

Basha, Ahmad Fouad; Basha, Mohammad Ahmad-Fouad

2017-12-01

Polymer composites of a system of Polyvinylpyrrolidone (PVP)/gelatin/DyCl3.6H2O were prepared in three groups that have different concentrations of PVP/gelatin contents to study the effect of neutron irradiation on their structural and optical properties. Results showed that the interaction of neutrons led to various complex phenomena, mainly bond breaking, main chain scission and intermolecular cross-linking. These processes introduced defects inside the material that were responsible for the changes in their optical and structural properties. All the calculated parameters were found to be dependent on the irradiation fluence in a uniform manner that makes these materials excellent candidates in the applications of dosimetry and radiology. Moreover, the sensitivity of the three groups of composites to the irradiation doses was found to be different. The variation in the structure of the composite group that contains the least PVP content was found to be less significant; hence, these materials were more stable against high doses that make them suitable for high radiation dose applications.

First-principle calculations of structural, electronic, optical, elastic and thermal properties of MgXAs2 (X=Si, Ge) compounds

NASA Astrophysics Data System (ADS)

Cheddadi, S.; Boubendira, K.; Meradji, H.; Ghemid, S.; Hassan, F. El Haj; Lakel, S.; Khenata, R.

2017-12-01

First-principle calculations on the structural, electronic, optical, elastic and thermal properties of the chalcopyrite MgXAs2 (X=Si, Ge) have been performed within the density functional theory (DFT) using the full-potential linearized augmented plane wave (FP-LAPW) method. The obtained equilibrium structural parameters are in good agreement with the available experimental data and theoretical results. The calculated band structures reveal a direct energy band gap for the interested compounds. The predicted band gaps using the modified Becke-Johnson (mBJ) exchange approximation are in fairly good agreement with the experimental data. The optical constants such as the dielectric function, refractive index, and the extinction coefficient are calculated and analysed. The independent elastic parameters namely, C_{11}, C_{12}, C_{13}, C_{33}, C_{44} and C_{66 } are evaluated. The effects of temperature and pressure on some macroscopic properties of MgSiAs2 and MgGeAs2 are predicted using the quasiharmonic Debye model in which the lattice vibrations are taken into account.

Optical properties of boron-group (V) hexagonal nanowires: DFT investigation

NASA Astrophysics Data System (ADS)

Santhibhushan, B.; Soni, Mahesh; Srivastava, Anurag

2017-07-01

The paper presents structural, electronic and optical properties of boron-group V hexagonal nanowires (h-NW) within the framework of density functional theory. The h-NW of boron-group V compounds with an analogous diameter of 12 Å have been designed in (1 1 1) plane. Stability analysis performed through formation energies reveal that, the stability of these structures decreases with increasing atomic number of the group V element. The band nature predicts that these nanowires are good electrical conductors. Optical behaviour of the nanowires has been analysed through absorption coefficient, reflectivity, refractive index, optical conductivity and electron energy loss spectrum (EELS), that are computed from the frequency-dependent complex dielectric function. The analysis reveals high reactivity of BP and BAs h-NWs to the incident light especially in the IR and visible ranges, and the optical transparency of BN h-NW in the visible and UV ranges.

Third order nonlinear optical properties of Mn doped CeO2 nanostructures

NASA Astrophysics Data System (ADS)

Mani Rahulan, K.; Angeline Little Flower, N.; Annie Sujatha, R.; Mohana Priya, P.; Gopalakrishnan, C.

2018-05-01

Mn doped CeO2 nanoparticles with different ratios of Mn were synthesized by hydrothermal method and their structural properties were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). XRD patterns revealed that the peaks are highly crystalline structure with no segregation of Mn. The surface morphology from SEM reveals that particle size decreases with increase in Mn concentration. Nonlinear optical studies of the samples were measured by single-beam open aperture Z-scan technique using 5 ns laser pulses at 532 nm. The measured optical nonlinearity of all the samples exhibit typical third order nonlinear optical behavior including two-photon absorption (2 PA) and reverse saturable absorption (RSA). The experimental results show that the presence of RSA in these nanoparticles makes them a promising material for the fabrication of optical limiting devices. .

FINAL REPORT: Scalable Methods for Electronic Excitations and Optical Responses of Nanostructures: Mathematics to Algorithms to Observables

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chelikowsky, James R.

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 accessedmore » 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.« less

Electronic structure and optical property of boron doped semiconducting graphene nanoribbons

NASA Astrophysics Data System (ADS)

Chen, Aqing; Shao, Qingyi; Wang, Li; Deng, Feng

2011-08-01

We present a system study on the electronic structure and optical property of boron doped semiconducting graphene nanoribbons using the density functional theory. Energy band structure, density of states, deformation density, Mulliken popular and optical spectra are considered to show the special electronic structure of boron doped semiconducting graphene nanoribbons. The C-B bond form is discussed in detail. From our analysis it is concluded that the Fermi energy of boron doped semiconducting graphene nanoribbons gets lower than that of intrinsic semiconducting graphene nanoribbons. Our results also show that the boron doped semiconducting graphene nanoribbons behave as p-type semiconducting and that the absorption coefficient of boron doped armchair graphene nanoribbons is generally enhanced between 2.0 eV and 3.3 eV. Therefore, our results have a great significance in developing nano-material for fabricating the nano-photovoltaic devices.

Study of structural, electronic and optical properties of tungsten doped bismuth oxychloride by DFT calculations.

PubMed

Yang, Wenjuan; Wen, Yanwei; Chen, Rong; Zeng, Dawen; Shan, Bin

2014-10-21

First-principle calculations have been carried out to investigate structural stabilities, electronic structures and optical properties of tungsten doped bismuth oxychloride (BiOCl). The structures of substitutional and interstitial tungsten, and in the form of WO6-ligand-doped BiOCl are examined. The substitutional and interstitial tungsten doping leads to discrete midgap states within the forbidden band gap, which has an adverse effect on the photocatalytic properties. On the other hand, the WO6-ligand-doped BiOCl structure induces a continuum of hybridized states in the forbidden gap, which favors transport of electrons and holes and could result in enhancement of visible light activity. In addition, the band gap of WO6-BiOCl decreases by 0.25 eV with valence band maximum (VBM) shifting upwards compared to that of pure BiOCl. By calculating optical absorption spectra of pure BiOCl and WO6-ligand-doped BiOCl structure, it is found that the absorption peak of the WO6-ligand-doped BiOCl structure has a red shift towards visible light compared with that of pure BiOCl, which agrees well with experimental observations. These results reveal the tungsten doped BiOCl system as a promising material in photocatalytic decomposition of organics and water splitting under sunlight irradiation.

Investigation of microstructural and optical properties of La0.8Ca0.2FeO3 nanostructure synthesized via gel combustion method

NASA Astrophysics Data System (ADS)

Naseem, Swaleha; Ali, S. Asad; Khan, Wasi; Khan, Shakeel

2018-05-01

Ca substituted LaFeO3 orthoferrite nanostructure perovskite has been synthesized by gel combustion method using citric acid as a fuel. The structural and optical properties were investigated by various tools. The structural analysis through Rietveld refinement of the XRD data revealed single phase of orthorhombic structure in R-3c space group of the sample without presence of any other impurity phase. Scanning electron microscopy (SEM) image exhibits non-uniform distribution of the nanoparticles in agglomerated form. The purity of the sample and stoichiometric ratio of the elements were established through energy dispersive x-ray spectroscopy (EDS). FTIR spectroscopy measurement predicts the presence of various band relation of the chemical species of Ca with LaFeO3. Optical properties were explored through UV-visible absorption spectroscopy that showed absorption edge at 347 nm and energy band gap was estimated as 3.47eV using Tauc's relation.

Triple modifier effect on physical, optical and structural properties of boro tellurite zinc lithium glasses

NASA Astrophysics Data System (ADS)

Naresh, P.; Srinivasu, D.; Narsimlu, N.; Ch. Srinivas, Kavitha, B.; Deshpandhe, Uday; Kumar, K. Siva

2018-05-01

To investigate physical, optical and structural properties of glass samples of the Quaternary system (60-x)B2O3-xTeO2-10ZnO-30Li2O with x=0,5,10,15, and 20 mol% were prepared by conventional melt quenching technique. XRD confirmed the amorphous nature of all samples. Physical parameters like density, molar volume, Oxygen packing density and etc. calculated. Density of glass samples increased with the increase of TeO2 concentration due to the replacement of lighter B2O3 with heavier TeO2. Optical properties has studied with the help of UV-Visible spectra. Cut off wavelength is increases whereas Eopt and Urbache energies is decreased except intermediate mole fraction of TeO2 at which the triple modifier effect can be observed. Fourier Transform Infrared spectroscopy reveals that the network consists of TeO3 and TeO6 structural units along with BO3 and BO4 units.

Investigations on the structural, morphological, optical and electrical properties of undoped and nanosized Zn-doped CdS thin films prepared by a simplified spray technique

NASA Astrophysics Data System (ADS)

Anbarasi, M.; Nagarethinam, V. S.; Balu, A. R.

2014-12-01

CdS and Zn-doped CdS (CdS:Zn) thin films have been deposited on glass substrates by spray pyrolysis technique using a perfume atomizer. The influence of Zn incorporation on the structural, morphological, optical and electrical properties of the films has been studied. All the films exhibit hexagonal phase with (0 0 2) as preferential orientation. A shift of the (0 0 2) diffraction peak towards higher diffraction angle is observed with increased Zn doping. The optical studies confirmed that the transparency increases as Zn doping level increases and the film coated with 2 at.% Zn doping has the maximum transmittance of about 90 %. The sheet resistance (R sh ) decreases as the Zn-doping level increases and a minimum value of 1.113 × 103 Ω/sq is obtained for the film coated with 8 at.% Zn dopant. The CdS film coated with 8 at.% Zn dopant has the best structural, morphological and electrical properties.

Effect of substrate rotation speed and off-center deposition on the structural, optical, and electrical properties of AZO thin films fabricated by DC magnetron sputtering

NASA Astrophysics Data System (ADS)

Turkoglu, F.; Koseoglu, H.; Zeybek, S.; Ozdemir, M.; Aygun, G.; Ozyuzer, L.

2018-04-01

In this study, aluminum-doped zinc oxide (AZO) thin films were deposited by DC magnetron sputtering at room temperature. The distance between the substrate and target axis, and substrate rotation speed were varied to get high quality AZO thin films. The influences of these deposition parameters on the structural, optical, and electrical properties of the fabricated films were investigated by X-ray diffraction (XRD), Raman spectroscopy, spectrophotometry, and four-point probe techniques. The overall analysis revealed that both sample position and substrate rotation speed are effective in changing the optical, structural, and electrical properties of the AZO thin films. We further observed that stress in the films can be significantly reduced by off-center deposition and rotating the sample holder during the deposition. An average transmittance above 85% in the visible range and a resistivity of 2.02 × 10-3 Ω cm were obtained for the AZO films.

Revisiting polarimetry near the isotropic point of an optically active, non-enantiomorphous, molecular crystal.

PubMed

Martin, Alexander T; Tan, Melissa; Nichols, Shane M; Timothy, Emily; Kahr, Bart

2018-07-01

Accurate polarimetric measurements of the optical activity of crystals along low symmetry directions are facilitated by isotropic points, frequencies where dispersion curves of eigenrays cross and the linear birefringence disappears. We report here the optical properties and structure of achiral, uniaxial (point group D 2d ) potassium trihydrogen di-(cis-4-cyclohexene-1,2-dicarboxylate) dihydrate, whose isotropic point was previously detected (S. A. Kim, C. Grieswatch, H. Küppers, Zeit. Krist. 1993; 208:219-222) and exploited for a singular measurement of optical activity normal to the optic axis. The crystal structure associated with the aforementioned study was never published. We report it here, confirming the space group assignment I 4¯c2, along with the frequency dependence of the fundamental optical properties and the constitutive tensors by fitting optical dispersion relations to measured Mueller matrix spectra. k-Space maps of circular birefringence and of the Mueller matrix near the isotropic wavelength are measured and simulated. The signs of optical rotation are correlated with the absolute crystallographic directions. © 2018 Wiley Periodicals, Inc.

Progression in structural, magnetic and electrical properties of La-doped group IV elements

NASA Astrophysics Data System (ADS)

Deepapriya, S.; Annie Vinosha, P.; Rodney, John D.; Jerome Das, S.

2018-04-01

Progression of group IV elements such as zinc ferrite (ZnFe2O4), cobalt ferrite (CoFe2O4) was synthesized by doping lanthanum (La), via adopting a facile co-precipitation method. Doping hefty rare earth ion in spinel structure can amend to the physical properties of the lattice, which can be used in the enhancement of magnetic and electrical properties of the as-synthesized nanomaterial, it is vital to metamorphose and optimize its micro structural and magnetic features. The structural properties of the samples was analysed by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), Transmission electron microscopy (TEM) and UV-visible spectral analysis (UV-vis) reveals the optical property and optical band gap. The magnetic properties were evaluated using a vibrating sample magnetometer (VSM), the presence of functional group was confirmed by FTIR. XRD analyses elucidates that the synthesized samples zinc and cobalt had a spinel structure. From TEM analyses the morphology and diameter of the particle was observed. The substituted rare earth ions in Zinc ferrite inhibit the grain growth of the materials in an efficient manner compared with that of the Cobalt ferrite.

Effect of annealing on structure, morphology and optoelectronic properties of nanocrystalline CuO thin films

NASA Astrophysics Data System (ADS)

Jundale, D. M.; Pawar, S. G.; Patil, S. L.; Chougule, M. A.; Godse, P. R.; Patil, V. B.

2011-10-01

The nanocrystalline CuO thin films were prepared on glass substrates by the sol-gel method. The structural, morphological, electrical and optical properties of CuO thin films, submitted to an annealing treatment in the 400-700 °C ranges are studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Four Probe Technique and UV-visible spectroscopic. XRD measurements show that all the films are crystallized in the monoclinic phase and present a random orientation. Four prominent peaks, corresponding to the (110) phase (2θ≈32.70°), (002) phase (2θ≈35.70°), (111) phase (2θ≈38.76°) and (202) phase (2θ≈49.06°) appear on the diffractograms. The crystallite size increases with increasing annealing temperature. These modifications influence the microstructure, electrical and optical properties. The optical band gap energy decreases with increasing annealing temperature. These mean that the optical quality of CuO films is improved by annealing.

Study of lattice strain and optical properties of nanocrystalline SnO2

NASA Astrophysics Data System (ADS)

Ahmad, Naseem; Khan, Shakeel; Bhargava, Richa; Ansari, Mohd Mohsin Nizam

2018-05-01

Nanocrystalline SnO2 has been synthesized by co-precipitation method by using two solvents (water and ethylene glycol). The structure and surface morphology were investigated using XRD and scanning electron microscope (SEM). The optical properties were studied using diffused reflectance spectroscopy (DRS). From the XRD analysis, the prepared materials are found to be pure crystalline with tetragonal rutile structure. The lattice strain and crystallite size, were calculated using Williamson-Hall method, are found to be 0.00413 & 16.3 nm in water assisted SnO2 and 0.00495 & 35.6 nm for EG assisted SnO2. Study of surface morphology of the samples was carried out using SEM. It has been seen that the solvents which are used in synthesis can also alter the optical properties of the materials. The optical band gap of the water based SnO2 and EG based SnO2 are found to be 3.92eV and 3.86eV respectively.

Chemical bath deposited (CBD) CuO thin films on n-silicon substrate for electronic and optical applications: Impact of growth time

NASA Astrophysics Data System (ADS)

Sultana, Jenifar; Paul, Somdatta; Karmakar, Anupam; Yi, Ren; Dalapati, Goutam Kumar; Chattopadhyay, Sanatan

2017-10-01

Thin film of p-type cupric oxide (p-CuO) is grown on silicon (n-Si) substrate by using chemical bath deposition (CBD) technique and a precise control of thickness from 60 nm to 178 nm has been achieved. The structural properties and stoichiometric composition of the grown films are observed to depend significantly on the growth time. The chemical composition, optical properties, and structural quality are investigated in detail by employing XRD, ellipsometric measurements and SEM images. Also, the elemental composition and the oxidation states of Cu and O in the grown samples have been studied in detail by XPS measurements. Thin film of 110 nm thicknesses exhibited the best performance in terms of crystal quality, refractive index, dielectric constant, band-gap, and optical properties. The study suggests synthesis route for developing high quality CuO thin film using CBD method for electronic and optical applications.

Various physical properties of Mn_1-xFex alloy films

NASA Astrophysics Data System (ADS)

Kim, J. B.; Cho, K. H.; Nahm, T.-U.; Lee, Y. P.; Kim, K. W.; Kudryavtsev, Y. V.; Gontarz, R.; Szymanski, B.

2003-03-01

The structural dependences of the magneto-optical, the optical and the magnetic properties of Mn_1-xFex alloy films have been investigated. It was revealed that the EKE (equatorial Kerr effect) signal at 293 K for the Mn_1-xFex alloy films can be observed only for x > 0.50. All the EKE spectra have nearly the same spectral shape (Fe-like) and differ from each other only in the intensity. The observed experimental EKE spectra for the Fe-rich Mn_1-xFex alloy films can be nicely described by the simulated ones made in the framework of the effective medium approximation. The optical properties such as optical conductivity of all the investigated alloys can be separated into three groups which are related to the different crystalline structures of alloys: predominance of the α-Fe (0.8 < x < 0.97), the γ-Mn-Fe (0.2 < x < 0.6) and the α-Mn (0.02 < x < 0.23) phases, respectively.

Crystal growth, structural, optical, mechanical and thermal properties of a new nonlinear optical single crystal: L-Ornithine monohydrochloride.

PubMed

Balakrishnan, T; Ramamurthi, K

2009-03-01

Amino acid family crystals exhibit excellent nonlinear optical and electro optical properties. l-Ornithine monohydrochloride single crystal, belongs to the amino acid group, was grown by the slow evaporation solution growth technique at room temperature. The grown crystals were characterized by single crystal and powder X-ray diffraction analysis, Fourier transform infrared (FTIR) spectroscopy, TGA, DTA and DSC analyses. UV-vis-NIR spectrum shows excellent transmission in the UV, visible and NIR region (300-1600nm). The mechanical properties of grown crystals were studied using Vickers microhardness tester. Its second harmonic generation efficiency was tested using Nd:YAG laser and is 1.25 times that of KDP.

Nonlinear optical properties of metal alkanoate composites with hybrid core/shell nanoparticles

NASA Astrophysics Data System (ADS)

Rudenko, V.; Tolochko, A.; Zhulai, D.; Klimusheva, G.; Mirnaya, T.; Yaremchuk, G.; Asaula, V.

2018-02-01

New composites with hybrid CdSe/ZnS and Au/CdSe nanoparticles (NPs) were chemically synthesized in the thermotropic liquid crystalline phase (smectic A) of cadmium octanoate. Features of structure and nonlinear optical properties of glassy cadmium octanoate composites with hybrid core/shell NPs were studied using small-angle X-ray scattering method and Z-scan technique. Experimental optical setup (Z-scan) is based on a Nd: YAG laser, generating 9 ns pulses with a repetition rate of 0,5 Hz on a wavelength of 532 nm. The effects of the influence of hybrid NPs on the nonlinear optical properties of nanocomposites are considered in this study.

Ba 2TeO as an optoelectronic material: First-principles study

DOE PAGES

Sun, Jifeng; Shi, Hongliang; Du, Mao-Hua; ...

2015-05-21

The band structure, optical and defects properties of Ba 2TeO are systematically investigated using density functional theory with a view to understanding its potential as an optoelectronic or transparent conducting material. Ba 2TeO crystallizes with tetragonal structure (space group P4/nmm) and with a 2.93 eV optical band gap1. We find relatively modest band masses for both electrons and holes suggesting applications. Optical properties show a infrared-red absorption when doped. This could potentially be useful for combining wavelength filtering and transparent conducting functions. Furthermore, our defect calculations show that Ba 2TeO is intrinsically p-type conducting under Ba-poor condition. However, the spontaneousmore » formation of the donor defects may constrain the p-type transport properties and would need to be addressed to enable applications.« less

Photonic Resins: Designing Optical Appearance via Block Copolymer Self-Assembly

PubMed Central

2018-01-01

Despite a huge variety of methodologies having been proposed to produce photonic structures by self-assembly, the lack of an effective fabrication approach has hindered their practical uses. These approaches are typically limited by the poor control in both optical and mechanical properties. Here we report photonic thermosetting polymeric resins obtained through brush block copolymer (BBCP) self-assembly. We demonstrate that the control of the interplay between order and disorder in the obtained photonic structure offers a powerful tool box for designing the optical appearance of the polymer resins in terms of reflected wavelength and scattering properties. The obtained materials exhibit excellent mechanical properties with hardness up to 172 MPa and Young’s modulus over 2.9 GPa, indicating great potential for practical uses as photonic coatings on a variety of surfaces. PMID:29681653

Optical, electrical properties and structural characterization of ZnO:rGO based photodetector

NASA Astrophysics Data System (ADS)

Nath, Debarati; Mandal, S. K.; Deb, Debajit; Rakshit, J. K.; Dey, P.; Roy, J. N.

2018-04-01

Pure ZnO and ZnO:rGO composite films are prepared by sol-gel process and the effect of reduced graphene oxide(rGO) on structural, optical and electrical properties of the film are studied. UV-visspectrum shows that composite film exhibit similar optical absorbance property as pure ZnOfilm. Band gap of the film is changed from 3.32 to 3.21 eV by incorporation of rGO. From current-voltage curve it can be observed that photo current is increased significantly in composite film under red laser light illumination. This result suggests that conduction mechanism in composite film is dominated by rGO. Nyquist plot of both films show only one semicircle behavior in measured frequency range, which may be attributed to grain boundaries effects in the composite.

Structural, electrical, optical and magnetic properties of NiO/ZnO thin films

NASA Astrophysics Data System (ADS)

Sushmitha, V.; Maragatham, V.; Raj, P. Deepak; Sridharan, M.

2018-02-01

Nickel oxide/Zinc oxide (NiO/ZnO) thin films have been deposited onto thoroughly cleaned glass substrates by reactive direct current (DC) magnetron sputtering technique and subsequently annealed at 300 °C for 3 h in vacuum. The NiO/ZnO thin films were then studied for their structural, optical and electrical properties. X-ray diffraction (XRD) pattern of ZnO and NiO showed the diffraction planes corresponding to hexagonal and cubic phase respectively. The optical properties showed that with the increase in the deposition time of NiO the energy band gap varied between 3.1 to 3.24 eV. Hence, by changing the deposition time of NiO the tuning of band gap and conductivity were achieved. The magnetic studies revealed the diamagnetic nature of the NiO/ZnO thin films.

Composite Films Formed by Cellulose nanocrystals and Latex Nanoparticles: Optical, Structural, and Mechanical Properties

NASA Astrophysics Data System (ADS)

Vollick, Brandon McRae

This thesis describes the preparation of iridescent, birefringent, composite films composed of cellulose nanocrystals (CNCs), latex nanoparticles (NPs) and a NP crosslinker; hexanediamine (HDA). First, aqueous suspensions were prepared with varying quantities of CNCs, NPs and HDA before equilibrating for one week. The cholesteric (Ch) phase was then cast and dried into a film. The optical, structural and mechanical properties of the film was analyzed. Second, films with identical compositions of CNCs, NPs, and HDA were fabricated in three different ways to yield films of different morphology, (i) fast drying of an isotropic suspension, yielding an isotropic film, (ii) slow drying of an isotropic suspension, yielding a partially Ch films, (iii) slow drying of an equilibrated suspension, yielding a highly Ch film. The optical and mechanical properties of the films was analyzed.

Electronic and optical properties of Si and Ge nanocrystals: An ab initio study

NASA Astrophysics Data System (ADS)

Pulci, Olivia; Degoli, Elena; Iori, Federico; Marsili, Margherita; Palummo, Maurizia; Del Sole, Rodolfo; Ossicini, Stefano

2010-01-01

First-principles calculations within density functional theory and many-body perturbation theory have been carried out in order to investigate the structural, electronic and optical properties of undoped and doped silicon nanostructures. We consider Si nanoclusters co-doped with B and P. We find that the electronic band gap is reduced with respect to that of the undoped crystals, suggesting the possibility of impurity based engineering of electronic and optical properties of Si nanocrystals. Finally, motivated by recent suggestions concerning the chance of exploiting Ge dots for photovoltaic nanodevices, we present calculations of the electronic and optical properties of a Ge 35H 36 nanocrystal, and compare the results with those for the corresponding Si 35H 36 nanocrystals and the co-doped Si 33BPH 36.

Improving diffuse optical tomography with structural a priori from fluorescence diffuse optical tomography

NASA Astrophysics Data System (ADS)

Ma, Wenjuan; Gao, Feng; Duan, Linjing; Zhu, Qingzhen; Wang, Xin; Zhang, Wei; Wu, Linhui; Yi, Xi; Zhao, Huijuan

2012-03-01

We obtain absorption and scattering reconstructed images by incorporating a priori information of target location obtained from fluorescence diffuse optical tomography (FDOT) into the diffuse optical tomography (DOT). The main disadvantage of DOT lies in the low spatial resolution resulting from highly scattering nature of tissue in the near-infrared (NIR), but one can use it to monitor hemoglobin concentration and oxygen saturation simultaneously, as well as several other cheomphores such as water, lipids, and cytochrome-c-oxidase. Up to date, extensive effort has been made to integrate DOT with other imaging modalities such as MRI, CT, to obtain accurate optical property maps of the tissue. However, the experimental apparatus is intricate. In this study, DOT image reconstruction algorithm that incorporates a prior structural information provided by FDOT is investigated in an attempt to optimize recovery of a simulated optical property distribution. By use of a specifically designed multi-channel time-correlated single photon counting system, the proposed scheme in a transmission mode is experimentally validated to achieve simultaneous reconstruction of the fluorescent yield, lifetime, absorption and scattering coefficient. The experimental results demonstrate that the quantitative recovery of the tumor optical properties has doubled and the spatial resolution improves as well by applying the new improved method.

Perceiving environmental structure from optical motion

NASA Technical Reports Server (NTRS)

Lappin, Joseph S.

1991-01-01

Generally speaking, one of the most important sources of optical information about environmental structure is known to be the deforming optical patterns produced by the movements of the observer (pilot) or environmental objects. As an observer moves through a rigid environment, the projected optical patterns of environmental objects are systematically transformed according to their orientations and positions in 3D space relative to those of the observer. The detailed characteristics of these deforming optical patterns carry information about the 3D structure of the objects and about their locations and orientations relative to those of the observer. The specific geometrical properties of moving images that may constitute visually detected information about the shapes and locations of environmental objects is examined.

The optical spectrum of ternary alloy BBi1-xAsx

NASA Astrophysics Data System (ADS)

Yalcin, Battal G.; Aslan, M.; Ozcan, M. H.; Rahnamaye Aliabad, H. A.

2016-06-01

Among the III-V semiconductors, boron BBi and BAs as well as their alloys have attracted both scientific and technological interest in recent years. We present a calculation of the structural, electronic and optical properties of ternary alloy BBi1-xAsx by means of the WIEN2k software package. The exchange-correlation potential is treated by the generalized gradient approximation (GGA) within the schema of Wu and Cohen. Also, we have used the modified Becke-Johnson (mBJ) formalism to improve the band gap results. All the calculations have been performed after geometry optimization. In this study, we have investigated structural properties such as the lattice constant (a0), bulk modulus (B0) and its pressure derivative (B‧), and calculated the electronic band structures of the studied materials. Accurate calculation of linear optical properties, such as real (ɛ 1) and imaginary (ɛ 2) dielectric functions, reflectivity (R), electron energy loss spectrum, absorption coefficient (α), refractive index (n) and sum rule (Neff) are investigated. Our obtained results for studied binary compounds, BBi and BAs, fairly coincide with other theoretical calculations and experimental measurements. According to the best of our knowledge, no experimental or theoretical data are presently available for the studied ternary alloy BBi1-xAsx (0 < x < 1). The role of electronic band structure calculation with regards to the linear optical properties of BBi1-xAsx is discussed. The effect of the spin-orbit interaction (SOI) is also investigated and found to be quite small.

On the optical properties of carbon nanotubes. Part I. A general formula for the dynamical optical conductivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rasmussen, Morten Grud, E-mail: morteng@math.aau.dk; Ricaud, Benjamin, E-mail: benjamin.ricaud@epfl.ch; Savoie, Baptiste, E-mail: baptiste.savoie@gmail.com

2016-02-15

This paper is the first one in a series of two articles in which we revisit the optical properties of single-walled carbon nanotubes (SWNTs). Produced by rolling up a graphene sheet, SWNTs owe their intriguing properties to their cylindrical quasi-one-dimensional (quasi-1D) structure (the ratio length/radius is experimentally of order of 10{sup 3}). We model SWNT by circular cylinders of small diameters on the surface of which the conduction electron gas is confined by the electric field generated by the fixed carbon ions. The pair-interaction potential considered is the 3D Coulomb potential restricted to the cylinder. To reflect the quasi-1D structure,more » we introduce a 1D effective many-body Hamiltonian which is the starting-point of our analysis. To investigate the optical properties, we consider a perturbation by a uniform time-dependent electric field modeling an incident light beam along the longitudinal direction. By using Kubo’s method, we derive within the linear response theory an asymptotic expansion in the low-temperature regime for the dynamical optical conductivity at fixed density of particles. The leading term only involves the eigenvalues and associated eigenfunctions of the (unperturbed) 1D effective many-body Hamiltonian and allows us to account for the sharp peaks observed in the optical absorption spectrum of SWNT.« less

Optics. Observation of optical polarization Möbius strips.

PubMed

Bauer, Thomas; Banzer, Peter; Karimi, Ebrahim; Orlov, Sergej; Rubano, Andrea; Marrucci, Lorenzo; Santamato, Enrico; Boyd, Robert W; Leuchs, Gerd

2015-02-27

Möbius strips are three-dimensional geometrical structures, fascinating for their peculiar property of being surfaces with only one "side"—or, more technically, being "nonorientable" surfaces. Despite being easily realized artificially, the spontaneous emergence of these structures in nature is exceedingly rare. Here, we generate Möbius strips of optical polarization by tightly focusing the light beam emerging from a q-plate, a liquid crystal device that modifies the polarization of light in a space-variant manner. Using a recently developed method for the three-dimensional nanotomography of optical vector fields, we fully reconstruct the light polarization structure in the focal region, confirming the appearance of Möbius polarization structures. The preparation of such structured light modes may be important for complex light beam engineering and optical micro- and nanofabrication. Copyright © 2015, American Association for the Advancement of Science.

The features of self-assembling organic bilayers important to the formation of anisotropic inorganic materials in microgravity conditions

NASA Technical Reports Server (NTRS)

Talham, Daniel R.; Adair, James H.

2005-01-01

Materials with directional properties are opening new horizons in a variety of applications including chemistry, electronics, and optics. Structural, optical, and electrical properties can be greatly augmented by the fabrication of composite materials with anisotropic microstructures or with anisotropic particles uniformly dispersed in an isotropic matrix. Examples include structural composites, magnetic and optical recording media, photographic film, certain metal and ceramic alloys, and display technologies including flat panel displays. The new applications and the need for model particles in scientific investigations are rapidly out-distancing the ability to synthesize anisotropic particles with specific chemistries and narrowly distributed physical characteristics (e.g. size distribution, shape, and aspect ratio).

Morphology, structure and optical properties of hydrothermally synthesized CeO2/CdS nanocomposites

NASA Astrophysics Data System (ADS)

Mohanty, Biswajyoti; Nayak, J.

2018-04-01

CeO2/CdS nanocomposites were synthesized using a two-step hydrothermal technique. The effects of precursor concentration on the optical and structural properties of the CeO2/CdS nanoparticles were systematically studied. The morphology, composition and the structure of the CeO2/CdS nanocomposite powder were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectrum analysis (EDXA) and X-ray diffraction (XRD), respectively. The optical properties of CeO2/CdS nanocomposites were studied by UV-vis absorption and photoluminescence (PL) spectroscopy. The optical band gaps of the CeO2/CdS nanopowders ranged from 2.34 eV to 2.39 eV as estimated from the UV-vis absorption. In the room temperature photoluminescence spectrum of CeO2/CdS nanopowder, a strong blue emission band was observed at 400 nm. Since the powder shows strong visible luminescence, it may be used as a blue phosphor in future. The original article published with this DOI was submitted in error. The correct article was inadvertently left out of the original submission. This has been rectified and the correct article was published online on 16 April 2018.

Optical and electrical properties of polycrystalline and amorphous Al-Ti thin films

NASA Astrophysics Data System (ADS)

Canulescu, S.; Borca, C. N.; Rechendorff, K.; Davidsdóttir, S.; Pagh Almtoft, K.; Nielsen, L. P.; Schou, J.

2016-04-01

The structural, optical, and transport properties of sputter-deposited Al-Ti thin films have been investigated as a function of Ti alloying with a concentration ranging from 2% to 46%. The optical reflectivity of Al-Ti films at visible and near-infrared wavelengths decreases with increasing Ti content. X-ray absorption fine structure measurements reveal that the atomic ordering around Ti atoms increases with increasing Ti content up to 20% and then decreases as a result of a transition from a polycrystalline to amorphous structure. The transport properties of the Al-Ti films are influenced by electron scattering at the grain boundaries in the case of polycrystalline films and static defects, such as anti-site effects and vacancies in the case of the amorphous alloys. The combination of Ti having a real refractive index (n) comparable with the extinction coefficient (k) and Al with n much smaller than k allows us to explore the parameter space for the free-electron behavior in transition metal-Al alloys. The free electron model, applied for the polycrystalline Al-Ti films with Ti content up to 20%, leads to an optical reflectance at near infrared wavelengths that scales linearly with the square root of the electrical resistivity.

First-Principles Study of the Structural, Optical, Dynamical and Thermodynamic Properties of BaZnO2 Under Pressure

NASA Astrophysics Data System (ADS)

Wang, Yi-Xian; Hu, Cui-E.; Chen, Yang-Mei; Cheng, Yan; Ji, Guang-Fu

2016-11-01

The structural, optical, dynamical, and thermodynamic properties of BaZnO2 under pressure are studied based on the density functional theory. The calculated structural parameters are consistent with the available experimental data. In the ground state, the electronic band structure and density of states indicate that BaZnO2 is an insulator with a direct gap of 2.2 eV. The Mulliken charges are also analyzed to characterize the bonding property. After the structural relaxation, the optical properties are studied. It is found that the dielectric function of E Vert x and EVert y are isotropic, whereas the EVert x and EVert z are anisotropic. The effect of pressure on the energy-loss function in the ultraviolet region becomes more obvious as the pressure increases. Furthermore, the dynamical properties under different pressures are investigated using the finite displacement method. We find that the P3121 phase of BaZnO2 is dynamically stable under the pressure ranging from 0 GPa to 30 GPa. The phonon dispersion curves, phonon density of states, vibrational modes and atoms that contribute to these vibrations at {{\\varvec{Γ }}} point under different pressures are also reported in this work. Finally, by employing the quasi-harmonic approximation, the thermodynamic properties such as the temperature dependence of the thermal expansion coefficient, specific heat, entropy and Gibbs free energy under different pressures are investigated. It is found that the influences of the temperature on the heat capacity are much more significant than that of the pressure on it.

Bioinspired peptide nanotubes: deposition technology, basic physics and nanotechnology applications.

PubMed

Rosenman, G; Beker, P; Koren, I; Yevnin, M; Bank-Srour, B; Mishina, E; Semin, S

2011-02-01

Synthetic peptide monomers can self-assemble into PNM such as nanotubes, nanospheres, hydrogels, etc. which represent a novel class of nanomaterials. Molecular recognition processes lead to the formation of supramolecular PNM ensembles containing crystalline building blocks. Such low-dimensional highly ordered regions create a new physical situation and provide unique physical properties based on electron-hole QC phenomena. In the case of asymmetrical crystalline structure, basic physical phenomena such as linear electro-optic, piezoelectric, and nonlinear optical effects, described by tensors of the odd rank, should be explored. Some of the PNM crystalline structures permit the existence of spontaneous electrical polarization and observation of ferroelectricity. The PNM crystalline arrangement creates highly porous nanotubes when various residues are packed into structural network with specific wettability and electrochemical properties. We report in this review on a wide research of PNM intrinsic physical properties, their electronic and optical properties related to QC effect, unique SHG, piezoelectricity and ferroelectric spontaneous polarization observed in PNT due to their asymmetric structure. We also describe PNM wettability phenomenon based on their nanoporous structure and its influence on electrochemical properties in PNM. The new bottom-up large scale technology of PNT physical vapor deposition and patterning combined with found physical effects at nanoscale, developed by us, opens the avenue for emerging nanotechnology applications of PNM in novel fields of nanophotonics, nanopiezotronics and energy storage devices. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.

Electronic energy loss spectra from mono-layer to few layers of phosphorene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohan, Brij, E-mail: brijmohanhpu@yahoo.com; Thakur, Rajesh; Ahluwalia, P. K.

2016-05-23

Using first principles calculations, electronic and optical properties of few-layers phosphorene has been investigated. Electronic band structure show a moderate band gap of 0.9 eV in monolayer phosphorene which decreases with increasing number of layers. Optical properties of few-layers of phosphorene in infrared and visible region shows tunability with number of layers. Electron energy loss function has been plotted and huge red shift in plasmonic behaviours is found. These tunable electronic and optical properties of few-layers of phosphorene can be useful for the applications of optoelectronic devices.

Optical properties and progressive sterical hindering in pyridinium phenoxides

NASA Astrophysics Data System (ADS)

Boeglin, A.; Barsella, A.; Fort, A.; Mançois, F.; Rodriguez, V.; Diemer, V.; Chaumeil, H.; Defoin, A.; Jacques, P.; Carré, C.

2007-07-01

Pyridinium phenoxides are model compounds associating large dipole moments with high optical nonlinearities. A progression of sterically hindered forms of such zwitterions has been synthesized in order to investigate their structure/property relationships. Their UV-vis absorption in acetonitrile has been analyzed as a function of concentration in order to assess the presence of aggregates and the level of protonation. The quadratic optical properties have been measured by the EFISH and hyper-Rayleigh techniques and are interpreted via semi-empirical calculations. The solvation model used leads to results that agree with our experimental findings indicating an increased response for intermediate twist angles.

Electrical and Optical Characteristics of Undoped and Se-Doped Bi2S3 Transistors

NASA Astrophysics Data System (ADS)

Kilcoyne, Colin; Alsaqqa, Ali; Rahman, Ajara A.; Whittaker-Brooks, Luisa; Sambandamurthy, G.

Semiconducting chalcogenides have been drawing increased attention due to their interesting physical properties, especially in low dimensional structures. Bi2S3 has demonstrated a high optical absorption coefficient, a large bulk mobility, small bandgap, high Seebeck coefficient, and low thermal conductivity. These properties make it a good candidate for optical, electric and thermoelectric applications. However, control over the electrical properties for enhanced thermoelectric performance and optical applications is desired. We present electrical transport and optical properties from individual nanowire and few-layer transistors of single crystalline undoped and Se-doped Bi2S3-xSex. All devices exhibit n-type semiconducting behavior and the ON/OFF ratio, mobility, and conductivity noise behavior are studied as functions of dopant concentration, temperature, and charge carrier density in different conduction regimes. The roles of dopant driven scattering mechanisms and mobility/carrier density fluctuations will be discussed. The potential for this series of materials as optical and electrical switches will be presented. NSF DMR.

Plasmon-enhanced versatile optical nonlinearities in a Au-Ag-Au multi-segmental hybrid structure.

PubMed

Yao, Lin-Hua; Zhang, Jun-Pei; Dai, Hong-Wei; Wang, Ming-Shan; Zhang, Lu-Man; Wang, Xia; Han, Jun-Bo

2018-06-27

A Au-Ag-Au multi-segmental hybrid structure has been synthesized by using an electrodeposition method based on an anodic aluminum oxide (AAO) membrane. The third-order optical nonlinearities, second harmonic generation (SHG) and photoluminescence (PL) properties containing ultrafast supercontinuum generation and plasmon mediated thermal emission have been investigated. Significant optical enhancements have been obtained near surface plasmon resonance wavelength in all the abovementioned nonlinear processes. Comparative studies between the Au-Ag-Au multi-segmental hybrid structure and the corresponding single-component Au and Ag hybrid structures demonstrate that the Au-Ag-Au multi-segmental hybrid structure has much larger optical nonlinearities than its counterparts. These results demonstrate that the Au-Ag-Au hybrid structure is a promising candidate for applications in plasmonic devices and enhancement substrates.

Fast optical detecting media based on semiconductor nanostructures for recording images obtained using charges of free photocarriers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasherininov, P. G., E-mail: peter.kasherininov@mail.ioffe.ru; Tomasov, A. A.; Beregulin, E. V.

2011-01-15

Available published data on the properties of optical recording media based on semiconductor structures are reviewed. The principles of operation, structure, parameters, and the range of application for optical recording media based on MIS structures formed of photorefractive crystals with a thick layer of insulator and MIS structures with a liquid crystal as the insulator (the MIS LC modulators), as well as the effect of optical bistability in semiconductor structures (semiconductor MIS structures with nanodimensionally thin insulator (TI) layer, M(TI)S nanostructures). Special attention is paid to recording media based on the M(TI)S nanostructures promising for fast processing of highly informativemore » images and to fabrication of optoelectronic correlators of images for noncoherent light.« less

In vivo assessment of optical properties of melanocytic skin lesions and differentiation of melanoma from non-malignant lesions by high-definition optical coherence tomography.

PubMed

Boone, M A L M; Suppa, M; Dhaenens, F; Miyamoto, M; Marneffe, A; Jemec, G B E; Del Marmol, V; Nebosis, R

2016-01-01

One of the most challenging problems in clinical dermatology is the early detection of melanoma. Reflectance confocal microscopy (RCM) is an added tool to dermoscopy improving considerably diagnostic accuracy. However, diagnosis strongly depends on the experience of physicians. High-definition optical coherence tomography (HD-OCT) appears to offer additional structural and cellular information on melanocytic lesions complementary to that of RCM. However, the diagnostic potential of HD-OCT seems to be not high enough for ruling out the diagnosis of melanoma if based on morphology analysis. The aim of this paper is first to quantify in vivo optical properties such as light attenuation in melanocytic lesions by HD-OCT. The second objective is to determine the best critical value of these optical properties for melanoma diagnosis. The technique of semi-log plot whereby an exponential function becomes a straight line has been implemented on HD-OCT signals coming from four successive skin layers (epidermis, upper papillary dermis, deeper papillary dermis and superficial reticular dermis). This permitted the HD-OCT in vivo measurement of skin entrance signal (SES), relative attenuation factor normalized for the skin entrance signal (µ raf1) and half value layer (z 1/2). The diagnostic accuracy of HD-OCT for melanoma detection based on the optical properties, µ raf1 , SES and z 1/2 was high (95.6, 82.2 and 88.9 %, respectively). High negative predictive values could be found for these optical properties (96.7, 89.3 and 96.3 %, respectively) compared to morphologic assessment alone (89.9 %), reducing the risk of mistreating a malignant lesion to a more acceptable level (3.3 % instead of 11.1 %). HD-OCT seems to enable the combination of in vivo morphological analysis of cellular and 3-D micro-architectural structures with in vivo analysis of optical properties of tissue scatterers in melanocytic lesions. In vivo HD-OCT analysis of optical properties permits melanoma diagnosis with higher accuracy than in vivo HD-OCT analysis of morphology alone.

Visual optics and ecomorphology of the growing shark eye: a comparison between deep and shallow water species.

PubMed

Litherland, Lenore; Collin, Shaun P; Fritsches, Kerstin A

2009-11-01

Elasmobranch fishes utilise their vision as an important source of sensory information, and a range of visual adaptations have been shown to reflect the ecological diversity of this vertebrate group. This study investigates the hypotheses that visual optics can predict differences in habitat and behaviour and that visual optics change with ontogenetic growth of the eye to maintain optical performance. The study examines eye structure, pupillary movement, transmission properties of the ocular media, focal properties of the lens, tapetum structure and variations in optical performance with ontogenetic growth in two elasmobranch species: the carcharhinid sandbar shark, Carcharhinus plumbeus, inhabiting nearshore coastal waters, and the squalid shortspine spurdog, Squalus mitsukurii, inhabiting deeper waters of the continental shelf and slope. The optical properties appear to be well tuned for the visual needs of each species. Eyes continue to grow throughout life, resulting in an ontogenetic shift in the focal ratio of the eye. The eyes of C. plumbeus are optimised for vision under variable light conditions, which change during development as the animal probes new light environments in its search for food and mates. By contrast, the eyes of S. mitsukurii are specifically adapted to enhance retinal illumination within a dim light environment, and the detection of bioluminescent prey may be optimised with the use of lenticular short-wavelength-absorbing filters. Our findings suggest that the light environment strongly influences optical features in this class of vertebrates and that optical properties of the eye may be useful predictors of habitat and behaviour for lesser-known species of this vertebrate group.

Coupled resonator optical waveguides based on silicon-on-insulator photonic wires

NASA Astrophysics Data System (ADS)

Xia, Fengnian; Sekaric, Lidija; O'Boyle, Martin; Vlasov, Yurii

2006-07-01

Coupled resonator optical waveguides (CROWs) comprised of up to 16 racetrack resonators based on silicon-on-insulator (SOI) photonic wires were fabricated and characterized. The optical properties of the CROWs were simulated using measured single resonator parameters based on a matrix approach. The group delay property of CROWs was also analyzed. The SOI based CROWs consisting of multiple resonators have extremely small footprints and can find applications in optical filtering, dispersion compensation, and optical buffering. Moreover, such CROW structure is a promising candidate for exploration of low light level nonlinear optics due to its resonant nature and compact mode size (˜0.1μm2) in photonic wire.

Optical limiting in gelatin stabilized Cu-PVP nanocomposite colloidal suspension

NASA Astrophysics Data System (ADS)

Tamgadge, Y. S.; Gedam, P. P.; Thakare, N. B.; Talwatkar, S. S.; Sunatkari, A. L.; Muley, G. G.

2018-05-01

This article illustrates investigations on optical limiting properties of Cu-PVP nanocomposite colloidal suspension. Gelatin stabilized Cu nanoparticles have been synthesized using chemical reduction method and thin films in PVP matrix have been obtained using spin coating technique. Thin films have been characterized by X-ray diffraction (XRD), Ultraviolet-visible (UV-vis) spectroscopy, etc. for structural and linear optical studies. Optical limiting properties of Colloidal Cu-PVP nanocomposites have been investigated at 808 nm diode CW laser. Minimum optical limiting threshold was found for GCu3-PVP nanocomposites sample. The strong optical limiting is thermal in origin as CW laser is used and effects are attributed to thermal lensing effect.

Gram-scale synthesis of single-crystalline graphene quantum dots with superior optical properties.

PubMed

Wang, Liang; Wang, Yanli; Xu, Tao; Liao, Haobo; Yao, Chenjie; Liu, Yuan; Li, Zhen; Chen, Zhiwen; Pan, Dengyu; Sun, Litao; Wu, Minghong

2014-10-28

Graphene quantum dots (GQDs) have various alluring properties and potential applications, but their large-scale applications are limited by current synthetic methods that commonly produce GQDs in small amounts. Moreover, GQDs usually exhibit polycrystalline or highly defective structures and thus poor optical properties. Here we report the gram-scale synthesis of single-crystalline GQDs by a facile molecular fusion route under mild and green hydrothermal conditions. The synthesis involves the nitration of pyrene followed by hydrothermal treatment in alkaline aqueous solutions, where alkaline species play a crucial role in tuning their size, functionalization and optical properties. The single-crystalline GQDs are bestowed with excellent optical properties such as bright excitonic fluorescence, strong excitonic absorption bands extending to the visible region, large molar extinction coefficients and long-term photostability. These high-quality GQDs can find a large array of novel applications in bioimaging, biosensing, light emitting diodes, solar cells, hydrogen production, fuel cells and supercapacitors.

Theoretical Calculations of Refractive Properties for Hg3Te2Cl2 Crystals

NASA Astrophysics Data System (ADS)

Bokotey, O. V.

2016-05-01

This paper reviews the optical properties, such as refractive index, optical dielectric constant, and reflection coefficient of the Hg3Te2Cl2 crystals. The applications of the Hg3X2Y2 crystals as electronic, optical, and optoelectronic devices are very much determined by the nature and magnitude of these fundamental material properties. The origin of chemical bonding in the crystals is very important for definition of the physical and chemical properties. The main structural feature of the Hg3X2Y2 crystals is the presence of covalent pyramids [XHg3] and linear X-Hg-X groups. Optical properties are calculated according to the model proposed by Harrison. The refractive index in the spectral region far from the absorption edge is determined within the generalized single-oscillator model. The calculated results are found to be in good agreement with experimental data.

UV-Vis spectroscopy of tyrosine side-groups in studies of protein structure. Part 1: basic principles and properties of tyrosine chromophore.

PubMed

Antosiewicz, Jan M; Shugar, David

Spectroscopic properties of tyrosine residues may be employed in structural studies of proteins. Here we discuss several different types of UV-Vis spectroscopy, like normal, difference and second-derivative UV absorption spectroscopy, fluorescence spectroscopy, linear and circular dichroism spectroscopy, and Raman spectroscopy, and corresponding optical properties of the tyrosine chromophore, phenol, which are used to study protein structure.

UV-Vis spectroscopy of tyrosine side-groups in studies of protein structure. Part 1: basic principles and properties of tyrosine chromophore.

PubMed

Antosiewicz, Jan M; Shugar, David

2016-06-01

Spectroscopic properties of tyrosine residues may be employed in structural studies of proteins. Here we discuss several different types of UV-Vis spectroscopy, like normal, difference and second-derivative UV absorption spectroscopy, fluorescence spectroscopy, linear and circular dichroism spectroscopy, and Raman spectroscopy, and corresponding optical properties of the tyrosine chromophore, phenol, which are used to study protein structure.

Structural, vibrational and theoretical studies of anilinium trichloroacetate: New hydrogen bonded molecular crystal with nonlinear optical properties

NASA Astrophysics Data System (ADS)

Tanak, H.; Pawlus, K.; Marchewka, M. K.; Pietraszko, A.

2014-01-01

In this work, we report a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of the potential nonlinear optical (NLO) material anilinium trichloroacetate. The FT-IR and FT-Raman spectra of the compound have been recorded together between 4000-80 cm-1 and 3600-80 cm-1 regions, respectively. The compound crystallizes in the noncentrosymmetric space group of monoclinic system. The optimized molecular structure, vibrational wavenumbers, IR intensities and Raman activities have been calculated by using density functional method (B3LYP) with 6-311++G(d,p) as higher basis set. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. DSC measurements on powder samples do not indicate clearly on the occurrence of phase transitions in the temperature 113-293 K. The Kurtz and Perry powder reflection technique appeared to be very effective in studies of second-order nonlinear optical properties of the molecule. The non-linear optical properties are also addressed theoretically. The predicted NLO properties of the title compound are much greater than ones of urea. In addition, DFT calculations of the title compound, molecular electrostatic potential, frontier orbitals and thermodynamic properties were also performed at 6-311++G(d,p) level of theory. For title crystal the SHG efficiency was estimated by Kurtz-Perry method to be deff = 0.70 deff (KDP).

Structural, vibrational and theoretical studies of anilinium trichloroacetate: new hydrogen bonded molecular crystal with nonlinear optical properties.

PubMed

Tanak, H; Pawlus, K; Marchewka, M K; Pietraszko, A

2014-01-24

In this work, we report a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of the potential nonlinear optical (NLO) material anilinium trichloroacetate. The FT-IR and FT-Raman spectra of the compound have been recorded together between 4000-80 cm(-1) and 3600-80 cm(-1) regions, respectively. The compound crystallizes in the noncentrosymmetric space group of monoclinic system. The optimized molecular structure, vibrational wavenumbers, IR intensities and Raman activities have been calculated by using density functional method (B3LYP) with 6-311++G(d,p) as higher basis set. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. DSC measurements on powder samples do not indicate clearly on the occurrence of phase transitions in the temperature 113-293 K. The Kurtz and Perry powder reflection technique appeared to be very effective in studies of second-order nonlinear optical properties of the molecule. The non-linear optical properties are also addressed theoretically. The predicted NLO properties of the title compound are much greater than ones of urea. In addition, DFT calculations of the title compound, molecular electrostatic potential, frontier orbitals and thermodynamic properties were also performed at 6-311++G(d,p) level of theory. For title crystal the SHG efficiency was estimated by Kurtz-Perry method to be d(eff)=0.70 d(eff) (KDP). Copyright © 2013 Elsevier B.V. All rights reserved.

Influence of Cu-doping on the structural and optical properties of CaTiO{sub 3} powders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliveira, L.H.; Moura, A.P. de; La Porta, F.A., E-mail: felipe_laporta@yahoo.com.br

2016-09-15

Highlights: • Ca{sub 1−x}Cu{sub x}TiO{sub 3} powders were successfully synthesized via a polymeric precursor method. • Effects of Cu incorporated on the Ca-site into the CaTiO{sub 3} lattice as host matrix has been investigated. • The optical behavior reveals that the Ca{sub 1−x}Cu{sub x}TiO{sub 3} powders have potential applications in emerging technologies. - Abstract: Here, we report on the effect of chemical substitution on the structural and optical properties of Cu-doped CaTiO{sub 3} (CTO) polycrystalline powders synthesized by the polymeric precursor method. Our findings are discussed based on the structural order-disorder effects originating from the modification of the Ca{sub 1−x}Cu{submore » x}TiO{sub 3} microcrystal matrix. These results may elucidate the compositional modulation and methods of controlling the structural design, as well as reveal the changes in the optical behavior of this system at an atomic level.« less

The properties of RE-TM magneto-optical films

NASA Astrophysics Data System (ADS)

Lee, Z. Y.; Miao, X. S.; Zhu, P.; Hu, Y. S.; Wan, D. F.; Dai, D. W.; Chen, S. B.; Lin, G. Q.

1992-09-01

In this paper, the magnetic, magneto-optical and galvonomagnetic properties, and their temperature dependence for LRE-TM SmCo, SmCoDy and HRE-TM TbFeCo magneto-optical films as high density recording media prepared by rf magnetron sputtering or evaporation are reported. By adding Dy to SmCo thin film, the SmCoDy thin film is more suitable for magneto-optical recording, its domain size being below 0.63 μm. The Kerr enhancement and corrosion protective effects of AIN and AlSiN for optimum design of the multi-layer structure of magneto-optical disk are described. The instruments of measuring the magneto-optical Kerr effect and magneto-optical recording domain characteristics of thin films are reviewed.

Structural, electronic and optical properties of well-known primary explosive: Mercury fulminate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yedukondalu, N.; Vaitheeswaran, G., E-mail: gvsp@uohyd.ernet.in

2015-11-28

Mercury Fulminate (MF) is one of the well-known primary explosives since 17th century and it has rendered invaluable service over many years. However, the correct molecular and crystal structures are determined recently after 300 years of its discovery. In the present study, we report pressure dependent structural, elastic, electronic and optical properties of MF. Non-local correction methods have been employed to capture the weak van der Waals interactions in layered and molecular energetic MF. Among the non-local correction methods tested, optB88-vdW method works well for the investigated compound. The obtained equilibrium bulk modulus reveals that MF is softer than themore » well known primary explosives Silver Fulminate (SF), silver azide and lead azide. MF exhibits anisotropic compressibility (b > a > c) under pressure, consequently the corresponding elastic moduli decrease in the following order: C{sub 22} > C{sub 11} > C{sub 33}. The structural and mechanical properties suggest that MF is more sensitive to detonate along c-axis (similar to RDX) due to high compressibility of Hg⋯O non-bonded interactions along that axis. Electronic structure and optical properties were calculated including spin-orbit (SO) interactions using full potential linearized augmented plane wave method within recently developed Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The calculated TB-mBJ electronic structures of SF and MF show that these compounds are indirect bandgap insulators. Also, SO coupling is found to be more pronounced for 4d and 5d-states of Ag and Hg atoms of SF and MF, respectively. Partial density of states and electron charge density maps were used to describe the nature of chemical bonding. Ag—C bond is more directional than Hg—C bond which makes SF to be more unstable than MF. The effect of SO coupling on optical properties has also been studied and found to be significant for both (SF and MF) of the compounds.« less

Estimation and imaging of breast lesions using a two-layer tissue structure by ultrasound-guided optical tomography

PubMed Central

Xu, Yan; Zhu, Quing

2015-01-01

Abstract. A new two-step estimation and imaging method is developed for a two-layer breast tissue structure consisting of a breast tissue layer and a chest wall underneath. First, a smaller probe with shorter distance source-detector pairs was used to collect the reflected light mainly from the breast tissue layer. Then, a larger probe with 9×14 source-detector pairs and a centrally located ultrasound transducer was used to collect reflected light from the two-layer tissue structure. The data collected from the smaller probe were used to estimate breast tissue optical properties. With more accurate estimation of the average breast tissue properties, the second layer properties can be assessed from data obtained from the larger probe. Using this approach, the unknown variables have been reduced from four to two and the estimated bulk tissue optical properties are more accurate and robust. In addition, a two-step reconstruction using a genetic algorithm and conjugate gradient method is implemented to simultaneously reconstruct the absorption and reduced scattering maps of targets inside a two-layer tissue structure. Simulations and phantom experiments have been performed to validate the new reconstruction method, and a clinical example is given to demonstrate the feasibility of this approach. PMID:26046722

Osmotic-pressure-controlled concentration of colloidal particles in thin-shelled capsules

NASA Astrophysics Data System (ADS)

Kim, Shin-Hyun; Park, Jin-Gyu; Choi, Tae Min; Manoharan, Vinothan N.; Weitz, David A.

2014-01-01

Colloidal crystals are promising structures for photonic applications requiring dynamic control over optical properties. However, for ease of processing and reconfigurability, the crystals should be encapsulated to form ‘ink’ capsules rather than confined in a thin film. Here we demonstrate a class of encapsulated colloidal photonic structures whose optical properties can be controlled through osmotic pressure. The ordering and separation of the particles within the microfluidically created capsules can be tuned by changing the colloidal concentration through osmotic pressure-induced control of the size of the individual capsules, modulating photonic stop band. The rubber capsules exhibit a reversible change in the diffracted colour, depending on osmotic pressure, a property we call osmochromaticity. The high encapsulation efficiency and capsule uniformity of this microfluidic approach, combined with the highly reconfigurable shapes and the broad control over photonic properties, make this class of structures particularly suitable for photonic applications such as electronic inks and reflective displays.

Characterization of human scalp hairs by optical low-coherence reflectometry

NASA Astrophysics Data System (ADS)

Wang, X. J.; Milner, T. E.; Dhond, R. P.; Sorin, W. V.; Newton, S. A.; Nelson, J. S.

1995-03-01

Optical low-coherence reflectometry is used to investigate the internal structure and optical properties of human scalp hair. Regardless of hair color, the refractive index of the cortical region remains within the range of 1.56-1.59. The amplitude of the backscattered infrared light coupled into different-colored hair confirms the relative melanin content. Discontinuities in the refractive index permit identification of distinct structural layers within the hair shaft.

Holographic Structuring of Elastomer Actuator: First True Monolithic Tunable Elastomer Optics.

PubMed

Ryabchun, Alexander; Kollosche, Matthias; Wegener, Michael; Sakhno, Oksana

2016-12-01

Volume diffraction gratings (VDGs) are inscribed selectively by diffusive introduction of benzophenone and subsequent UV-holographic structuring into an electroactive dielectric elastomer actuator (DEA), to afford a continuous voltage-controlled grating shift of 17%. The internal stress coupling of DEA and optical domain allows for a new generation of true monolithic tunable elastomer optics with voltage controlled properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectroscopic Ellipsometry Studies of Ag and ZnO Thin Films and Their Interfaces for Thin Film Photovoltaics

NASA Astrophysics Data System (ADS)

Sainju, Deepak

Many modern optical and electronic devices, including photovoltaic devices, consist of multilayered thin film structures. Spectroscopic ellipsometry (SE) is a critically important characterization technique for such multilayers. SE can be applied to measure key parameters related to the structural, optical, and electrical properties of the components of multilayers with high accuracy and precision. One of the key advantages of this non-destructive technique is its capability of monitoring the growth dynamics of thin films in-situ and in real time with monolayer level precision. In this dissertation, the techniques of SE have been applied to study the component layer materials and structures used as back-reflectors and as the transparent contact layers in thin film photovoltaic technologies, including hydrogenated silicon (Si:H), copper indium-gallium diselenide (CIGS), and cadmium telluride (CdTe). The component layer materials, including silver and both intrinsic and doped zinc oxide, are fabricated on crystalline silicon and glass substrates using magnetron sputtering techniques. These thin films are measured in-situ and in real time as well as ex-situ by spectroscopic ellipsometry in order to extract parameters related to the structural properties, such as bulk layer thickness and surface roughness layer thickness and their time evolution, the latter information specific to real time measurements. The index of refraction and extinction coefficient or complex dielectric function of a single unknown layer can also be obtained from the measurement versus photon energy. Applying analytical expressions for these optical properties versus photon energy, parameters that describe electronic transport, such as electrical resistivity and electron scattering time, can be extracted. The SE technique is also performed as the sample is heated in order to derive the effects of annealing on the optical properties and derived electrical transport parameters, as well as the intrinsic temperature dependence of these properties and parameters. One of the major achievements of this dissertation research is the characterization of the thickness and optical properties of the interface layer formed between the silver and zinc oxide layers in a back-reflector structure used in thin film photovoltaics. An understanding of the impact of these thin film material properties on solar cell device performance has been complemented by applying reflectance and transmittance spectroscopy as well as simulations of cell performance.

Starch-assisted synthesis and optical properties of ZnS nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Xiuying, E-mail: xiuyingt@yahoo.com; Wen, Jin; Wang, Shumei

Highlights: • ZnS spherical nanostructure was prepared via starch-assisted method. • The crystalline lattice structure, morphologies, chemical and optical properties of ZnS nanoparticles. • The forming mechanism of ZnS nanoparticles. • ZnS spherical nano-structure can show blue emission at 460–500 nm. - Abstract: ZnS nanoparticles are fabricated via starch-assisted method. The effects of different starch amounts on structure and properties of samples are investigated, and the forming mechanism of ZnS nanoparticles is discussed. By X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis)more » spectroscopy and fluorescence (FL) spectrometer, their phases, crystalline lattice structure, morphologies, chemical and optical properties are characterized. The results show that ZnS has polycrystalline spherical structure with the mean diameter of 130 nm. Sample without starch reveals irregular aggregates with particle size distribution of 0.5–2 μm. The band gap value of ZnS is 3.97 eV. The chemical interaction exists between starch molecules and ZnS nanoparticles by hydrogen bonds. The stronger FL emission peaks of ZnS synthesized with starch, indicate a larger content of sulfur vacancies or defects than ZnS synthesized without starch.« less

Electrochemical and physical properties of electroplated CuO thin films.

PubMed

Dhanasekaran, V; Mahalingam, T

2013-01-01

Cupric oxide thin films have been prepared on ITO glass substrates from an aqueous electrolytic bath containing CuSO4 and tartaric acid. Growth mechanism has been analyzed using cyclic voltammetry. The role of pH on the structural, morphological, compositional, electrical and optical properties of CuO films is investigated. The structural studies revealed that the deposited films are polycrystalline in nature with a cubic structure. The preferential orientation of CuO thin films is found to be along (111) plane. X-ray line profile analysis has been carried out to determine the microstructural parameters of CuO thin films. The pyramid shaped grains are observed from SEM and AFM images. The optical band gap energy and electrical activation energy is found to be 1.45 and 0.37 eV, respectively. Also, the optical constants of CuO thin films such as refractive index (n), complex dielectric constant (epsilon) extinction coefficient (k) and optical conductivity (sigma) are evaluated.

Effect of sintering on optical, structural and photoluminescence properties of ZnO thin films prepared by sol-gel process.

PubMed

Vishwas, M; Narasimha Rao, K; Arjuna Gowda, K V; Chakradhar, R P S

2010-09-15

Zinc oxide (ZnO) thin films have been deposited on glass substrates via sol-gel technique using zinc acetate dihydrate as precursor by spin coating of the sol at 2000 rpm. Effects of annealing temperature on optical, structural and photo luminescence properties of the deposited ZnO films have been investigated. The phase transition from amorphous to polycrystalline hexagonal wurtzite structure was observed at an annealing temperature of 400 degrees C. An average transmittance of 87% in the visible region has been obtained at room temperature. The optical transmittance has slightly increased with increase of annealing temperature. The band gap energy was estimated by Tauc's method and found to be 3.22 eV at room temperature. The optical band gap energy has decreased with increasing annealing temperature. The photoluminescence (PL) intensity increased with annealing temperature up to 200 degrees C and decreased at 300 degrees C. Copyright 2010 Elsevier B.V. All rights reserved.

Influence of post-deposition annealing on structural, morphological and optical properties of copper (II) acetylacetonate thin films.

PubMed

Abdel-Khalek, H; El-Samahi, M I; El-Mahalawy, Ahmed M

2018-05-21

In this study, the effect of thermal annealing under vacuum conditions on structural, morphological and optical properties of thermally evaporated copper (II) acetylacetonate, cu(acac) 2 , thin films were investigated. The copper (II) acetylacetonate thin films were deposited using thermal evaporation technique at vacuum pressure ~1 × 10 -5  mbar. The deposited films were thermally annealed at 323, 373, 423, and 473 K for 2 h in vacuum. The thermogravimetric analysis of cu(acac) 2 powder indicated a thermal stability of cu(acac) 2 up to 423 K. The effects of thermal annealing on the structural properties of cu(acac) 2 were evaluated employing X-ray diffraction method and the analysis showed a polycrystalline nature of the as-deposited and annealed films with a preferred orientation in [1¯01] direction. Fourier transformation infrared (FTIR) technique was used to negate the decomposition of copper (II) acetylacetonate during preparation or/and annealing up to 423 K. The surface morphology of the prepared films was characterized by means of field emission scanning electron microscopy (FESEM). A significant enhancement of the morphological properties of cu(acac) 2 thin films was obtained till the annealing temperature reaches 423 K. The variation of optical constants that estimated from spectrophotometric measurements of the prepared thin films was investigated as a function of annealing temperature. The annealing process presented significantly impacted the nonlinear optical properties such as third-order optical susceptibility χ (3) and nonlinear refractive index n 2 of cu(acac) 2 thin films. Copyright © 2018 Elsevier B.V. All rights reserved.

Measuring the Optical Properties of Astrophysical Dust Analogues: Instrumentation and Methods

NASA Technical Reports Server (NTRS)

Rinehart, S. A.; Benford, D. J.; Cataldo, G.; Dwek, E.; Henry, R.; Kinzer, R. E., Jr.; Nuth, J.; Silverberg, R.; Wheeler, C.; Wollack, E.

2011-01-01

Dust is found throughout the universe and plays an important role for a wide range of astrophysical phenomena. In recent years, new infrared facilities have provided powerful new data for understanding these phenomena. However, interpretation of these data is often complicated by a lack of complementary information about the optical properties of astronomically relevant materials. The Optical Properties of Astronomical Silicates with Infrared Techniques (OPASI-T) program at NASA's Goddard Space Flight Center is designed to provide new high-quality laboratory data from which we can derive the optical properties of astrophysical dust analogues. This program makes use of multiple instruments, including new equipment designed and built specifically for this purpose. The suite of instruments allows us to derive optical properties over a wide wavelength range, from the near-infrared through the millimeter, also providing the capability for exploring how these properties depend upon the temperature of the sample. In this paper, we discuss the overall structure of the research program, describe the new instruments that have been developed to meet the science goals, and demonstrate the efficacy of these tools.

Structural, chemical and physical properties of pure and La3+ doped L-Threonine acetate crystals

NASA Astrophysics Data System (ADS)

Senthamizhan, A.; Sambathkumar, K.; Nithiyanantham, S.; Venkatachalapathy, M.; Rajkamal, N.

2017-12-01

The pure and La3+ doped L- Threonine crystals can be grown by slow evaporation techniques. The crystal structure were examined through X-Ray diffraction (XRD) analysis, confirmed the P212121 system. The quantitative nature of dopant can be analyzed with Inductively Coupled Plasma (ICP) study. The Fourier Transform Infra-Red (FTIR) and Fourier Transform (FT- Raman) investigations yields the possible stretching/bonding with their functional groups and the qualitative/quantitative nature of both crystals is analyzed. The optical behavior of crystals can be studied through Ultra Violet (UV) - Visible spectrometer. The mechanical, thermal and decomposition studies can be carried out through Vickers hardness test, Thermo Gravometric Analysis (TGA) and Differential Thermal Analysis (DTA). The Non Linear Optical (NLO) properties are found more than Potassium Phosphate (KDP) through Kurtz powders technique. The dielectric and optical absorption studies for both pure and L-doped crystals were studied and interpreted all the properties. The La3+ dopant increases the properties are investigated.

First-Principles Calculations of Structural, Electronic and Optical Properties of Ternary Semiconductor Alloys ZAs x Sb1- x ( Z = B, Al, Ga, In)

NASA Astrophysics Data System (ADS)

Bounab, S.; Bentabet, A.; Bouhadda, Y.; Belgoumri, Gh.; Fenineche, N.

2017-08-01

We have investigated the structural and electronic properties of the BAs x Sb 1- x , AlAs x Sb 1- x , GaAs x Sb 1- x and InAs x Sb 1- x semiconductor alloys using first-principles calculations under the virtual crystal approximation within both the density functional perturbation theory and the pseudopotential approach. In addition the optical properties have been calculated by using empirical methods. The ground state properties such as lattice constants, both bulk modulus and derivative of bulk modulus, energy gap, refractive index and optical dielectric constant have been calculated and discussed. The obtained results are in reasonable agreement with numerous experimental and theoretical data. The compositional dependence of the lattice constant, bulk modulus, energy gap and effective mass of electrons for ternary alloys show deviations from Vegard's law where our results are in agreement with the available data in the literature.

Electronic structure and optical properties of CuAlO2 under biaxial strain.

PubMed

Ghosh, C K; Sarkar, D; Mitra, M K; Chattopadhyay, K K

2012-06-13

An ab initio calculation has been carried out to investigate the biaxial strain ( - 10.71% < ε < 9.13%) effect on elastic, electronic and optical properties of CuAlO(2). All the elastic constants (c(11), c(12), c(13), c(33)) except c(44) decrease (increase) during tensile (compressive) strain. The band gap is found to decrease in the presence of tensile as well as compressive strain. The relative decrease of the band gap is asymmetric with respect to the sign of the strain. Significant differences between the parallel and perpendicular components of the dielectric constant and the optical properties have been observed due to anisotropic crystal structure. It is further noticed that these properties are easily tunable by strain. Importantly, the collective oscillation of the valence electrons has been identified for light polarized perpendicular to the c-axis. From calculations, it is clear that the tensile strain can enhance the hole mobility as well as the transparency of CuAlO(2).

Electronic structure and optical properties of CuAlO2 under biaxial strain

NASA Astrophysics Data System (ADS)

Ghosh, C. K.; Sarkar, D.; Mitra, M. K.; Chattopadhyay, K. K.

2012-06-01

An ab initio calculation has been carried out to investigate the biaxial strain ( - 10.71% < ɛ < 9.13%) effect on elastic, electronic and optical properties of CuAlO2. All the elastic constants (c11, c12, c13, c33) except c44 decrease (increase) during tensile (compressive) strain. The band gap is found to decrease in the presence of tensile as well as compressive strain. The relative decrease of the band gap is asymmetric with respect to the sign of the strain. Significant differences between the parallel and perpendicular components of the dielectric constant and the optical properties have been observed due to anisotropic crystal structure. It is further noticed that these properties are easily tunable by strain. Importantly, the collective oscillation of the valence electrons has been identified for light polarized perpendicular to the c-axis. From calculations, it is clear that the tensile strain can enhance the hole mobility as well as the transparency of CuAlO2.

Probing optical excitations in chevron-like armchair graphene nanoribbons.

PubMed

Denk, Richard; Lodi-Rizzini, Alberto; Wang, Shudong; Hohage, Michael; Zeppenfeld, Peter; Cai, Jinming; Fasel, Roman; Ruffieux, Pascal; Berger, Reinhard Franz Josef; Chen, Zongping; Narita, Akimitsu; Feng, Xinliang; Müllen, Klaus; Biagi, Roberto; De Renzi, Valentina; Prezzi, Deborah; Ruini, Alice; Ferretti, Andrea

2017-11-30

The bottom-up fabrication of graphene nanoribbons (GNRs) has opened new opportunities to specifically tune their electronic and optical properties by precisely controlling their atomic structure. Here, we address excitation in GNRs with periodic structural wiggles, the so-called chevron GNRs. Based on reflectance difference and high-resolution electron energy loss spectroscopies together with ab initio simulations, we demonstrate that their excited-state properties are of excitonic nature. The spectral fingerprints corresponding to different reaction stages in their bottom-up fabrication are also unequivocally identified, allowing us to follow the exciton build-up from the starting monomer precursor to the final GNR structure.

Characterization and enhanced nonlinear optical limiting response in carbon nanodots dispersed in solid-state hybrid organically modified silica gel glasses

NASA Astrophysics Data System (ADS)

Huang, Li; Zheng, Chan; Guo, Qiaohang; Huang, Dongdong; Wu, Xiukai; Chen, Ling

2018-02-01

Freely dispersed carbon nanodots (CNDs) were introduced into a 3-glycidoxy-propyltrimethoxysilane modified silicate gel glass (i.e. an organically modified silica or ORMOSIL) by a highly efficient and simple sol-gel process, which could be easily extended to prepare functional molecules/nanoparticles solid state optoelectronic devices. Scanning electron microscope imaging, Fourier transform infrared spectroscopy, pore structure measurements, ultraviolet-visible spectroscopy, and fluorescence spectroscopy were used to investigate the surface characteristics, structure, texture, and linear optical properties of the CND/SiO2 ORMOSIL gel glasses. Images and UV/Vis spectra confirmed the successful dispersion of CNDs in the ORMOSIL gel glass. The surface characteristics and pore structure of the host SiO2 matrix were markedly changed through the introduction of the CNDs. The linear optical properties of the guest CNDs were also affected by the sol-gel procedure. The nonlinear optical (NLO) properties of the CNDs were investigated by a nanosecond open-aperture Z-scan technique at 532 nm both in liquid and solid matrices. We found that the NLO response of the CNDs was considerably improved after their incorporation into the ORMOSIL gel glasses. Possible enhancement mechanisms were also explored. The nonlinear extinction coefficient gradually increased while the optical limiting (OL) threshold decreased as the CND doping level was increased. This result suggests that the NLO and OL properties of the composite gel glasses can be optimized by tuning the concentration of CNDs in the gel glass matrix. Our findings show that CND/SiO2 ORMOSIL gel glasses are promising candidates for optical limiters to protect sensitive instruments and human eyes from damage caused by high power lasers.

Optical and optomechanical ultralightweight C/SiC components

NASA Astrophysics Data System (ADS)

Papenburg, Ulrich; Pfrang, Wilhelm; Kutter, G. S.; Mueller, Claus E.; Kunkel, Bernd P.; Deyerler, Michael; Bauereisen, Stefan

1999-11-01

Optical and optomechanical structures based on silicon carbide (SiC) ceramics are becoming increasingly important for ultra- lightweight optical systems that must work in adverse environments. At IABG and Dornier Satellite Systems (DSS) in Munich, a special form of SiC ceramics carbon fiber reinforced silicon carbide (C/SiCR) has been developed partly under ESA and NASA contracts. C/SiCR is a light-weight, high- strength engineering material that features tunable mechanical and thermal properties. It offers exceptional design freedom due to its reduced brittleness and negligible volume shrinkage during processing in comparison to traditional, powder-based ceramics. Furthermore, its rapid fabrication process produces near-net-shape components using conventional NC machining/milling equipment and, thus, provides substantial schedule, cost, and risk savings. These characteristics allow C/SiCR to overcome many of the problems associated with more traditional optical materials. To date, C/SiCR has been used to produce ultra-lightweight mirrors and reflectors, antennas, optical benches, and monolithic and integrated reference structures for a variety of space and terrestrial applications. This paper describes the material properties, optical system and structural design aspects, the forming and manufacturing process including high-temperature joining technology, precision grinding and cladding techniques, and the performance results of a number of C/SiCR optical components we have built.

Nanostructured GdxZn1-xO thin films by nebulizer spray pyrolysis technique: Role of doping concentration on the structural and optical properties

NASA Astrophysics Data System (ADS)

Mariappan, R.; Ponnuswamy, V.; Suresh, P.; Suresh, R.; Ragavendar, M.

2013-07-01

Nanostructured GdxZn1-xO thin films with different Gd concentration from 0% to 10% deposited at 400 °C using the NSP technique. The films were characterized by structural, surface and optical properties, respectively. X-ray diffraction analysis shows that the Gd doped ZnO films have lattice parameters a = 3.2497 Å and c = 5.2018 Å with hexagonal structure and preferential orientation along (0 0 2) plane. The estimated values compare well with the standard values. When film thickness increases from 222 to 240 nm a high visible region transmittance (>70%) is observed. The optical band gap energy, optical constants (n and k), complex dielectric constants (ɛr and ɛi) and optical conductivities (σr and σi) were calculated from optical transmittance data. The optical band gap energy is 3.2 eV for pure ZnO film and 3.6 eV for Gd0.1Zn0.9O film. The PL studies confirm the presence of a strong UV emission peak at 399 nm. Besides, the UV emission of ZnO films decreases with the increase of Gd doping concentration correspondingly the ultra-violet emission is replaced by blue and green emissions.

Ab-initio calculations of structural, electronic, and optical properties of Zn3(VO4)2

NASA Astrophysics Data System (ADS)

Ahmed, Nisar; Mukhtar, S.; Gao, Wei; Zafar Ilyas, Syed

2018-03-01

The structural, electronic, and optical properties of Zn3(VO4)2 are investigated using full potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory (DFT). Various approaches are adopted to treat the exchange and correlation potential energy such as generalized gradient approximation (GGA), GGA+U, and the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential. The calculated band gap of 3.424 eV by TB-mBJ is found to be close to the experimental result (3.3 eV). The optical anisotropy is analyzed through optical constants, such as dielectric function and absorption coefficient along parallel and perpendicular crystal orientations. The absorption coefficient reveals high absorption (1.5× {10}6 {cm}}-1) of photons in the ultraviolet region.

Structural, optical and electrical properties of WO3-Ag nanocomposites for the electro-optical devices

NASA Astrophysics Data System (ADS)

Najafi-Ashtiani, Hamed; Bahari, Ali; Gholipour, Samira; Hoseinzadeh, Siamak

2018-01-01

The composites of tungsten trioxide and silver are synthesized by sodium tungstate and silver nitrate precursors. The structural properties of composite coatings are studied by FTIR, XRD, and XPS. The FTIR analysis of synthesized composite powder corroborated the bonds between tungsten and oxygen elements in WO3 molecules. Furthermore, the XRD spectra show crystalline nature while particle size analysis that is investigated by X-powder software shows average particle size of 24 and 25 nm for samples. The structural analyses show that the addition of silver dopant does not change the stoichiometry of tungsten trioxide and only increase the size of the aggregation in the films. Furthermore, these films have an average approximate roughness of about 10.7, 13.1 and 14.2 nm for sample 1, 2 and 3, respectively. The real and imaginative parts of permittivity are investigated using LCR meter in the frequency range 1 Hz-10 GHz. The optical spectra of composite coatings are characterized in the 300-900 nm wavelength range and the calculation of optical band gaps of them exhibited the directly allowed transition with the values of 3.8 and 3.85 eV. From UV-visible spectroscopy studies, the absorption coefficient of the composite thin films is determined to be of the order of 105 cm- 1 and the obtained refraction and extinction indexes indicated normal dispersive coatings. Due to their optical and electrical properties, the synthesized composite material is a promising candidate for use in electro-optical applicants.

Effect of copper doping on the photocatalytic activity of ZnO thin films prepared by sol-gel method

NASA Astrophysics Data System (ADS)

Saidani, T.; Zaabat, M.; Aida, M. S.; Boudine, B.

2015-12-01

In the present work, we prepared undoped and copper doped ZnO thin films by the sol-gel dip coating method on glass substrates from zinc acetate dissolved in a solution of ethanol. The objective of our work is to study the effect of Cu doping with different concentrations on structural, morphological, optical properties and photocatalytic activity of ZnO thin films. For this purpose, we have used XRD to study the structural properties, and AFM to determine the morphology of the surface of the ZnO thin films. The optical properties and the photocatalytic degradation of the films were examined by UV-visibles spectrophotometer. The Tauc method was used to estimate the optical band gap. The XRD spectra indicated that the films have an hexagonal wurtzite structure, which gradually deteriorated with increasing Cu concentration. The results showed that the incorporation of Cu decreases the crystallite size. The AFM study showed that an increase of the concentration of Cu causes the decrease of the surface roughness, which passes from 20.2 for Un-doped ZnO to 12.16 nm for doped ZnO 5 wt% Cu. Optical measurements have shown that all the deposited films show good optical transmittance (77%-92%) in the visible region and increases the optical gap with increasing Cu concentration. The presence of copper from 1% to 5 wt% in the ZnO thin films is found to decelerate the photocatalytic process.

The origin of luminescence from di[4-(4-diphenylaminophenyl)phenyl]sulfone (DAPSF), a blue light emitter: an X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) study.

PubMed

Zhang, Duo; Zhang, Hui; Zhang, Xiaohong; Sham, Tsun-Kong; Hu, Yongfeng; Sun, Xuhui

2016-03-07

The electronic structure and optical properties of di[4-(4-diphenylaminophenyl)phenyl]sulfone (denoted as DAPSF), a highly efficient fluorophor, have been investigated using X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) spectroscopy at excitation energies across the C, N, O K-edges and the sulfur K-edge. The results indicate that the blue luminescence is mainly related to the sulfur functional group.

Structural and Optical Behaviour of Ar+ Implanted Polycarbonate

NASA Astrophysics Data System (ADS)

Shekhawat, Nidhi; Aggarwal, Sanjeev; Sharma, Annu; Deshpande, S. K.; Nair, K. G. M.

2011-07-01

Effects of 130 keV Ar+ ion implantation on the structural and optical properties of polycarbonate specimens have been studied using Raman, UV-Visible spectroscopy and glancing angle X-ray diffraction techniques. Formation of disordered carbonaceous network in the implanted layers has been observed using Raman and UV-Visible spectroscopy. A sharp decline in band gap values (4.1 eV to 0.63 eV) with increase in implantation dose has been observed. This decrease in optical band gap has been correlated with the formation of disordered structures in the implanted layers of polycarbonate.

Structural and optical studies on selected web spinning spider silks

NASA Astrophysics Data System (ADS)

Karthikeyani, R.; Divya, A.; Mathavan, T.; Asath, R. Mohamed; Benial, A. Milton Franklin; Muthuchelian, K.

2017-01-01

This study investigates the structural and optical properties in the cribellate silk of the sheet web spider Stegodyphus sarasinorum Karsch (Eresidae) and the combined dragline, viscid silk of the orb-web spiders Argiope pulchella Thorell (Araneidae) and Nephila pilipes Fabricius (Nephilidae). X-ray diffraction (XRD), Fourier transform infra-red (FTIR), Ultraviolet-visible (UV-Vis) and fluorescence spectroscopic techniques were used to study these three spider silk species. X-ray diffraction data are consistent with the amorphous polymer network which is arising from the interaction of larger side chain amino acid contributions due to the poly-glycine rich sequences known to be present in the proteins of cribellate silk. The same amorphous polymer networks have been determined from the combined dragline and viscid silk of orb-web spiders. From FTIR spectra the results demonstrate that, cribellate silk of Stegodyphus sarasinorum, combined dragline viscid silk of Argiope pulchella and Nephila pilipes spider silks are showing protein peaks in the amide I, II and III regions. Further they proved that the functional groups present in the protein moieties are attributed to α-helical and side chain amino acid contributions. The optical properties of the obtained spider silks such as extinction coefficients, refractive index, real and imaginary dielectric constants and optical conductance were studied extensively from UV-Vis analysis. The important fluorescent amino acid tyrosine is present in the protein folding was investigated by using fluorescence spectroscopy. This research would explore the protein moieties present in the spider silks which were found to be associated with α-helix and side chain amino acid contributions than with β-sheet secondary structure and also the optical relationship between the three different spider silks are investigated. Successful spectroscopic knowledge of the internal protein structure and optical properties of the spider silks could permit industrial production of silk-based fibres with unique properties under benign conditions.

Correlation between structural and opto-electronic characteristics of crystalline Si microhole arrays for photonic light management

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sontheimer, Tobias, E-mail: tobias.sontheimer@helmholtz-berlin.de; Schnegg, Alexander; Lips, Klaus

2013-11-07

By employing electron paramagnetic resonance spectroscopy, transmission electron microscopy, and optical measurements, we systematically correlate the structural and optical properties with the deep-level defect characteristics of various tailored periodic Si microhole arrays, which are manufactured in an easily scalable and versatile process on nanoimprinted sol-gel coated glass. While tapered microhole arrays in a structured base layer are characterized by partly nanocrystalline features, poor electronic quality with a defect concentration of 10{sup 17} cm{sup −3} and a high optical sub-band gap absorption, planar polycrystalline Si layers perforated with periodic arrays of tapered microholes are composed of a compact crystalline structure and amore » defect concentration in the low 10{sup 16} cm{sup −3} regime. The low defect concentration is equivalent to the one in planar state-of-the-art solid phase crystallized Si films and correlates with a low optical sub-band gap absorption. By complementing the experimental characterization with 3-dimensional finite element simulations, we provide the basis for a computer-aided approach for the low-cost fabrication of novel high-quality structures on large areas featuring tailored opto-electronic properties.« less

Development of the α-IGZO/Ag/α-IGZO Triple-Layer Structure Films for the Application of Transparent Electrode

PubMed Central

Chen, Kun-Neng; Yang, Cheng-Fu; Wu, Chia-Ching; Chen, Yu-Hsin

2017-01-01

We investigated the structural, optical, and electrical properties of amorphous IGZO/silver/amorphous IGZO (α-IGZO/Ag/α-IGZO) triple-layer structures that were deposited at room temperature on Eagle XG glass and flexible polyethylene terephthalate substrates through the sputtering method. Thin Ag layers with different thicknesses were inserted between two IGZO layers to form a triple-layer structure. Ag was used because of its lower absorption and resistivity. Field emission scanning electron microscopy measurements of the triple-layer structures revealed that the thicknesses of the Ag layers ranged from 13 to 41 nm. The thickness of the Ag layer had a large effect on the electrical and optical properties of the electrodes. The optimum thickness of the Ag metal thin film could be evaluated according to the optical transmittance, electrical conductivity, and figure of merit of the electrode. This study demonstrates that the α-IGZO/Ag/α-IGZO triple-layer transparent electrode can be fabricated with low sheet resistance (4.2 Ω/□) and high optical transmittance (88.1%) at room temperature without postannealing processing on the deposited thin films. PMID:28772586

VLT observations of the two Fermi pulsars PSR J1357$-$6429 and PSR J1048$-$5832

DOE PAGES

Mignani, R. P.; Shearer, A.; De Luca, A.; ...

2011-09-07

Optical observations of pulsars are crucial to studying the neutron star properties from the structure and composition of the interior to the properties and geometry of the magnetosphere. Historically, X and γ-ray observations have paved the way to pulsar optical identifications. Furthermore, the launch of the Fermi Gamma-ray Space Telescope opened new perspectives in the optical-to-γ-ray studies of neutron stars with the detection of more than 80 γ-ray pulsars.

Three-dimensional fuse deposition modeling of tissue-simulating phantom for biomedical optical imaging

NASA Astrophysics Data System (ADS)

Dong, Erbao; Zhao, Zuhua; Wang, Minjie; Xie, Yanjun; Li, Shidi; Shao, Pengfei; Cheng, Liuquan; Xu, Ronald X.

2015-12-01

Biomedical optical devices are widely used for clinical detection of various tissue anomalies. However, optical measurements have limited accuracy and traceability, partially owing to the lack of effective calibration methods that simulate the actual tissue conditions. To facilitate standardized calibration and performance evaluation of medical optical devices, we develop a three-dimensional fuse deposition modeling (FDM) technique for freeform fabrication of tissue-simulating phantoms. The FDM system uses transparent gel wax as the base material, titanium dioxide (TiO2) powder as the scattering ingredient, and graphite powder as the absorption ingredient. The ingredients are preheated, mixed, and deposited at the designated ratios layer-by-layer to simulate tissue structural and optical heterogeneities. By printing the sections of human brain model based on magnetic resonance images, we demonstrate the capability for simulating tissue structural heterogeneities. By measuring optical properties of multilayered phantoms and comparing with numerical simulation, we demonstrate the feasibility for simulating tissue optical properties. By creating a rat head phantom with embedded vasculature, we demonstrate the potential for mimicking physiologic processes of a living system.

Crystal structure, electronic structure, and photoluminescent properties of SrMoO{sub 4}:Tb{sup 3+} phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Sung Wook; Moon, Byung Kee; Jeong, Jung Hyun, E-mail: jhjeong@pknu.ac.kr

2015-10-15

Highlights: • SrMoO{sub 4}:Tb{sup 3+} phosphor samples were synthesized at different temperatures. • The crystal and electronic structures, and luminescence properties were studied. • The excitation peak shifts to red with increasing the sintering temperature. • The luminescence mechanism of SrMoO{sub 4}:Tb{sup 3+} was suggested. - Abstract: The experimental and theoretical studies of the optical properties of SrMoO{sub 4}:Tb{sup 3+} phosphors were carried out. The structural, optical, and electronical properties of the phosphors were systematically studied. The phosphor samples were crystallized at different temperatures via a sol–gel method. Excitation spectra of SrMoO{sub 4}:Tb{sup 3+} powder samples exhibited gradual red shiftmore » and luminescent intensity changed with increasing the sintering temperature. Such spectral changes depend strongly on the crystallographic properties such as lattice parameters and crystallinity. The shift of the excitation spectra is mainly ascribed to the covalent bond interaction between Mo−O bonds. An energy band model was demonstrated to describe the luminescence mechanism in the material.« less

Effects of Langmuir-Blodgett-film gas sensors with integrated optical interferometers

NASA Astrophysics Data System (ADS)

Fushen, Chen; Yunqi, Liu; Yu, Xu; Qu, Liang

1996-10-01

Novel Langmuir-Blodgett-film toxic-gas sensors that have a Ti:LiNbO 3 integrated optical Mach-Zehnder interferometer structure are experimentally investigated. The gas-sensing properties of the sensors are obtained for NO 2, Cl2, NH3, and H2S by means of the detection of optical output changes. All the optical connections are made with optical fiber pigtails.

Application of spatially modulated near-infrared structured light to study changes in optical properties of mouse brain tissue during heatstress.

PubMed

Shaul, Oren; Fanrazi-Kahana, Michal; Meitav, Omri; Pinhasi, Gad A; Abookasis, David

2017-11-10

Heat stress (HS) is a medical emergency defined by abnormally elevated body temperature that causes biochemical, physiological, and hematological changes. The goal of the present research was to detect variations in optical properties (absorption, reduced scattering, and refractive index coefficients) of mouse brain tissue during HS by using near-infrared (NIR) spatial light modulation. NIR spatial patterns with different spatial phases were used to differentiate the effects of tissue scattering from those of absorption. Decoupling optical scattering from absorption enabled the quantification of a tissue's chemical constituents (related to light absorption) and structural properties (related to light scattering). Technically, structured light patterns at low and high spatial frequencies of six wavelengths ranging between 690 and 970 nm were projected onto the mouse scalp surface while diffuse reflected light was recorded by a CCD camera positioned perpendicular to the mouse scalp. Concurrently to pattern projection, brain temperature was measured with a thermal camera positioned slightly off angle from the mouse head while core body temperature was monitored by thermocouple probe. Data analysis demonstrated variations from baseline measurements in a battery of intrinsic brain properties following HS.

Optical properties and mechanisms in Cr3+, Bi3+-codoped oxide-based spinel nanoparticles

NASA Astrophysics Data System (ADS)

Pellerin, Morgane; Coelho-Diogo, Cristina; Bonhomme, Christian; Touatib, Nadia; Binet, Laurent; Gourier, Didier; Ueda, Jumpei; Tanabe, Setsuhisa; Viana, Bruno; Chanéac, Corinne

2017-02-01

At the nanoscale, the ZnGa2O4 spinel doped with chromium (III) is an interesting material for in vivo optical imaging due to its bright red persistent luminescence after UV and visible excitation. Moreover its persistent luminescent properties can be improved with the incorporation of bismuth (III) as a co-dopant without any structure changes. The nanoparticles are synthesized by soft chemistry using microwave heating in aqueous media. These very small sized nanophosphors (around 10 nm) present interesting long lasting persistent luminescence after annealing at 1000°C and they can be excited both under UV and under visible LED excitation. In this work we try to understand the mechanisms of the persistent luminescent properties of such nanomaterials. Thermoluminescence is performed to investigate trapping and detrapping processes as well as trap distribution. The chromium local environment is studied by Electron Paramagnetic Resonance. 71Ga Nuclear Magnetic Resonance is used to get information on the gallium ions repartition (tetrahedral or octahedral site) in the structure. Comparison of optical properties versus local structure increases the understanding of the persistent luminescence mechanism and gives insights to the new modalities for their use as nanoprobes for in vivo imaging.

Morphological, structural and optical properties of MEH-PPV: PC70BM nanocomposite film

NASA Astrophysics Data System (ADS)

Mhamdi, Asya; Sweii, Fatma ben Slama; Saidi, Hamza; Saidi, Faouzi; Bouazizi, Abdelaziz

2018-05-01

In this report, the influence of annealing temperature and spin coating speed on the structural and morphological properties of a blend of poly (2-methoxy-5-(2-ethyl-oxy)-p-phenylene-vinylene) (MEH-PPV) and [6-6]-phenyl-C71-butyric acid methyl ester (PC70BM) layer has been investigated. The photoactive layer (MEH-PPV: PC70BM) was deposited on ZnO film deposited on top of indium tin oxide (ITO) substrate by spin-coating. The effect of spin coating speed via atomic force microscope (AFM) leads to conclude that high speed is favorable for a good homogeneity of the film surface and good aggregates dispersion. The optimized structure was studied by varying the annealing temperatures using X-ray diffraction (XRD). The XRD analysis indicates that annealing treatment promoted the ordered aggregation and crystallization of MEH-PPV: PC70BM films. Indeed, the blend ratio effect on the optical properties of MEH-PPV: PC70BM thin film was investigated. While, the effect of incorporation of PC70BM on the optical properties was studied using UV-Vis and photoluminescence (PL) measurement. We conclude that MEH-PPV: PC70BM (1:3) film leads to high charge transfer rate.

Influence of amines as surfactant on the optical, thermal, and structural properties of nanostructured ZnO

NASA Astrophysics Data System (ADS)

Sehgal, Preeti; Narula, A. K.

2015-06-01

Zinc oxide nanoparticles were synthesized by precipitation method using triethanolamine (TEA) and hexamine (HA) as capping agents, and their effects on the optical, thermal, and morphological properties were analyzed. We have also analyzed the role of solvents on the aforementioned properties of ZnO nanoparticles. The optical properties of capped zinc oxide nanoparticles were investigated by UV-visible and fluorescent techniques. The HA@ZnO and TEA@ZnO that showed blueshift in comparison with ZnO without surfactant revealed the role of surfactant in reducing the trap sites by forming defect-free nanoparticles. TG-DTA curves indicated that optimum annealing temperature for ZnO nanoparticles was in the range of 360-469 °C depending upon the surfactant and solvent; no weight loss was observed above 469 °C. Synthesized ZnO nanoparticles had pure wurtzite structure as elucidated by X-ray diffraction studies (XRD). Scanning electron microscope revealed that the ZnO synthesized in isopropyl alcohol had spherical morphology, whereas ZnO nanoparticles synthesized in methanol had agglomerate sheet-like structure. The average size of the nanocrystal was estimated around 85-169 nm for ZnO.

Study of nanoparticles TiO2 thin films on p-type silicon substrate using different alcoholic solvents

NASA Astrophysics Data System (ADS)

Muaz, A. K. M.; Hashim, U.; Arshad, M. K. Md.; Ruslinda, A. R.; Ayub, R. M.; Gopinath, Subash C. B.; Voon, C. H.; Liu, Wei-Wen; Foo, K. L.

2016-07-01

In this paper, sol-gel method spin coating technique is adopted to prepare nanoparticles titanium dioxide (TiO2) thin films. The prepared TiO2 sol was synthesized using titanium butoxide act as a precursor and subjected to deposited on the p-type silicon oxide (p-SiO2) and glass slide substrates under room temperature. The effect of different alcoholic solvents of methanol and ethanol on the structural, morphological, optical and electrical properties were systematically investigated. The coated TiO2 thin films were annealed in furnace at 773 K for 1 h. The structural properties of the TiO2 films were examined with X-ray Diffraction (XRD). From the XRD analysis, both solvents showing good crystallinity with anatase phase were the predominant structure. Atomic Force Microscopy (AFM) was employed to study the morphological of the thin films. The optical properties were investigated by Ultraviolet-visible (UV-Vis) spectroscopy were found that ethanol as a solvent give a higher optical transmittance if compare to the methanol solvent. The electrical properties of the nanoparticles TiO2 thin films were measured using two-point-probe technique.

Structural and optical properties of furfurylidenemalononitrile thin films

NASA Astrophysics Data System (ADS)

Ali, H. A. M.

2013-03-01

Thin films of furfurylidenemalononitrile (FMN) were deposited on different substrates at room temperature by thermal evaporation technique under a high vacuum. The structure of the powder was confirmed by Fourier transformation infrared (FTIR) technique. The unit cell dimensions were determined from X-ray diffraction (XRD) studies. The optical properties were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence of light in the wavelength range from 200 to 2500 nm. The refractive index (n), the absorption index (k) and the absorption coefficient (α) were calculated. The analysis of the spectral behavior of the absorption coefficient in the absorption region revealed an indirect allowed transition. The refractive index dispersion was analyzed using the single oscillator model. Some dispersion parameters were estimated. Complex dielectric function and optical conductivity were determined. The influence of the irradiation with high-energy X-rays (6 MeV) on the studied properties was also investigated.

Process-Parameter-Dependent Optical and Structural Properties of ZrO2MgO Mixed-Composite Films Evaporated from the solid Solution

NASA Technical Reports Server (NTRS)

Sahoo, N. K.; Shapiro, A. P.

1998-01-01

The process-parameter-dependent optical and structural properties of ZrO2MgO mixed-composite material have been investigated. Optical properties were derived from spectrophotometric measurements. By use of atomic force microscopy, x-ray diffraction analysis, and energy-dispersive x-ray (EDX) analysis, the surface morphology, grain size distributions, crystallographic phases, and process-dependent material composition of films have been investigated. EDX analysis made evident the correlation between the oxygen enrichment in the films prepared at a high level of oxygen pressure and the very low refractive index. Since oxygen pressure can be dynamically varied during a deposition process, coatings constructed of suitable mixed-composite thin films can benefit from continuous modulation of the index of refraction. A step modulation approach is used to develop various multilayer-equivalent thin-film devices.

Optical stress generator and detector

DOEpatents

Maris, Humphrey J.; Stoner, Robert J

2001-01-01

Disclosed is a system for the characterization of thin films and interfaces between thin films through measurements of their mechanical and thermal properties. In the system light is absorbed in a thin film or in a structure made up of several thin films, and the change in optical transmission or reflection is measured and analyzed. The change in reflection or transmission is used to give information about the ultrasonic waves that are produced in the structure. The information that is obtained from the use of the measurement methods and apparatus of this invention can include: (a) a determination of the thickness of thin films with a speed and accuracy that is improved compared to earlier methods; (b) a determination of the thermal, elastic, and optical properties of thin films; (c) a determination of the stress in thin films; and (d) a characterization of the properties of interfaces, including the presence of roughness and defects.

Optical stress generator and detector

DOEpatents

Maris, Humphrey J.; Stoner, Robert J.

1998-01-01

Disclosed is a system for the characterization of thin films and interfaces between thin films through measurements of their mechanical and thermal properties. In the system light is absorbed in a thin film or in a structure made up of several thin films, and the change in optical transmission or reflection is measured and analyzed. The change in reflection or transmission is used to give information about the ultrasonic waves that are produced in the structure. The information that is obtained from the use of the measurement methods and apparatus of this invention can include: (a) a determination of the thickness of thin films with a speed and accuracy that is improved compared to earlier methods; (b) a determination of the thermal, elastic, and optical properties of thin films; (c) a determination of the stress in thin films; and (d) a characterization of the properties of interfaces, including the presence of roughness and defects.

Optical stress generator and detector

DOEpatents

Maris, H.J.; Stoner, R.J.

1998-05-05

Disclosed is a system for the characterization of thin films and interfaces between thin films through measurements of their mechanical and thermal properties. In the system light is absorbed in a thin film or in a structure made up of several thin films, and the change in optical transmission or reflection is measured and analyzed. The change in reflection or transmission is used to give information about the ultrasonic waves that are produced in the structure. The information that is obtained from the use of the measurement methods and apparatus of this invention can include: (a) a determination of the thickness of thin films with a speed and accuracy that is improved compared to earlier methods; (b) a determination of the thermal, elastic, and optical properties of thin films; (c) a determination of the stress in thin films; and (d) a characterization of the properties of interfaces, including the presence of roughness and defects. 32 figs.

Optical stress generator and detector

DOEpatents

Maris, Humphrey J.; Stoner, Robert J

2002-01-01

Disclosed is a system for the characterization of thin films and interfaces between thin films through measurements of their mechanical and thermal properties. In the system light is absorbed in a thin film or in a structure made up of several thin films, and the change in optical transmission or reflection is measured and analyzed. The change in reflection or transmission is used to give information about the ultrasonic waves that are produced in the structure. The information that is obtained from the use of the measurement methods and apparatus of this invention can include: (a) a determination of the thickness of thin films with a speed and accuracy that is improved compared to earlier methods; (b) a determination of the thermal, elastic, and optical properties of thin films; (c) a determination of the stress in thin films; and (d) a characterization of the properties of interfaces, including the presence of roughness and defects.

Optical stress generator and detector

DOEpatents

Maris, Humphrey J.; Stoner, Robert J

1999-01-01

Disclosed is a system for the characterization of thin films and interfaces between thin films through measurements of their mechanical and thermal properties. In the system light is absorbed in a thin film or in a structure made up of several thin films, and the change in optical transmission or reflection is measured and analyzed. The change in reflection or transmission is used to give information about the ultrasonic waves that are produced in the structure. The information that is obtained from the use of the measurement methods and apparatus of this invention can include: (a) a determination of the thickness of thin films with a speed and accuracy that is improved compared to earlier methods; (b) a determination of the thermal, elastic, and optical properties of thin films; (c) a determination of the stress in thin films; and (d) a characterization of the properties of interfaces, including the presence of roughness and defects.

Ab-initio calculation of electronic structure and optical properties of AB-stacked bilayer α-graphyne

NASA Astrophysics Data System (ADS)

Behzad, Somayeh

2016-09-01

Monolayer α-graphyne is a new two-dimensional carbon allotrope with many special features. In this work the electronic properties of AA- and AB-stacked bilayers of this material and then the optical properties are studied, using first principle plane wave method. The electronic spectrum has two Dirac cones for AA stacked bilayer α-graphyne. For AB-stacked bilayer, the interlayer interaction changes the linear bands into parabolic bands. The optical spectra of the most stable AB-stacked bilayer closely resemble to that of the monolayer, except for small shifts of peak positions and increasing of their intensity. For AB-stacked bilayer, a pronounced peak has been found at low energies under the perpendicular polarization. This peak can be clearly ascribed to the transitions at the Dirac point as a result of the small degeneracy lift in the band structure.

Slow-light transmission with high group index and large normalized delay bandwidth product through successive defect rods on intrinsic photonic crystal waveguide

NASA Astrophysics Data System (ADS)

Elshahat, Sayed; Khan, Karim; Yadav, Ashish; Bibbò, Luigi; Ouyang, Zhengbiao

2018-07-01

We proposed a strategy with successive cavities as energy reservoirs of electromagnetic energy and light-speed reducers introduced in the first and second rows of rods on the walls of an intrinsic photonic crystal waveguide (PCW) for slow-light transmission in the PCW concerning applications for optical communication, optical computation and optical signal processing. Subsequently, plane-wave expansion method (PWE) is used for studying slow-light properties and finite-difference time-domain (FDTD) method to demonstrate the slow-light propagating property of our proposed structure. We obtained group index as exceedingly large as 6123 with normalized delay bandwidth product (NDBP) as high as 0.48. We designed a facile but more generalized structure that may provide a vital theoretical basis for further enhancing the storage capacity properties of slow light with wideband and high NDBP.

Theoretical study of optical properties of anti phase domains in GaP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tea, E., E-mail: etea.contact@gmail.com; FOTON INSA-Rennes; Vidal, J.

III-V/Si heterostructures are currently investigated for silicon photonics and solar energy conversion. In particular, dilute nitride alloy GaAsPN grown on a GaP/Si platform exhibits lattice match with Si and an optimal band gap configuration for tandem solar cell devices. However, monolithic “coherent” growth of the GaP thin layer on Si suffers from the nucleation of extended structural defects, which can hamper device operation as well as the GaP/Si interface level and through their propagation inside the overall heterostructure. However, the effect of such structural defects on optical and transport properties is actually not well understood in details. In this letter,more » we investigate the anti phase domains defect (also called inversion domains) by means of ab initio calculations giving insights into the alteration of optical and transport properties of GaP due to the defective GaP/Si interface.« less

Optical and electrical properties of mechanochemically synthesized nanocrystalline delafossite CuAlO2.

PubMed

Prakash, T; Prasad, K Padma; Ramasamy, S; Murty, B S

2008-08-01

Nanocrystalline p-type semiconductor copper aluminum oxide (CuAlO2) has been synthesized by mechanical alloying using freshly prepared Cu2O and alpha-AlO2O3 nanocrystals in toluene medium. A study on structural property performed with different alloying and post annealing durations, by X-ray diffraction (XRD) reveals the formation of single phase with average crystallite size approximately 45 nm. Optical absorbance onset at 364.5 nm confirms its wide band gap nature (E(g) = 3.4 eV) and the fluorescence emission behaviour (390 nm) confirms its direct band type transition. The activation energy for electrical conduction has been calculated by Arrhenius plots using impedance measurement. Both grain and grain boundary conductivity takes place with almost equal activation energies of approximately 0.45 eV. The paper discusses synthesis, structural, optical and electrical properties of delafossite CuAlO2 in detail.

Effects of various applied voltages on physical properties of TiO2 nanotubes by anodization method

NASA Astrophysics Data System (ADS)

Hoseinzadeh, T.; Ghorannevis, Z.; Ghoranneviss, M.; Sari, A. H.; Salem, M. K.

2017-09-01

Three steps anodization process is used to synthesize highly ordered and uniform multilayered titanium oxide (TiO2) nanotubes and effect of different anodization voltages are studied on their physical properties such as structural, morphological and optical. The crystalized structure of the synthesized tubes is investigated by X-ray diffractometer analysis. To study the morphology of the tubes, field emission scanning electron microscopy is used, which showed that the wall thicknesses and the diameters of the tubes are affected by the different anodization voltages. Moreover, optical studies performed by diffuse reflection spectra suggested that band gap of the TiO2 nanotubes are also changed by applying different anodization voltages. In this study using physical investigations, an optimum anodization voltage is obtained to synthesize the uniform crystalized TiO2 nanotubes with suitable diameter, wall thickness and optical properties.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dincă, Mircea; Léonard, François

Metal–organic frameworks (MOFs), with their crystalline nanoporous three-dimensional structures, have emerged as unique multifunctional materials that combine high porosity with catalytic, photophysical, or other properties to reveal new fundamental science and applications. Because MOFs are composed of organic molecules linking metal centers in ways that are not usually conducive to the formation of free-charge carriers or low-energy charge-transport pathways, they are typically insulators. Accordingly, applications so far have harnessed the unique structural properties and porosity of MOFs, which depend only to a small extent on the ability to manipulate their electronic structure. An exciting new area has emerged due tomore » the recent demonstration of MOFs with controlled electronic and optical properties, which is enabling new fundamental science and opens up the possibility of applications in electronics and photonics. This article presents an overview of the fundamental science issues related to controlling electronic and optical properties of MOFs, and how research groups worldwide have been exploring such properties for electronics, thermoelectrics, photophysics, and charge storage.« less

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

NASA Astrophysics Data System (ADS)

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.

Dual-mode MOS SOI nanoscale transistor serving as a building block for optical communication between blocks

NASA Astrophysics Data System (ADS)

Bendayan, Michael; Sabo, Roi; Zolberg, Roee; Mandelbaum, Yaakov; Chelly, Avraham; Karsenty, Avi

2017-02-01

We developed a new type of silicon MOSFET Quantum Well transistor, coupling both electronic and optical properties which should overcome the indirect silicon bandgap constraint, and serve as a future light emitting device in the range 0.8-2μm, as part of a new building block in integrated circuits allowing ultra-high speed processors. Such Quantum Well structure enables discrete energy levels for light recombination. Model and simulations of both optical and electric properties are presented pointing out the influence of the channel thickness and the drain voltage on the optical emission spectrum.

Tunable optical and excitonic properties of phosphorene via oxidation

NASA Astrophysics Data System (ADS)

Sadki, S.; Drissi, L. B.

2018-06-01

The optical properties and excitonic wave function of phosphorene oxides (PO) are studied using the first principle many-body Green function and the Bethe–Salpeter equation formalism. In this work, the optical properties are determined using ab initio calculations of the dielectric function. At the long wavelength limit q of EM wave (i.e. ), the dielectric function, the absorption spectrum, the lectivity, the electron energy loss spectra (EELS) and the wave function are calculated. The results show an excitonic binding energy of 818 meV with a bright exciton located in the armchair direction in pristine phosphorene. For PO, the arrangement of the oxygen atoms significantly influences the optical properties. In particular, the absorption spectrum is extended along the solar spectrum, with a high absorption coefficient observed in the dangling structures. The maximum lectivity values are observed for the high energies of the light spectrum. Moreover, the first EELS peak is located in the visible region in all the structures except for one configuration that exhibits the same behavior as pure phosphorene. Finally, the exciton effect reveals that all PO conformers have a dark exciton state, which is suitable for long-lived applications.

Molecular Organization Induced Anisotropic Properties of Perylene - Silica Hybrid Nanoparticles.

PubMed

Sriramulu, Deepa; Turaga, Shuvan Prashant; Bettiol, Andrew Anthony; Valiyaveettil, Suresh

2017-08-10

Optically active silica nanoparticles are interesting owing to high stability and easy accessibility. Unlike previous reports on dye loaded silica particles, here we address an important question on how optical properties are dependent on the aggregation-induced segregation of perylene molecules inside and outside the silica nanoparticles. Three differentially functionalized fluorescent perylene - silica hybrid nanoparticles are prepared from appropriate ratios of perylene derivatives and tetraethyl orthosilicate (TEOS) and investigated the structure property correlation (P-ST, P-NP and P-SF). The particles differ from each other on the distribution, organization and intermolecular interaction of perylene inside or outside the silica matrix. Structure and morphology of all hybrid nanoparticles were characterized using a range of techniques such as electron microscope, optical spectroscopic measurements and thermal analysis. The organizations of perylene in three different silica nanoparticles were explored using steady-state fluorescence, fluorescence anisotropy, lifetime measurements and solid state polarized spectroscopic studies. The interactions and changes in optical properties of the silica nanoparticles in presence of different amines were tested and quantified both in solution and in vapor phase using fluorescence quenching studies. The synthesized materials can be regenerated after washing with water and reused for sensing of amines.

Numerical simulation studies for optical properties of biomaterials

NASA Astrophysics Data System (ADS)

Krasnikov, I.; Seteikin, A.

2016-11-01

Biophotonics involves understanding how light interacts with biological matter, from molecules and cells, to tissues and even whole organisms. Light can be used to probe biomolecular events, such as gene expression and protein-protein interaction, with impressively high sensitivity and specificity. The spatial and temporal distribution of biochemical constituents can also be visualized with light and, thus, the corresponding physiological dynamics in living cells, tissues, and organisms in real time. Computer-based Monte Carlo (MC) models of light transport in turbid media take a different approach. In this paper, the optical and structural properties of biomaterials discussed. We explain the numerical simulationmethod used for studying the optical properties of biomaterials. Applications of the Monte-Carlo method in photodynamic therapy, skin tissue optics, and bioimaging described.

Quasiparticle and optical properties of strained stanene and stanane.

PubMed

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.

Structural, optical, magnetic and electrical properties of hematite (α-Fe2O3) nanoparticles synthesized by two methods: polyol and precipitation

NASA Astrophysics Data System (ADS)

Mansour, Houda; Letifi, Hanen; Bargougui, Radhouane; De Almeida-Didry, Sonia; Negulescu, Beatrice; Autret-Lambert, Cécile; Gadri, Abdellatif; Ammar, Salah

2017-12-01

Hematite (α-Fe2O3) nanoparticles have been successfully synthesized via two methods: (1) polyol and (2) precipitation in water. The influence of synthesis methods on the crystalline structure, morphological, optical, magnetic and electrical properties were investigated using X-ray diffraction, RAMAN spectroscopy, scanning electron microscopy, transmission electron microscopy, UV-visible diffuse reflectance spectroscopy (UV-vis DRS), superconducting quantum interference device and impedance spectroscopy. The structural properties showed that the obtained hematite α-Fe2O3 nanoparticles with two preparation methods exhibit hexagonal phase with high crystallinity and high-phase stability at room temperature. It was found that the average hematite nanoparticle size is estimated to be 36.86 nm for the sample synthesized by precipitation and 54.14 nm for the sample synthesized by polyol. Moreover, the optical properties showed that the band gap energy value of α-Fe2O3 synthesized by precipitation (2.07 eV) was higher than that of α-Fe2O3 synthesized by polyol (1.97 eV) and they showed a red shift to the visible region. Furthermore, the measurements of magnetic properties indicated a magnetization loop typical of ferromagnetic systems at room temperature. Measurements of electrical properties show higher dielectric permittivity (5.64 × 103) and relaxation phenomenon for α-Fe2O3 issued from the precipitation method than the other sample.

Effects of various deposition times and RF powers on CdTe thin film growth using magnetron sputtering

NASA Astrophysics Data System (ADS)

Ghorannevis, Z.; Akbarnejad, E.; Ghoranneviss, M.

2016-09-01

Cadmium telluride (CdTe) is a p-type II-VI compound semiconductor, which is an active component for producing photovoltaic solar cells in the form of thin films, due to its desirable physical properties. In this study, CdTe film was deposited using the radio frequency (RF) magnetron sputtering system onto a glass substrate. To improve the properties of the CdTe film, effects of two experimental parameters of deposition time and RF power were investigated on the physical properties of the CdTe films. X-ray Diffraction (XRD), atomic force microscopy (AFM) and spectrophotometer were used to study the structural, morphological and optical properties of the CdTe samples grown at different experimental conditions, respectively. Our results suggest that film properties strongly depend on the experimental parameters and by optimizing these parameters, it is possible to tune the desired structural, morphological and optical properties. From XRD data, it is found that increasing the deposition time and RF power leads to increasing the crystallinity as well as the crystal sizes of the grown film, and all the films represent zinc blende cubic structure. Roughness values given from AFM images suggest increasing the roughness of the CdTe films by increasing the RF power and deposition times. Finally, optical investigations reveal increasing the film band gaps by increasing the RF power and the deposition time.

Optical properties of a scorpion (Centruroides limpidus)

NASA Astrophysics Data System (ADS)

Ullrich, Bruno; Duckworth, Robyn M.; Singh, Akhilesh K.; Barik, Puspendu; Mejía-Villanueva, Vicente O.; Garcia-Pérez, Alberto C.

2016-04-01

Scorpions, elusive by nature, tend to appear nocturnally and are usually not appreciated when encountered. The exoskeleton is capable of fluorescing allowing for their detection at night in order to prevent undesirable encounters. The specificity of their fluorescing suggests specialized optical features. However, despite the blue-green fluorescence, to the best of our knowledge, no further results have been published on the optical properties of scorpions. Their exoskeletal structure whose versatility provides them protection, camouflage, and flexibility has not been studied under laser excitation and monochromatic light. The experiments reveal the nonlinear optical properties, infrared photoluminescence, and photoconductivity of the epicuticle of scorpions, demonstrating that the scorpion’s outer-covering is a prototype of a semiconducting inherently integrated multifunctional polymeric film with appealing potential applications such as optical logics, photonic frequency converters, novel multiplexers handling electronic and photonic inputs, and lasers.

Extraordinary optical transmission through wedge-shape metallic slits array embedded with rectangular cavities

NASA Astrophysics Data System (ADS)

Qi, Yunping; Zhang, Xuewei; Hu, Yue; Nan, Xianghong; Wang, Xiangxian

2017-10-01

The non-resonantly enhanced optical transmission phenomenon of sub-wavelength metallic slits on a thin film is significant for broadband light integrated devices. In order to improve the EOT characteristics of sub-wavelength metallic slits further more, in this paper, wedge-shape metallic slits array embedded with rectangular cavities structure is proposed and its transmission properties are investigated using the finite element method. The results show that wedgeshape metallic slits array can achieve higher transmission compared with straight slits array embedded with rectangular cavities and the light is strongly localized and enhanced at the slit exits. We describe the phenomenon with a transmission line model. The width of entrance of the slit influences the transmission property: the transmittance can be 94%, after optimizing the structure parameters, with the widths 150nm and 30nm at the entrance and exit of the slit, respectively. The thickness of metal film influences the transmission peak position and transmission rate: when the increase of the thickness of the metal film, the transmittance increases and the transmission peak is red-shift, however, the law of long wavelength range is opposite. In addition, the effects of structural period of wedge-shaped slits embedded with rectangular cavities structure on the transmission property are also studied. These results would be helpful for optical signal transmission and the design of near field optical conductor devices with higher transmission capability.

The properties of electromagnetic responses and optical modulation in terahertz metamaterials

NASA Astrophysics Data System (ADS)

Chen, Wei; Shi, Yulei; Wang, Wei; Zhou, Qingli; Zhang, Cunlin

2016-11-01

Metamaterials with subwavelength structural features show unique electromagnetic responses that are unattainable with natural materials. Recently, the research on these artificial materials has been pushed forward to the terahertz (THz) region because of potential applications in biological fingerprinting, security imaging, and high frequency magnetic and electric resonant devices. Furthermore, active control of their properties could further facilitate and open up new applications in terms of modulation and switching. In our work, we will first present our studies of dipole arrays at terahertz frequencies. Then in experimental and theoretical studies of terahertz subwavelength L-shaped structure, we proposed an unusual-mode current resonance responsible for low-frequency characteristic dip in transmission spectra. Comparing spectral properties of our designed simplified structures with that of split-ring resonators, we attribute this unusual mode to the resonance coupling and splitting under the broken symmetry of the structure. Finally, we use optical pump-terahertz probe method to investigate the spectral and dynamic behaviour of optical modulation in the split-ring resonators. We have observed the blue-shift and band broadening in the spectral changes of transmission under optical excitation at different delay times. The calculated surface currents using finite difference time domain simulation are presented to characterize these resonances, and the blue-shift can be explained by the changed refractive index and conductivity in the photoexcited semiconductor substrate.

Pathway to oxide photovoltaics via band-structure engineering of SnO

DOE PAGES

Peng, Haowei; Bikowski, Andre; Zakutayev, Andriy; ...

2016-10-04

All-oxide photovoltaics could open rapidly scalable manufacturing routes, if only oxide materials with suitable electronic and optical properties were developed. SnO has exceptional doping and transport properties among oxides, but suffers from a strongly indirect band gap. Here, we address this shortcoming by band-structure engineering through isovalent but heterostructural alloying with divalent cations (Mg, Ca, Sr, and Zn). Furthermore, using first-principles calculations, we show that suitable band gaps and optical properties close to that of direct semiconductors are achievable, while the comparatively small effective masses are preserved in the alloys. Initial thin film synthesis and characterization support the feasibility ofmore » the approach.« less

Structure and optical properties of silica-supported Ag-Au nanoparticles.

PubMed

Barreca, Davide; Gasparotto, Alberto; Maragno, Cinzia; Tondello, Eugenio; Gialanella, Stefano

2007-07-01

Bimetallic Ag-Au nanoparticles are synthesized by sequential deposition of Au and Ag on amorphous silica by Radio Frequency (RF)-sputtering under mild conditions. Specimens are thoroughly characterized by a multi-technique approach, aimed at investigating the system properties as a function of the Ag/Au content, as well as the evolution induced by ex-situ annealing under inert (N2) or reducing (4% H2/N2) atmospheres. The obtained results demonstrate the possibility to obtain Ag-Au alloyed nanoparticles with controllable size, shape, structure, and dispersion under mild conditions, so that the optical properties can be finely tuned as a function of the synthesis and thermal treatment conditions.

Electrical and optical transport properties of single layer WSe2

NASA Astrophysics Data System (ADS)

Tahir, M.

2018-03-01

The electronic properties of single layer WSe2 are distinct from the famous graphene due to strong spin orbit coupling, a huge band gap and an anisotropic lifting of the degeneracy of the valley degree of freedom under Zeeman field. In this work, band structure of the monolayer WSe2 is evaluated in the presence of spin and valley Zeeman fields to study the electrical and optical transport properties. Using Kubo formalism, an explicit expression for the electrical Hall conductivity is examined at finite temperatures. The electrical longitudinal conductivity is also evaluated. Further, the longitudinal and Hall optical conductivities are analyzed. It is observed that the contributions of the spin-up and spin-down states to the power absorption spectrum depend on the valley index. The numerical results exhibit absorption peaks as a function of photon energy, ℏ ω, in the range ∼ 1.5 -2 eV. Also, the optical response lies in the visible frequency range in contrast to the conventional two-dimensional electron gas or graphene where the response is limited to terahertz regime. This ability to isolate carriers in spin-valley coupled structures may make WSe2 a promising candidate for future spintronics, valleytronics and optical devices.

Tungsten Oxide Photonic Crystals as Optical Transducer for Gas Sensing.

PubMed

Amrehn, Sabrina; Wu, Xia; Wagner, Thorsten

2018-01-26

Some metal oxide semiconductors, such as tungsten trioxide or tin dioxide, are well-known as resistive transducers for gas sensing and offer high sensitivities down to the part per billion level. Electrical signal read-out, however, limits the information obtained on the electronic properties of metal oxides to a certain frequency range and its application because of the required electrical contacts. Therefore, a novel approach for building an optical transducer for gas reactions utilizing metal oxide photonic crystals is presented here. By the rational design of the structure and composition it is possible to synthesize a functional material which allows one to obtain insight into its electronic properties in the optical frequency range with simple experimental measures. The concept is demonstrated by tungsten trioxide inverse opal structure as optical transducer material for hydrogen sensing. The sensing behavior is analyzed in a temperature range from room temperature to 500 °C and in a wide hydrogen concentration range (3000 ppm to 10%). The sensing mechanism is mainly the refractive index change resulting from hydrogen intercalation in tungsten trioxide, but the back reaction has also impact on the optical properties of this system. Detailed chemical reaction studies provide suggestions for specific sensing conditions.

Structure and properties of fixed joints formed by ultrasonic-assisted friction-stir welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fortuna, S. V., E-mail: s-fortuna@ispms.ru; Ivanov, K. V., E-mail: ikv@ispms.ru; Eliseev, A. A., E-mail: alan@ispms.ru

2015-10-27

This paper deals with structure and properties of aluminum alloy 7475 and its joints obtained by friction stir welding including under ultrasonic action. Microhardness measurements show that ultrasonic action increases strength properties of the joints. Optical and transmission electron microscopy reveals that this effect is related to the precipitation of tertiary coherent S-and T-phase particles.

Liquid-crystals electro-optic modulator based on electrohydrodynamic effects.

PubMed

Muriel, M A; Martin-Pereda, J A

1980-11-01

A new method of light modulation is reported. This method is based on the electro-optical properties of nematic materials and on the use of a new wedge structure. The advantages of this structure are the possibility of modulating nonpolarized light and the improved signal-to-noise ratio. The highest modulating frequency obtained is 25 kHz.

Structural and optical modification in 4H-SiC following 30 keV silver ion irradiation

NASA Astrophysics Data System (ADS)

Kaushik, Priya Darshni; Aziz, Anver; Siddiqui, Azher M.; Lakshmi, G. B. V. S.; Syväjärvi, Mikael; Yakimova, Rositsa; Yazdi, G. Reza

2018-05-01

The market of high power, high frequency and high temperature based electronic devices is captured by SiC due to its superior properties like high thermal conductivity and high sublimation temperature and also due to the limitation of silicon based electronics in this area. There is a need to investigate effect of ion irradiation on SiC due to its application in outer space as outer space is surrounded both by low and high energy ion irradiations. In this work, effect of low energy ion irradiation on structural and optical property of 4H-SiC is investigated. ATR-FTIR is used to study structural modification and UV-Visible spectroscopy is used to study optical modifications in 4H-SiC following 30 keV Ag ion irradiation. FTIR showed decrease in bond density of SiC along the ion path (track) due to the creation of point defects. UV-Visible absorption spectra showed decrease in optical band gap from 3.26 eV to 2.9 eV. The study showed degradation of SiC crystallity and change in optical band gap following low energy ion irradiation and should be addressed while fabricationg devices based on SiC for outer space application. Additionally, this study provides a platform for introducing structural and optical modification in 4H-SiC using ion beam technology in a controlled manner.

LASERS IN MEDICINE: Structure of matrices for the transformation of laser radiation by biofractals

NASA Astrophysics Data System (ADS)

Angel'skii, O. V.; Ushenko, A. G.; Arkhelyuk, A. D.; Ermolenko, S. B.; Burkovets, D. N.

1999-12-01

The changes in the state of polarisation of laser radiation transformed by biofractal objects are examined. The orientational angular structure of the matrix elements of the operator representing the optical properties of biofractals with different morphological structures (mineralised collagen fibres and myosin bundles) is investigated. An optical model for the description of fractal laser fields under the conditions of single light scattering is proposed.

Comprehensive design of omnidirectional high-performance perovskite solar cells

PubMed Central

Zhang, Yutao; Xuan, Yimin

2016-01-01

The comprehensive design approach is established with coupled optical-electrical simulation for perovskite-based solar cell, which emerged as one of the most promising competitors to silicon solar cell for its low-cost fabrication and high PCE. The selection of structured surface, effect of geometry parameters, incident angle-dependence and polarization-sensitivity are considered in the simulation. The optical modeling is performed via the finite-difference time-domain method whilst the electrical properties are obtained by solving the coupled nonlinear equations of Poisson, continuity, and drift-diffusion equations. The optical and electrical performances of five different structured surfaces are compared to select a best structured surface for perovskite solar cell. The effects of the geometry parameters on the optical and electrical properties of the perovskite cell are analyzed. The results indicate that the light harvesting is obviously enhanced by the structured surface. The electrical performance can be remarkably improved due to the enhanced light harvesting of the designed best structured surface. The angle-dependence for s- and p-polarizations is investigated. The structured surface exhibits omnidirectional behavior and favorable polarization-insensitive feature within a wide incident angle range. Such a comprehensive design approach can highlight the potential of perovskite cell for power conversion in the full daylight. PMID:27405419

Comprehensive design of omnidirectional high-performance perovskite solar cells.

PubMed

Zhang, Yutao; Xuan, Yimin

2016-07-13

The comprehensive design approach is established with coupled optical-electrical simulation for perovskite-based solar cell, which emerged as one of the most promising competitors to silicon solar cell for its low-cost fabrication and high PCE. The selection of structured surface, effect of geometry parameters, incident angle-dependence and polarization-sensitivity are considered in the simulation. The optical modeling is performed via the finite-difference time-domain method whilst the electrical properties are obtained by solving the coupled nonlinear equations of Poisson, continuity, and drift-diffusion equations. The optical and electrical performances of five different structured surfaces are compared to select a best structured surface for perovskite solar cell. The effects of the geometry parameters on the optical and electrical properties of the perovskite cell are analyzed. The results indicate that the light harvesting is obviously enhanced by the structured surface. The electrical performance can be remarkably improved due to the enhanced light harvesting of the designed best structured surface. The angle-dependence for s- and p-polarizations is investigated. The structured surface exhibits omnidirectional behavior and favorable polarization-insensitive feature within a wide incident angle range. Such a comprehensive design approach can highlight the potential of perovskite cell for power conversion in the full daylight.

Optically Transparent Wood from a Nanoporous Cellulosic Template: Combining Functional and Structural Performance.

PubMed

Li, Yuanyuan; Fu, Qiliang; Yu, Shun; Yan, Min; Berglund, Lars

2016-04-11

Optically transparent wood (TW) with transmittance as high as 85% and haze of 71% was obtained using a delignified nanoporous wood template. The template was prepared by removing the light-absorbing lignin component, creating nanoporosity in the wood cell wall. Transparent wood was prepared by successful impregnation of lumen and the nanoscale cellulose fiber network in the cell wall with refractive-index-matched prepolymerized methyl methacrylate (MMA). During the process, the hierarchical wood structure was preserved. Optical properties of TW are tunable by changing the cellulose volume fraction. The synergy between wood and PMMA was observed for mechanical properties. Lightweight and strong transparent wood is a potential candidate for lightweight low-cost, light-transmitting buildings and transparent solar cell windows.

DFT calculations of electronic and optical properties of SrS with LDA, GGA and mGGA functionals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Shatendra, E-mail: shatendra@gmai.com; Sharma, Jyotsna; Sharma, Yogita

2016-05-06

The theoretical investigations of electronic and optical properties of SrS are made using the first principle DFT calculations. The calculations are performed for the local-density approximation (LDA), generalized gradient approximation (GGA) and for an alternative form of GGA i.e. metaGGA for both rock salt type (B1, Fm3m) and cesium chloride (B2, Pm3m) structures. The band structure, density of states and optical spectra are calculated under various available functional. The calculations with LDA and GGA functional underestimate the values of band gaps with all functional, however the values with mGGA show reasonably good agreement with experimental and those calculated by usingmore » other methods.« less

Nonlinear optics of astaxanthin thin films

NASA Astrophysics Data System (ADS)

Esser, A.; Fisch, Herbert; Haas, Karl-Heinz; Haedicke, E.; Paust, J.; Schrof, Wolfgang; Ticktin, Anton

1993-02-01

Carotinoids exhibit large nonlinear optical properties due to their extended (pi) -electron system. Compared to other polyenes which show a broad distribution of conjugation lengths, carotinoids exhibit a well defined molecular structure, i.e. a well defined conjugation length. Therefore the carotinoid molecules can serve as model compounds to study the relationship between structure and nonlinear optical properties. In this paper the synthesis of four astaxanthins with C-numbers ranging from 30 to 60, their preparation into thin films, wavelength dispersive Third Harmonic Generation (THG) measurements and some molecular modelling calculations will be presented. Resonant (chi) (3) values reach 1.2(DOT)10-10 esu for C60 astaxanthin. In the nonresonant regime a figure of merit (chi) (3)/(alpha) of several 10-13 esu-cm is demonstrated.

Au-Ag-Cu nano-alloys: tailoring of permittivity

NASA Astrophysics Data System (ADS)

Hashimoto, Yoshikazu; Seniutinas, Gediminas; Balčytis, Armandas; Juodkazis, Saulius; Nishijima, Yoshiaki

2016-04-01

Precious metal alloys enables new possibilities to tailor materials for specific optical functions. Here we present a systematic study of the effects of a nanoscale alloying on the permittivity of Au-Ag-Cu metals at 38 different atomic mixing ratios. The permittivity was measured and analyzed numerically by applying the Drude model. X-ray diffraction (XRD) revealed the face centered cubic lattice of the alloys. Both, optical spectra and XRD results point towards an equivalent composition-dependent electron scattering behavior. Correlation between the fundamental structural parameters of alloys and the resulting optical properties is elucidated. Plasmonic properties of the Au-Ag-Cu alloy nanoparticles were investigated by numerical simulations. Guidelines for designing plasmonic response of nano- structures and their patterns are presented from the material science perspective.

High Throughput Light Absorber Discovery, Part 2: Establishing Structure-Band Gap Energy Relationships.

PubMed

Suram, Santosh K; Newhouse, Paul F; Zhou, Lan; Van Campen, Douglas G; Mehta, Apurva; Gregoire, John M

2016-11-14

Combinatorial materials science strategies have accelerated materials development in a variety of fields, and we extend these strategies to enable structure-property mapping for light absorber materials, particularly in high order composition spaces. High throughput optical spectroscopy and synchrotron X-ray diffraction are combined to identify the optical properties of Bi-V-Fe oxides, leading to the identification of Bi 4 V 1.5 Fe 0.5 O 10.5 as a light absorber with direct band gap near 2.7 eV. The strategic combination of experimental and data analysis techniques includes automated Tauc analysis to estimate band gap energies from the high throughput spectroscopy data, providing an automated platform for identifying new optical materials.

Structural and optical properties of antimony-germanate-borate glass and glass fiber co-doped Eu3+ and Ag nanoparticles.

PubMed

Zmojda, Jacek; Kochanowicz, Marcin; Miluski, Piotr; Baranowska, Agata; Pisarski, Wojciech A; Pisarska, Joanna; Jadach, Renata; Sitarz, Maciej; Dorosz, Dominik

2018-08-05

In the paper analysis of structural and luminescent properties of antimony-germanate-borate glasses and glass fiber co-doped with 0.6AgNO 3 /0.2Eu 2 O 3 are presented. Heat treatment of the fabricated glass and optical fiber (400 °C, 12 h) enabled to obtain Ag nanoparticles (NPs) with average size 30-50 nm on their surface. It has been proofed that silver ions migrate to the glass surface, where they are reduced to Ag 0 nanoparticles. Simultaneously, FTIR analysis showed that heat treatment of the glass and optical fiber increases the local symmetry of the Eu 3+ site. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthesis and characterization of Graphene oxide/Zinc oxide nanorods sandwich structure

NASA Astrophysics Data System (ADS)

Boukhoubza, I.; Khenfouch, M.; Achehboune, M.; Mouthudi, B.; Zorkani, I.; Jorio, A.

2018-03-01

Graphene-ZnO nanostructures composite materials have been used as very efficient candidates for various optoelectronic applications. Nowadays, the composite structure formation of ZnO nanostructures with graphene or graphene oxide is a novel, cost effective and efficient approach to control the morphology, surface defect states, band gap of ZnO nanocrystals. In this paper, we have prepared ZnO nanorods between two layers graphene oxide (GO/ZnO NRs/GO) via a simple hydrothermal method. Their morphology, structural and optical properties have been investigated. The obtained results of our composites GO/ZnO NRs/GO presented here showing an enhancement in the structural and optical properties. Thus may hold great promise to the development of the optoelectronic devices.

Peptide Integrated Optics.

PubMed

Handelman, Amir; Lapshina, Nadezda; Apter, Boris; Rosenman, Gil

2018-02-01

Bio-nanophotonics is a wide field in which advanced optical materials, biomedicine, fundamental optics, and nanotechnology are combined and result in the development of biomedical optical chips. Silk fibers or synthetic bioabsorbable polymers are the main light-guiding components. In this work, an advanced concept of integrated bio-optics is proposed, which is based on bioinspired peptide optical materials exhibiting wide optical transparency, nonlinear and electrooptical properties, and effective passive and active waveguiding. Developed new technology combining bottom-up controlled deposition of peptide planar wafers of a large area and top-down focus ion beam lithography provides direct fabrication of peptide optical integrated circuits. Finding a deep modification of peptide optical properties by reconformation of biological secondary structure from native phase to β-sheet architecture is followed by the appearance of visible fluorescence and unexpected transition from a native passive optical waveguiding to an active one. Original biocompatibility, switchable regimes of waveguiding, and multifunctional nonlinear optical properties make these new peptide planar optical materials attractive for application in emerging technology of lab-on-biochips, combining biomedical photonic and electronic circuits toward medical diagnosis, light-activated therapy, and health monitoring. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

VLBA Observations of Low Luminosity Flat Spectrum Radio Galaxies and BL Lac Objects: Polarisation Properties

NASA Astrophysics Data System (ADS)

Bondi, M.; Dallacasa, D.; Stanghellini, C.; Marchã, M. J. M.

We obtained two-epoch VLBA observations at 5 GHz of a list of radio galaxies drawn from the 200 mJy sample (Marcha et al. 1996). The objects selected for milli-arcsecond scale observations are classified, on the basis of their optical spectroscopic and polarimetric properties, as BL Lac objects, normal weak line radio galaxies, broad line radio galaxies, and transition objects (those with intermediate properties). We present preliminary results on the radio polarization properties, on the milli-arcsecond scale, of objects with different optical properties and discuss structural variations detected from the two epochs.

Thermal effects on an embedded grating sensor in an FRP structure

NASA Astrophysics Data System (ADS)

Lau, Kin-tak; Yuan, Libo; Zhou, Li-min

2001-08-01

Much research has been carried out in the field of using optical fibre sensors as internal strain and temperature measuring devices for advanced composite structures in recent years. The specific application is the use of embedded optical fibre sensors for smart composite reinforcement for strain monitoring in an innovative civil engineering structure, particularly for the structure after rehabilitation. Researchers have also paid attention to using the optical fibre sensor for monitoring the condition of composite materials during manufacturing and curing processes. However, heat induced in the curing process may influence the accuracy of measurement and eventuate in causing damage at the bond interface between the optical fibre and the surrounding matrix material because of the different thermal properties of silica fibre and composite materials. In this paper, a simple theoretical model is introduced to determine the interfacial properties of the embedded optical fibre system in composite laminates with different values of the coefficient of thermal expansion under different temperature environments. A finite-element method is used to compare the result from the theoretical prediction. The results show that the maximum shear stress in the coating layer decreases with increasing surrounding temperature when the optical fibre is embedded into carbon and Kevlar fibre composites. In contrast, increasing the temperature when the optical fibre is embedded into glass fibre composite results in the increase of maximum shear stress of the material. The compaction pressure distribution along the circumference of the coating layer also varies with temperature.

Structural and Luminescence Properties of Lu2O3:Eu3+ F127 Tri-Block Copolymer Modified Thin Films Prepared by Sol-Gel Method

PubMed Central

de Jesus Morales Ramírez, Angel; Hernández, Margarita García; Murillo, Antonieta García; de Jesús Carrillo Romo, Felipe; Palmerin, Joel Moreno; Velazquez, Dulce Yolotzin Medina; Jota, María Luz Carrera

2013-01-01

Lu2O3:Eu3+ transparent, high density, and optical quality thin films were prepared using the sol-gel dip-coating technique, starting with lutetium and europium nitrates as precursors and followed by hydrolysis in an ethanol-ethylene glycol solution. Acetic acid and acetylacetonate were incorporated in order to adjust pH and as a sol stabilizer. In order to increment the thickness of the films and orient the structure, F127 Pluronic acid was incorporated during the sol formation. Structural, morphological, and optical properties of the films were investigated for different F127/Lu molar ratios (0–5) in order to obtain high optical quality films with enhanced thickness compared with the traditional method. X-ray diffraction (XRD) shows that the films present a highly oriented cubic structure <111> beyond 1073 K for a 3-layer film, on silica glass substrates. The thickness, density, porosity, and refractive index evolution of the films were investigated by means of m-lines microscopy along with the morphology by scanning electron microscope (SEM) and luminescent properties. PMID:28809336

Effects of dopant induced defects on structural, multiferroic and optical properties of Bi1-x Pb x FeO3 (0 ≤ x ≤ 0.3) ceramics

NASA Astrophysics Data System (ADS)

Hassnain Jaffari, G.; Aftab, M.; Samad, Abdus; Mumtaz, Fiza; Awan, M. S.; Shah, S. Ismat

2018-01-01

Bi1-x Pb x FeO3 (0 ≤ x ≤ 0.3) has been characterized in detail with an aim to identify role of defect such as dopant, various vacancies, grain boundaries etc, and their effect on structural, optical and multiferroic properties. Structural analysis revealed that Pb substitution transforms the rhombohedral phase of BiFeO3 to the pseudocubic phase for x ≥ 0.15, consistently all vibrational Raman modes associated with the rhombohedral phase are found disappeared. Optical response revealed weakening of the d-d transitions with Pb addition indicating change in the Fe atoms environment consistent with the transition from non-centrosymmetric to the centrosymmetric structure. Transport and dielectric responses are explained in terms of hopping due to the presence of defects like oxygen vacancies and grain boundary conduction. In the high temperature regime, grain boundary conduction led to decrease in resistivity with the presence of a hump that is associated with hopping conduction. Extrinsic contributions in the transport properties correlate well with dielectric response. Magnetic and ferroelectric responses are also presented where role of oxygen vacancies defects has been clearly identified.

Reversible Structural Swell-Shrink and Recoverable Optical Properties in Hybrid Inorganic-Organic Perovskite.

PubMed

Zhang, Yupeng; Wang, Yusheng; Xu, Zai-Quan; Liu, Jingying; Song, Jingchao; Xue, Yunzhou; Wang, Ziyu; Zheng, Jialu; Jiang, Liangcong; Zheng, Changxi; Huang, Fuzhi; Sun, Baoquan; Cheng, Yi-Bing; Bao, Qiaoliang

2016-07-26

Ion migration in hybrid organic-inorganic perovskites has been suggested to be an important factor for many unusual behaviors in perovskite-based optoelectronics, such as current-voltage hysteresis, low-frequency giant dielectric response, and the switchable photovoltaic effect. However, the role played by ion migration in the photoelectric conversion process of perovskites is still unclear. In this work, we provide microscale insights into the influence of ion migration on the microstructure, stability, and light-matter interaction in perovskite micro/nanowires by using spatially resolved optical characterization techniques. We observed that ion migration, especially the migration of MA(+) ions, will induce a reversible structural swell-shrink in perovskites and recoverably affect the reflective index, quantum efficiency, light-harvesting, and photoelectric properties. The maximum ion migration quantity in perovskites was as high as approximately 30%, resulting in lattice swell or shrink of approximately 4.4%. Meanwhile, the evidence shows that ion migration in perovskites could gradually accelerate the aging of perovskites because of lattice distortion in the reversible structural swell-shrink process. Knowledge regarding reversible structural swell-shrink and recoverable optical properties may shed light on the development of optoelectronic and converse piezoelectric devices based on perovskites.

Investigation of Zinc Oxide-Loaded Poly(Vinyl Alcohol) Nanocomposite Films in Tailoring Their Structural, Optical and Mechanical Properties

NASA Astrophysics Data System (ADS)

Aslam, Muhammad; Kalyar, Mazhar Ali; Raza, Zulfiqar Ali

2018-04-01

Wurtzite ZnO nanoparticles, as a nanofiller, were incorporated in a poly(vinyl alcohol) (PVA) matrix to prepare multipurpose nanocomposite films using a solution casting approach. Some advanced analytical techniques were used to investigate the properties of prepared nanocomposite films. The mediation of ZnO nanofillers resulted in modification of structural, optical and mechanical properties of nanocomposite films. A comprehensive band structure investigation might be useful for designing technological applications like in optoelectronic devices. The experimental results were found to be closely dependent on the nanofiller contents. Some theoretical models like Tauc's and Wemple-DiDomenico, were employed to investigate the band structure parameters. The imaginary part of the dielectric constant was used to investigate the band gap. Then, the Helpin-Tsai model was employed to predict Young's moduli of the prepared nanocomposite films. On 3 wt.% ZnO nanofiller loading, the optical band gap of the PVA-based nanocomposite film was decreased from 5.26 eV to 3 eV, the tensile strength increased from 25.3 MPa to 48 MPa and Young's modulus increased from 144 MPa to 544 MPa.

Investigation of Zinc Oxide-Loaded Poly(Vinyl Alcohol) Nanocomposite Films in Tailoring Their Structural, Optical and Mechanical Properties

NASA Astrophysics Data System (ADS)

Aslam, Muhammad; Kalyar, Mazhar Ali; Raza, Zulfiqar Ali

2018-07-01

Wurtzite ZnO nanoparticles, as a nanofiller, were incorporated in a poly(vinyl alcohol) (PVA) matrix to prepare multipurpose nanocomposite films using a solution casting approach. Some advanced analytical techniques were used to investigate the properties of prepared nanocomposite films. The mediation of ZnO nanofillers resulted in modification of structural, optical and mechanical properties of nanocomposite films. A comprehensive band structure investigation might be useful for designing technological applications like in optoelectronic devices. The experimental results were found to be closely dependent on the nanofiller contents. Some theoretical models like Tauc's and Wemple-DiDomenico, were employed to investigate the band structure parameters. The imaginary part of the dielectric constant was used to investigate the band gap. Then, the Helpin-Tsai model was employed to predict Young's moduli of the prepared nanocomposite films. On 3 wt.% ZnO nanofiller loading, the optical band gap of the PVA-based nanocomposite film was decreased from 5.26 eV to 3 eV, the tensile strength increased from 25.3 MPa to 48 MPa and Young's modulus increased from 144 MPa to 544 MPa.

First principles study of structural, electronic and optical properties of polymorphic forms of Rb 2Te

NASA Astrophysics Data System (ADS)

Alay-e-Abbas, S. M.; Shaukat, A.

2011-05-01

First-principles density functional theory calculations have been performed for structural, electronic and optical properties of three polymorphic forms of rubidium telluride. Our calculations show that the sequence of pressure induced phase transitions for Rb 2Te is Fm3¯m → Pnma → P6 3/mmc which is governed by the coordination numbers of the anions. From our calculated low transition pressure value for the Fm3¯m phase to the Pnma phase transition of Rb 2Te, the experimentally observed meta-stability of Fm3¯m phase at ambient conditions seems reasonable. The electronic band structure has been calculated for all the three phases and the change in the energy band gap is discussed for the transitioning phases. The energy band gaps obtained for the three phases of Rb 2Te decrease on going from the meta-stable phase to the high-pressure phases. Total and partial density of states for the polymorphs of Rb 2Te has been computed to elucidate the contribution of various atomic states on the electronic band structure. Furthermore, optical properties for all the polymorphic forms have been presented in form of the complex dielectric function.

Tuning the optical response of a dimer nanoantenna using plasmonic nanoring loads

PubMed Central

Panaretos, Anastasios H.; Yuwen, Yu A.; Werner, Douglas H.; Mayer, Theresa S.

2015-01-01

The optical properties of a dimer type nanoantenna loaded with a plasmonic nanoring are investigated through numerical simulations and measurements of fabricated prototypes. It is demonstrated that by judiciously choosing the nanoring geometry it is possible to engineer its electromagnetic properties and thus devise an effective wavelength dependent nanoswitch. The latter provides a mechanism for controlling the coupling between the dimer particles, and in particular to establish a pair of coupled/de-coupled states for the total structure, that effectively results in its dual mode response. Using electron beam lithography the targeted structure has been accurately fabricated and the desired dual mode response of the nanoantenna was experimentally verified. The response of the fabricated structure is further analyzed numerically. This permits the visualization of the electromagnetic fields and polarization surface charge distributions when the structure is at resonance. In this way the switching properties of the plasmonic nanoring are revealed. The documented analysis illustrates the inherent tuning capabilities that plasmonic nanorings offer, and furthermore paves the way towards a practical implementation of tunable optical nanoantennas. Additionally, our analysis through an effective medium approach introduces the nanoring as a compact and efficient solution for realizing nanoscale circuits. PMID:25961804

Effect of Phosphine-Free Selenium Precursor Reactivity on The Optical and Vibrational properties of Colloidal CdSe Nanocrystals

NASA Astrophysics Data System (ADS)

Thi, L. A.; Lieu, N. T. T.; Hoa, N. M.; Tran, N.; Binh, N. T.; Quang, V. X.; Nghia, N. X.

2018-03-01

Phosphine-free selenium precursor solutions have been prepared by heating at temperatures ranging from 160 °C to 240 °C and studied by means of infrared absorption spectroscopy. The colloidal CdSe nanocrystals (NCs) synthesized from all those solutions by the wet chemical method. The influence of heating temperature on the chemical reactivity of selenium precursor and its role on the optical and vibrational properties of CdSe NCs are discussed in details. Their morphology, particle size, structural, optical and vibrational properties were investigated using transmission electron microscopy, X-ray diffraction, UV-Vis, fluorescence and Raman spectroscopy, respectively.

Magneto-optical properties of cerium substituted yttrium iron garnet films with reduced thermal budget for monolithic photonic integrated circuits.

PubMed

Goto, Taichi; Onbaşlı, Mehmet C; Ross, C A

2012-12-17

Thin films of polycrystalline cerium substituted yttrium iron garnet (CeYIG) were grown on an yttrium iron garnet (YIG) seed layer on Si and Si-on-insulator substrates by pulsed laser deposition, and their optical and magneto-optical properties in the near-IR region were measured. A YIG seed layer of ~30 nm thick processed by rapid thermal anneal at 800°C provided a virtual substrate to promote crystallization of the CeYIG. The effect of the thermal budget of the YIG/CeYIG growth process on the film structure, magnetic and magnetooptical properties was determined.

Optical properties of B12P2 crystals: Ab initio calculation and EELS

NASA Astrophysics Data System (ADS)

Reshetniak, V. V.; Mavrin, B. N.; Medvedev, V. V.; Perezhogin, I. A.; Kulnitskiy, B. A.

2018-05-01

We report an experimental and theoretical investigation of the electronic structure and optical properties of B12P2 crystals in the energy range up to 60 eV. Experimental studies are performed by the method of electron energy loss spectroscopy, and theoretical studies are carried out using density functional theory and the GW approximation. The calculated dependence of the energy loss function is in agreement with the experiment. Based on the results of the calculations, we determine the optical properties of B12P2 crystals and investigate their anisotropy. The dispersion and density of electronic states are calculated and analyzed.

First-principles study on silicon atom doped monolayer graphene

NASA Astrophysics Data System (ADS)

Rafique, Muhammad; Shuai, Yong; Hussain, Nayyar

2018-01-01

This paper illustrates the structural, electronic and optical properties of individual silicon (Si) atom-doped single layer graphene using density functional theory method. Si atom forms tight bonding with graphene layer. The effect of doping has been investigated by varying the concentration of Si atoms from 3.125% to 9.37% (i.e. From one to three Si atoms in 4 × 4 pure graphene supercell containing 32 carbon atoms), respectively. Electronic structure, partial density of states (PDOS) and optical properties of pure and Si atom-doped graphene sheet were calculated using VASP (Vienna ab-initio Simulation Package). The calculated results for pure graphene sheet were then compared with Si atom doped graphene. It is revealed that upon Si doping in graphene, a finite band gap appears at the high symmetric K-point, thereby making graphene a direct band gap semiconductor. Moreover, the band gap value is directly proportional to the concentration of impurity Si atoms present in graphene lattice. Upon analyzing the optical properties of Si atom-doped graphene structures, it is found that, there is significant change in the refractive index of the graphene after Si atom substitution in graphene. In addition, the overall absorption spectrum of graphene is decreased after Si atom doping. Although a significant red shift in absorption is found to occur towards visible range of radiation when Si atom is substituted in its lattice. The reflectivity of graphene improves in low energy region after Si atom substitution in graphene. These results can be useful for tuning the electronic structure and to manipulate the optical properties of graphene layer in the visible region.

Unanticipated C=C bonds in covalent monolayers on silicon revealed by NEXAFS.

PubMed

Lee, Michael V; Lee, Jonathan R I; Brehmer, Daniel E; Linford, Matthew R; Willey, Trevor M

2010-02-02

Interfaces are crucial to material properties. In the case of covalent organic monolayers on silicon, molecular structure at the interface controls the self-assembly of the monolayers, which in turn influences the optical properties and electrical transport. These properties intrinsically affect their application in biology, tribology, optics, and electronics. We use near-edge X-ray absorption fine structure spectroscopy to show that the most basic covalent monolayers formed from 1-alkenes on silicon retain a double bond in one-fifth to two-fifths of the resultant molecules. Unsaturation in the predominantly saturated monolayers will perturb the regular order and affect the dependent properties. The presence of unsaturation in monolayers produced by two different methods also prompts the re-evaluation of other radical-based mechanisms for forming covalent monolayers on silicon.

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

NASA Astrophysics Data System (ADS)

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, and field-induced circular dichroism of the emitted light. These characteristics are indeed inherent to the NW crystal symmetry. Such an exhaustive summary of the electronic properties of WZ InP NWs (energy, symmetry, thermal-, and pressure-induced shift of near band gap electronic bands, impurities binding energy, WZ and ZB band-offset values, exciton lifetime, exciton, electron, and hole effective masses) is valuable in the prediction of fundamental device parameters or as a reference for detailed band-structure calculations, as summarized in the last section (Sec. V), where also the open issues are critically discussed.

Customization of Protein Single Nanowires for Optical Biosensing.

PubMed

Sun, Yun-Lu; Sun, Si-Ming; Wang, Pan; Dong, Wen-Fei; Zhang, Lei; Xu, Bin-Bin; Chen, Qi-Dai; Tong, Li-Min; Sun, Hong-Bo

2015-06-24

An all-protein single-nanowire optical biosensor is constructed by a facile and general femtosecond laser direct writing approach with nanoscale structural customization. As-formed protein single nanowires show excellent optical properties (fine waveguiding performance and bio-applicable transmission windows), and are utilized as evanescent optical nanobiosensors for label-free biotin detection. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Light trapping structures in wing scales of butterfly Trogonoptera brookiana.

PubMed

Han, Zhiwu; Niu, Shichao; Shang, Chunhui; Liu, Zhenning; Ren, Luquan

2012-04-28

The fine optical structures in wing scales of Trogonoptera brookiana, a tropical butterfly exhibiting efficient light trapping effect, were carefully examined and the reflectivity was measured using reflectance spectrometry. The optimized 3D configuration of the coupling structure was determined using SEM and TEM data, and the light trapping mechanism of butterfly scales was studied. It is found that the front and back sides of butterfly wings possess different light trapping structures, but both can significantly increase the optical path and thus result in almost total absorption of all incident light. An optical model was created to check the properties of this light trapping structure. The simulated reflectance spectra are in concordance with the experimental ones. The results reliably confirm that these structures induce efficient light trapping effect. This functional "biomimetic structure" would have a potential value in wide engineering and optical applications. This journal is © The Royal Society of Chemistry 2012

Superhydrophilic nanopillar-structured quartz surfaces for the prevention of biofilm formation in optical devices

NASA Astrophysics Data System (ADS)

Han, Soo; Ji, Seungmuk; Abdullah, Abdullah; Kim, Duckil; Lim, Hyuneui; Lee, Donghyun

2018-01-01

Bacterial biofilm formation on optical devices such as contact lenses, optical glasses, endoscopic devices, and microscopic slides and lenses are major concerns in the field of medicine and biomedical engineering. To solve these problems, here we present the first report of superhydrophilic transparent nanopillar-structured surfaces with bactericidal properties. To construct bactericidal surfaces, we imitated a topological mechanism found in nature in which nanopillar-structured surfaces cause a mechanical disruption of the outer cell membranes of bacteria, resulting in bacterial cell death. We used nanosphere lithography to fabricate nanopillars with various sharpnesses and heights on a quartz substrate. Water contact angle and light reflectance measurements revealed superhydrophilic, antifogging and antireflective properties, which are important for use in optical devices. To determine bactericidal efficiency, the fabricated surfaces were incubated and tested against two Gram-negative bacteria associated with biofilm formation and various diseases in humans, Pseudomonas aeruginosa and Escherichia coli. The highest bactericidal activity was achieved with nanopillars that measured 300 nm in height and 10 nm in apex diameter. Quartz substrates patterned with such nanopillars killed ∼38,000 P. aeruginosa and ∼27,000 E. coli cells cm-2 min-1, respectively. Thus, the newly designed nanopillar-structured bactericidal surfaces are suitable for use in the development of superhydrophilic and transparent optical devices.

Tailoring physical properties of transglutaminase-modified gelatin films by varying drying temperature

USDA-ARS?s Scientific Manuscript database

Gelatin films prepared with or without transglutaminase (TGase) and dried at 15, 25 and 35 °C were analyzed for polymeric network structure, chemical composition and physical properties. Differences in protein network structure were observed by optical microscopy analysis in freeze-dried film-formin...

Bioinspired Omnidirectional Self-Stable Reflectors with Multiscale Hierarchical Structures.

PubMed

Han, Zhiwu; Mu, Zhengzhi; Li, Bo; Feng, Xiaoming; Wang, Ze; Zhang, Junqiu; Niu, Shichao; Ren, Luquan

2017-08-30

Structured surfaces, demonstrating various wondrous physicochemical performances, are ubiquitous phenomena in nature. Butterfly wings with impressive structural colors are an interesting example for multiscale hierarchical structures (MHSs). However, most natural structural colors are relatively unstable and highly sensitive to incident angles, which limit their potential practical applications to a certain extent. Here, we reported a bioinspired color reflector with omnidirectional reflective self-stable (ORS) properties, which is inspired by the wing scales of Papilio palinurus butterfly. Through experimental exploration and theoretical analysis, it was found that the vivid colors of such butterfly wings are structure-based and possess novel ORS properties, which attributes to the multiple optical actions between light and the complex structures coupling the inverse opal-like structures (IOSs) and stacked lamellar ridges (SLRs). On the basis of this, we designed and successfully fabricated the SiO 2 -based bioinspired color reflectors (BCRs) through a facile and effective biotemplate method. It was confirmed that the MHSs in biotemplate are inherited by the obtained SiO 2 -based BCRs. More importantly, the SiO 2 -based BCRs also demonstrated the similar ORS properties in a wide wavelength range. We forcefully anticipate that the reported MHS-based ORS performance discovered in butterfly wing scales here could offer new thoughts for scientists to solve unstable reflection issues in particular optical field. The involved biotemplate fabrication method offers a facile and effective strategy for fabricating functional nanomaterials or bioinspired nanodevices with 3D complex nanostructures, such as structured optical devices, displays, and optoelectronic equipment.

Conceptual design of tetraazaporphyrin- and subtetraazaporphyrin-based functional nanocarbon materials: electronic structures, topologies, optical properties, and methane storage capacities.

PubMed

Belosludov, Rodion V; Rhoda, Hannah M; Zhdanov, Ravil K; Belosludov, Vladimir R; Kawazoe, Yoshiyuki; Nemykin, Victor N

2016-05-11

A large variety of conceptual three- and fourfold tetraazaporphyrin- and subtetraazaporphyrin-based functional 3D nanocage and nanobarrel structures have been proposed on the basis of in silico design. The designed structures differ in their sizes, topology, porosity, and conjugation properties. The stability of nanocages of Oh symmetry and nanobarrels of D4h symmetry was revealed on the basis of DFT and MD calculations, whereas their optical properties were assessed using a TDDFT approach and a long-range corrected LC-wPBE exchange-correlation functional. It was shown that the electronic structures and vertical excitation energies of the functional nanocage and nanobarrel structures could be easily tuned via their size, topology, and the presence of bridging sp(3) carbon atoms. TDDFT calculations suggest significantly lower excitation energies in fully conjugated nanocages and nanobarrels compared with systems with bridging sp(3) carbon fragments. Based on DFT and TDDFT calculations, the optical properties of the new materials can rival those of known quantum dots and are superior to those of monomeric phthalocyanines and their analogues. The methane gas adsorption properties of the new nanostructures and nanotubes generated by conversion from nanobarrels were studied using an MD simulation approach. The ability to store large quantities of methane (106-216 cm(3) (STP) cm(-3)) was observed in all cases with several compounds being close to or exceeding the DOE target of 180 cm(3) (STP) cm(-3) for material-based methane storage at a pressure of 3.5 MPa and room temperature.

Electronic structure and magneto-optical Kerr effect spectra of ferromagnetic shape-memory Ni-Mn-Ga alloys: Experiment and density functional theory calculations

NASA Astrophysics Data System (ADS)

Uba, S.; Bonda, A.; Uba, L.; Bekenov, L. V.; Antonov, V. N.; Ernst, A.

2016-08-01

In this joint experimental and ab initio study, we focused on the influence of the chemical composition and martensite phase transition on the electronic, magnetic, optical, and magneto-optical properties of the ferromagnetic shape-memory Ni-Mn-Ga alloys. The polar magneto-optical Kerr effect (MOKE) spectra for the polycrystalline sample of the Ni-Mn-Ga alloy of Ni60Mn13Ga27 composition were measured by means of the polarization modulation method over the photon energy range 0.8 ≤h ν ≤5.8 eV in magnetic field up to 1.5 T. The optical properties (refractive index n and extinction coefficient k ) were measured directly by spectroscopic ellipsometry using the rotating analyzer method. To complement experiments, extensive first-principles calculations were made with two different first-principles approaches combining the advantages of a multiple scattering Green function method and a spin-polarized fully relativistic linear-muffin-tin-orbital method. The electronic, magnetic, and MO properties of Ni-Mn-Ga Heusler alloys were investigated for the cubic austenitic and modulated 7M-like incommensurate martensitic phases in the stoichiometric and off-stoichiometric compositions. The optical and MOKE properties of Ni-Mn-Ga systems are very sensitive to the deviation from the stoichiometry. It was shown that the ab initio calculations reproduce well experimental spectra and allow us to explain the microscopic origin of the Ni2MnGa optical and magneto-optical response in terms of interband transitions. The band-by-band decomposition of the Ni2MnGa MOKE spectra is presented and the interband transitions responsible for the prominent structures in the spectra are identified.

Manganese modified structural and optical properties of zinc soda lime silica glasses.

PubMed

Samsudin, Nur Farhana; Matori, Khamirul Amin; Wahab, Zaidan Abdul; Fen, Yap Wing; Liew, Josephine Ying Chi; Lim, Way Foong; Mohd Zaid, Mohd Hafiz; Omar, Nur Alia Sheh

2016-03-20

A series of MnO-doped zinc soda lime silica glass systems was prepared by a conventional melt and quenching technique. In this study, the x-ray diffraction analysis was applied to confirm the amorphous nature of the glasses. Fourier transform infrared spectroscopy shows the glass network consists of MnO₄, SiO₄, and ZnO₄ units as basic structural units. The glass samples under field emission scanning electron microscopy observation demonstrated irregularity in shape and size with glassy phase-like structure. The optical absorption studies revealed that the optical bandgap (E_opt) values decrease with an increase of MnO content. Through the results of various measurements, the doping of MnO in the glass matrix had effects on the performance of the glasses and significantly improved the properties of the glass sample as a potential host for phosphor material.

Microstructure-related properties of magnesium fluoride films at 193nm by oblique-angle deposition.

PubMed

Guo, Chun; Kong, Mingdong; Lin, Dawei; Liu, Cunding; Li, Bincheng

2013-01-14

Magnesium fluoride (MgF2) films deposited by resistive heating evaporation with oblique-angle deposition have been investigated in details. The optical and micro-structural properties of single-layer MgF2 films were characterized by UV-VIS and FTIR spectrophotometers, scanning electron microscope (SEM), atomic force microscope (AFM), and x-ray diffraction (XRD), respectively. The dependences of the optical and micro-structural parameters of the thin films on the deposition angle were analyzed. It was found that the MgF2 film in a columnar microstructure was negatively inhomogeneous of refractive index and polycrystalline. As the deposition angle increased, the optical loss, extinction coefficient, root-mean-square (rms) roughness, dislocation density and columnar angle of the MgF2 films increased, while the refractive index, packing density and grain size decreased. Furthermore, IR absorption of the MgF2 films depended on the columnar structured growth.

Magnetophotonic crystals based on yttrium-iron-garnet infiltrated opals: Magnetization-induced second-harmonic generation

NASA Astrophysics Data System (ADS)

Murzina, T. V.; Kim, E. M.; Kapra, R. V.; Moshnina, I. V.; Aktsipetrov, O. A.; Kurdyukov, D. A.; Kaplan, S. F.; Golubev, V. G.; Bader, M. A.; Marowsky, G.

2006-01-01

Three-dimensional magnetophotonic crystals (MPCs) based on artificial opals infiltrated by yttrium iron garnet (YIG) are fabricated and their structural, optical, and nonlinear optical properties are studied. The formation of the crystalline YIG inside the opal matrix is checked by x-ray analysis. Two templates are used for the infiltration by YIG: bare opals and those covered by a thin platinum film. Optical second-harmonic generation (SHG) technique is used to study the magnetization-induced nonlinear-optical properties of the composed MPCs. A high nonlinear magneto-optical Kerr effect in the SHG intensity is observed at the edge of the photonic band gap of the MPCs.

Quasi-particle energies and optical excitations of hydrogenated and fluorinated germanene.

PubMed

Shu, Huabing; Li, Yunhai; Wang, Shudong; Wang, Jinlan

2015-02-14

Using density functional theory, the G0W0 method and Bethe-Salpeter equation calculations, we systematically explore the structural, electronic and optical properties of hydrogenated and fluorinated germanene. The hydrogenated/fluorinated germanene tends to form chair and zigzag-line configurations and its electronic and optical properties show close geometry dependence. The chair hydrogenated/fluorinated and zigzag-line fluorinated germanene are direct band-gap semiconductors, while the zigzag-line hydrogenated germanene owns an indirect band-gap. Moreover, the quasi-particle corrections are significant and strong excitonic effects with large exciton binding energies are observed. Moreover, the zigzag-line hydrogenated/fluorinated germanene shows highly anisotropic optical responses, which may be used as a good optical linear polarizer.

Optical absorption in planar graphene superlattice: The role of structural parameters

NASA Astrophysics Data System (ADS)

Azadi, L.; Shojaei, S.

2018-04-01

We theoretically studied the optically driven interband transitions in a planar graphene superlattices (PGSL) formed by patterning graphene sheet on laterally hetrostructured substrate as Sio2/hBN. A tunable optical transitions between minibands is observed based on engineering structural parameters. We derive analytically expression for optical absorption from two-band model. Considerable optical absorption is obtained for different ratios between widths of heterostructured substrate and is explained analytically from the view point of wavefunction engineering and miniband dispersion, in details. The role of different statuses of polarization as circular and linear are considered. Our study paves a way toward the control of optical properties of PGSLs to be implemented in optoelectronics devices.

Structural and optical properties of ZnO nanorods on Mg0.2Zn0.8O seed layers grown by hydrothermal method.

PubMed

Kim, Min Su; Kim, Do Yeob; Kim, Sung-O; Leem, Jae-Young

2013-05-01

ZnO nanorods were grown on the Mg0.2Zn0.8O seed layers with different thickness by hydrothermal method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out to investigate the effects of the Mg0.2Zn0.8O seed layer thickness on the structural and the optical properties of the ZnO nanorods. The residual stress in the Mg0.2Zn0.8O seed layers was depended on the thickness while the texture coefficient of the Mg0.2Zn0.8O seed layers was not affected significantly. The smaller full width at half maximum (FWHM) of the ZnO (002) diffraction and near-band-edge emission (NBE) peak and the larger average grain size were observed from the ZnO nanorods grown on the Mg0.2Zn0.8O seed layers with 5 layers (thickness of 350 nm), which indicate the enhancement the structural and the optical properties of the ZnO nanorods.

Effect of Sn doping on structural, mechanical, optical and electrical properties of ZnO nanoarrays prepared by sol-gel and hydrothermal process

NASA Astrophysics Data System (ADS)

Agarwal, Manish Baboo; Sharma, Akash; Malaidurai, M.; Thangavel, R.

2018-05-01

Undoped and Sn doped Zinc oxide nanorods were prepared by two step process: initially growth of seed layers by sol-gel spin coating technique and then zinc oxide nanorods by hydrothermal process using the precursors zinc nitrate hexahydrate, hexamine and tin chloride. The effects on the electrical, optical, mechanical and structural properties for various Sn concentrations were studied. The crystalline phase determination from X-ray diffraction (XRD) confirms that Sn doped ZnO nanorods have hexagonal wurtzite structure. The variations of stress and strain with different doping concentration of Sn in ZnO nanorods were studied. The doping effect on electrical properties and optical bandgap is estimated by current voltage characteristics and absorbance spectra respectively. The surface morphology was studied with field emission scanning electron microscope (FESEM), which shows that the formation of hexagonal nanorods arrays with increasing Sn concentration. The calculated value of Young's modulus of elasticity (Y) for all the samples remains same. These results can be used in optoelectronic devices.

Structure, Morphology, and Optical Properties of Amorphous and Nanocrystalline Gallium Oxide Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, S. Sampath; Rubio, E. J.; Noor-A-Alam, M.

Ga2O3 thin films were produced by sputter deposition by varying the substrate temperature (Ts) in a wide range (Ts=25-800 oC). The structural characteristics and optical properties of Ga2O3 films were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Rutherford backscattering spectrometry (RBS) and spectrophotometric measurements. The effect of growth temperature is significant on the chemistry, crystal structure and morphology of Ga2O3 films. XRD and SEM analyses indicate that the Ga2O3 films grown at lower temperatures were amorphous while those grown at Ts≥500 oC were nanocrystalline. RBS measurements indicate the well-maintained stoichiometry of Ga2O3 films atmore » Ts=300-700 oC. The spectral transmission of the films increased with increasing temperature. The band gap of the films varied from 4.96 eV to 5.17 eV for a variation in Ts in the range 25-800 oC. A relationship between microstructure and optical property is discussed.« less

Investigation of different physical aspects such as structural, mechanical, optical properties and Debye temperature of Fe2ScM (M=P and As) semiconductors: A DFT-based first principles study

NASA Astrophysics Data System (ADS)

Ali, Md. Lokman; Rahaman, Md. Zahidur

2018-04-01

By using first principles calculation dependent on the density functional theory (DFT), we have investigated the mechanical, structural properties and the Debye temperature of Fe2ScM (M=P and As) compounds under various pressures up to 60 GPa. The optical properties have been investigated under zero pressure. Our calculated optimized structural parameters of both the materials are in good agreement with other theoretical predictions. The calculated elastic constants show that Fe2ScM (M=P and As) compounds are mechanically stable under external pressure below 60 GPa. From the elastic constants, the shear modulus G, the bulk modulus B, Young’s modulus E, anisotropy factor A and Poisson’s ratio ν are calculated by using the Voigt-Reuss-Hill approximation. The Debye temperature and average sound velocities are also investigated from the obtained elastic constants. The detailed analysis of all optical functions reveals that both compounds are good dielectric material.

The optical properties of α-Fe2O3 nanostructures synthesized with different immersion time

NASA Astrophysics Data System (ADS)

Ahmad, W. R. W.; Mamat, M. H.; Zoolfakar, A. S.; Khusaimi, Z.; Yusof, M. M.; Ismail, A. S.; Saidi, S. A.; Rusop, M.

2018-05-01

In this study, nanostructured hematite (α-Fe2O3) thin films have been prepared successfully by sonicated immersion method on fluorine-doped tin oxide (FTO) coated glass substrate. The effect of the immersion time on the structural and optical properties of α-Fe2O3 nanostructure were investigated for a variation of immersion time ranging from 1 to 4 hour. From the characterization results, the surface morphology of the sample prepared in 4 hours immersion process has exhibited highest porosity, and the highest absorbance properties were found in the same sample. These results suggest that the different time duration during immersion process play important roles in optical properties of α-Fe2O3 nanostructures.

Optical and magnetic properties of porous anodic alumina/Ni nanocomposite films

NASA Astrophysics Data System (ADS)

Zhang, Jing-Jing; Li, Zi-Yue; Zhang, Zhi-Jun; Wu, Tian-Shan; Sun, Hui-Yuan

2013-06-01

A simple method to tune the optical properties of porous anodic alumina (PAA) films embedded with Ni is reported. The films display highly saturated colors after being synthesized by an ac electrodeposition method. The optical properties of the samples can be effectively tuned by varying the oxidation time of aluminum. The ultrashort Ni nanowires (100 nm long and 50 nm in diameter) present only fcc phase and show no apparent averaged effective magnetic anisotropy. The coercivity mechanism of the Ni nanowires in our case is consistent with fanning mechanism based on a chain-of-spheres model. PAA/Ni films with structural color and magnetic properties have friability-resistant feature and can be used in many areas, including decoration, display, and multifunctional anti-counterfeiting technology.

Network analysis of mesoscale optical recordings to assess regional, functional connectivity.

PubMed

Lim, Diana H; LeDue, Jeffrey M; Murphy, Timothy H

2015-10-01

With modern optical imaging methods, it is possible to map structural and functional connectivity. Optical imaging studies that aim to describe large-scale neural connectivity often need to handle large and complex datasets. In order to interpret these datasets, new methods for analyzing structural and functional connectivity are being developed. Recently, network analysis, based on graph theory, has been used to describe and quantify brain connectivity in both experimental and clinical studies. We outline how to apply regional, functional network analysis to mesoscale optical imaging using voltage-sensitive-dye imaging and channelrhodopsin-2 stimulation in a mouse model. We include links to sample datasets and an analysis script. The analyses we employ can be applied to other types of fluorescence wide-field imaging, including genetically encoded calcium indicators, to assess network properties. We discuss the benefits and limitations of using network analysis for interpreting optical imaging data and define network properties that may be used to compare across preparations or other manipulations such as animal models of disease.

AB INITIO STUDY OF OPTOELECTRONIC PROPERTIES OF SPINEL ZnAl2O4 BEYOND GGA AND LDA

NASA Astrophysics Data System (ADS)

Yousaf, Masood; Saeed, M. A.; Isa, Ahmad Radzi Mat; Rahnamaye Aliabad, H. A.; Noor, N. A.

2012-12-01

Electronic band structure and optical parameters of ZnAl2O4 are investigated by first-principles technique based on a new potential approximation, known as modified Becke-Johnson (mBJ). This method describes the excited states of insulators and semiconductors more accurately The recent direct band gap result by EV-GGA is underestimated by about 15% compared to our band gap value using mBJ-GGA. The value of the band gap of ZnAl2O4 decreases as follows: Eg(mBJ-GGA/LDA) > Eg(GGA) > Eg(LDA). The band structure base optical parametric quantities (dielectric constant, index of refraction, reflectivity and optical conductivity) are also calculated, and their variations with energy range are discussed. The first critical point (optical absorption's edge) in ZnAl2O4 occurs at about 5.26 eV in case of mBJ. This study about the optoelectronic properties indicates that ZnAl2O4 can be used in optical devices.

Comparative quantitative study of astrocytes and capillary distribution in optic nerve laminar regions.

PubMed

Balaratnasingam, Chandrakumar; Kang, Min H; Yu, Paula; Chan, Geoffrey; Morgan, William H; Cringle, Stephen J; Yu, Dao-Yi

2014-04-01

Retinal ganglion cell (RGC) axonal structure and function in the optic nerve head (ONH) is predominantly supported by astrocytes and capillaries. There is good experimental evidence to demonstrate that RGC axons are perturbed in a non-uniform manner following ONH injury and it is likely that the pattern of RGC axonal modification bears some correlation with the quantitative properties of astrocytes and capillaries within laminar compartments. Although there have been some excellent topographic studies concerning glial and microvascular networks in the ONH our knowledge regarding the quantitative properties of these structures are limited. This report is an in-depth quantitative, structural analysis of astrocytes and capillaries in the pre laminar, lamina cribrosa and post laminar compartments of the ONH. 49 optic nerves from human (n = 10), pig (n = 12), horse (n = 6), rat (n = 11) and rabbit (n = 10) eyes are studied. Immunohistochemical and high-magnification confocal microscopy techniques are used to co-localise astrocytes, capillaries and nuclei in the mid-portion of the optic nerve. Quantitative methodology is used to determine the area occupied by astrocyte processes, microglia processes, nuclei density and the area occupied by capillaries in each laminar compartment. Comparisons are made within and between species. Relationships between ONH histomorphometry and astrocyte-capillary constitution are also explored. This study demonstrates that there are significant differences in the quantitative properties of capillaries and astrocytes between the laminar compartments of the human ONH. Astrocyte processes occupied the greatest area in the lamina cribrosa compartment of the human ONH implicating it as an area of great metabolic demands. Microglia were found to occupy only a small proportion of tissue in the rat, rabbit and pig optic nerve suggesting that the astrocyte is the predominant glia cell type in the optic nerve. This study also demonstrates that there is significant uniformity, with respect to astrocyte and capillary constitution, in the post laminar region of species with an unmyelinated anterior optic nerve. This implicates an important role served by oligodendrocytes and myelin in governing the structural characteristics of the post laminar optic nerve. Finally, this study demonstrates that eyes with similar lamina cribrosa structure do not necessarily share an identical cellular constitution with respect to astrocytes. The quantitative properties of astrocytes in the pre laminar and lamina cribrosa regions of the rat, which has a rudimentary lamina cribrosa with only a few collagenous beams, shared more similarities to the human eye than the pig or horse. The quantitative properties of astrocytes and capillaries in the laminar compartments of the ONH provide a basis for understanding the pathogenic mechanisms that are involved in diseases such as glaucoma and ischemic optic neuropathy. The findings in this study also provide valuable information about the distinct advantages of different animal models for studying human optic nerve diseases. Utilisation of structural data provided in this report together with emerging in vivo technology may potentially permit the early identification of RGC axonal injury by quantifying changes in ONH capillaries and astrocytes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Electronic and optical properties of pristine and oxidized borophene

NASA Astrophysics Data System (ADS)

Lherbier, Aurélien; Botello-Méndez, Andrés Rafael; Charlier, Jean-Christophe

2016-12-01

Borophene, a two-dimensional monolayer of boron atoms, was recently synthesized experimentally and was shown to exhibit polymorphism. In its closed-packed triangular form, borophene is expected to exhibit anisotropic metallic character with relatively high electron velocities. At the same time, very low optical conductivities in the infrared-visible light region were predicted. Based on its promising electronic transport properties and its high transparency, borophene could become a genuine lego piece in the 2D materials assembling game known as the van der Waals heterocrystal approach. However, borophene is naturally degraded in ambient conditions and it is therefore important to assess the mechanisms and the effects of oxidation on borophene monolayers. Optical and electronic properties of pristine and oxidized borophene are here investigated by first-principles approaches. The transparent and conductive properties of borophene are elucidated by analyzing the electronic structure and its interplay with light. Optical response of borophene is found to be strongly affected by oxidation, suggesting that optical measurements can serve as an efficient probe for borophene surface contamination.

Microphysical and Optical Properties of Saharan Dust Measured during the ICE-D Aircraft Campaign

NASA Astrophysics Data System (ADS)

Ryder, Claire; Marenco, Franco; Brooke, Jennifer; Cotton, Richard; Taylor, Jonathan

2017-04-01

During August 2015, the UK FAAM BAe146 research aircraft was stationed in Cape Verde off the coast of West Africa. Measurements of Saharan dust, and ice and liquid water clouds, were taken for the ICE-D (Ice in Clouds Experiment - Dust) project - a multidisciplinary project aimed at further understanding aerosol-cloud interactions. Six flights formed part of a sub-project, AER-D, solely focussing on measurements of Saharan dust within the African dust plume. Dust loadings observed during these flights varied (aerosol optical depths of 0.2 to 1.3), as did the vertical structure of the dust, the size distributions and the optical properties. The BAe146 was fully equipped to measure size distributions covering aerosol accumulation, coarse and giant modes. Initial results of size distribution and optical properties of dust from the AER-D flights will be presented, showing that a substantial coarse mode was present, in agreement with previous airborne measurements. Optical properties of dust relating to the measured size distributions will also be presented.

Synthesis, growth, crystal structure, optical and third order nonlinear optical properties of quinolinium derivative single crystal: PNQI

NASA Astrophysics Data System (ADS)

Karthigha, S.; Krishnamoorthi, C.

2018-03-01

An organic quinolinium derivative nonlinear optical (NLO) crystal, 1-ethyl-2-[2-(4-nitro-phenyl)-vinyl]-quinolinium iodide (PNQI) was synthesized and successfully grown by slow evaporation solution growth technique. Formation of a crystalline compound was confirmed by single crystal X-ray diffraction. The quinolinium compound PNQI crystallizes in the triclinic crystal system with a centrosymmetric space group of P-1 symmetry. The molecular structure of PNQI was confirmed by 1H NMR and 13C NMR spectral studies. The thermal properties of the crystal have been investigated by thermogravimetric (TG) and differential scanning calorimetry (DSC) studies. The optical characteristics obtained from UV-Vis-NIR spectral data were described and the cut-off wavelength observed at 506 nm. The etching study was performed to analyse the growth features of PNQI single crystal. The third order NLO properties such as nonlinear refractive index (n2), nonlinear absorption coefficient (β) and nonlinear susceptibility (χ (3)) of the crystal were investigated using Z-scan technique at 632.8 nm of Hesbnd Ne laser.

First principle study of electronic structures and optical properties of Ce-doped SiO2

NASA Astrophysics Data System (ADS)

Cong, Wei-Yan; Lu, Ying-Bo; Zhang, Peng; Guan, Cheng-Bo

2018-05-01

Electronic structures and optical properties of Silicon dioxide (SiO2) systems with and without cerium(Ce) dopant were calculated using the density functional theory. We find that after the Ce incorporation, a new localized impurity band appears between the valance band maximum (VBM) and the conduction band minimum (CBM) of SiO2 system, which is induced mainly by the Ce-4f orbitals. The localized impurity band constructs a bridge between the valence band and the conduction band, making the electronic transition much easier. The calculated optical properties show that in contrast from the pure SiO2 sample, absorption in the visible-light region is found in Ce-doped SiO2 system, which originates from the transition between the valence band and Ce-4f dominated impurity band, as well as the electronic transition from Ce-4f states to Ce-5d states. All calculated results indicate that Ce doping is an effective strategy to improve the optical performance of SiO2 sample, which is in agreement with the experimental results.

Structural stability, electronic, magnetic and optical properties of zincblende Zn0.5V0.5Te under pressure

NASA Astrophysics Data System (ADS)

Yin, Zhu-Hua; Zhang, Jian-Min

2016-10-01

The structural stability, electronic, magnetic and optical properties of zincblende Zn0.5V0.5Te under pressures 0-5 GPa are investigated by the spin-polarized first-principles calculation. Under pressure, the Zn0.5V0.5Te is always half-metal with the total magnetic moment μtot of 3μB / cell mainly contributed by V2+ ion, but the spin-down channel opens a band gap. The Zn0.5V0.5Te also behaves in a ductile manner and is mechanical stable until 3.78 GPa pressure. The static dielectric function ε1 (0) and refractive index n (0) increase with pressure. The two absorption peaks located in energy regions 0-20 eV and 35-50 eV not only increase but also shift to the higher energy region (blue shift) with pressure. So the electronic and optical properties of Zn0.5V0.5Te could be tuned through external pressure, which is beneficial to the electronic and optical applications.

High performance EUV multilayer structures insensitive to capping layer optical parameters.

PubMed

Pelizzo, Maria Guglielmina; Suman, Michele; Monaco, Gianni; Nicolosi, Piergiorgio; Windt, David L

2008-09-15

We have designed and tested a-periodic multilayer structures containing protective capping layers in order to obtain improved stability with respect to any possible changes of the capping layer optical properties (due to oxidation and contamination, for example)-while simultaneously maximizing the EUV reflection efficiency for specific applications, and in particular for EUV lithography. Such coatings may be particularly useful in EUV lithographic apparatus, because they provide both high integrated photon flux and higher stability to the harsh operating environment, which can affect seriously the performance of the multilayer-coated projector system optics. In this work, an evolutive algorithm has been developed in order to design these a-periodic structures, which have been proven to have also the property of stable performance with respect to random layer thickness errors that might occur during coating deposition. Prototypes have been fabricated, and tested with EUV and X-ray reflectometry, and secondary electron spectroscopy. The experimental results clearly show improved performance of our new a-periodic coatings design compared with standard periodic multilayer structures.

Structural and spectroscopic analysis of ex-situ annealed RF sputtered aluminium doped zinc oxide thin films

NASA Astrophysics Data System (ADS)

Otieno, Francis; Airo, Mildred; Erasmus, Rudolph M.; Billing, David G.; Quandt, Alexander; Wamwangi, Daniel

2017-08-01

Aluminium doped zinc oxide thin films are prepared by Radio Frequency magnetron sputtering in pure argon atmosphere at 100 W. The structural results reveal good film adhesion on a silicon substrate (001). The thin films were then subjected to heat treatment in a furnace under ambient air. The structural, morphological, and optical properties of the thin films as a function of deposition time and annealing temperatures have been investigated using Grazing incidence X-Ray Diffraction (GIXRD), Atomic Force Microscopy, and Scanning Electronic Microscopy. The photoluminescence properties of the annealed films showed significant changes in the optical properties attributed to mid gap defects. Annealing increases the crystallite size and the roughness of the film. The crystallinity of the films also improved as evident from the Raman and XRD studies.

Structural tuning of photoluminescence in nanoporous anodic alumina by hard anodization in oxalic and malonic acids

PubMed Central

2012-01-01

We report on an exhaustive and systematic study about the photoluminescent properties of nanoporous anodic alumina membranes fabricated by the one-step anodization process under hard conditions in oxalic and malonic acids. This optical property is analysed as a function of several parameters (i.e. hard anodization voltage, pore diameter, membrane thickness, annealing temperature and acid electrolyte). This analysis makes it possible to tune the photoluminescent behaviour at will simply by modifying the structural characteristics of these membranes. This structural tuning ability is of special interest in such fields as optoelectronics, in which an accurate design of the basic nanostructures (e.g. microcavities, resonators, filters, supports, etc.) yields the control over their optical properties and, thus, upon the performance of the nanodevices derived from them (biosensors, interferometers, selective filters, etc.) PMID:22515214

pH-Induced Modulation of One- and Two-Photon Absorption Properties in a Naphthalene-Based Molecular Probe.

PubMed

Murugan, N Arul; Kongsted, Jacob; Ågren, Hans

2013-08-13

Presently, there is a great demand for small probe molecules that can be used for two-photon excitation microscopy (TPM)-based monitoring of intracellular and intraorganelle activity and pH. The candidate molecules should ideally possess a large two-photon absorption cross section with optical properties sensitive to pH changes. In the present work, we investigate the potential of a methoxy napthalene (MONAP) derivative for its suitability to serve as a pH sensor using TPM. Using an integrated approach rooted in hybrid quantum mechanics/molecular mechanics, the structures, dynamics, and the one- and two-photon properties of the probe in dimethylformamide solvent are studied. It is found that the protonated form is responsible for the optical property of MONAP at moderately low pH, for which the calculated pH-induced red shift is in good agreement with experiments. A 2-fold increase in the two-photon absorption cross section in the IR region of the spectrum is predicted for the moderately low pH form of the probe, suggesting that this can be a potential probe for pH monitoring of living cells. We also propose some design principles aimed at obtaining control of the absorption spectral range of the probe by structural tuning. Our work indicates that the integrated approach employed is capable of capturing the pH-induced changes in structure and optical properties of organic molecular probes and that such in silico tools can be used to draw structure-property relationships to design novel molecular probes suitable for a specific application.

Effects of Doping Ratio of Cobalt and Iron on the Structure and Optical Properties of Bi3.25La0.75Fe(x)Co(1-x)Ti2O12 (X = 0, 0.25, 0.5, 0.75, 1).

PubMed

Song, Myoung Geun; Han, Jun Young; Bark, Chung Wung

2015-10-01

The wide band gap of complex oxides is one of the major obstacles limiting their use in photovoltaic cells. To identify an effective route for tailoring the band gap of complex oxides, this study examined the effects of cobalt and iron doping on lanthanum-modified Bi4Ti3O2-based oxides synthesized using a solid reaction. The structural and optical properties were analyzed by X-ray diffraction and ultraviolet-visible absorption spectroscopy. As a result, the optimal iron to cobalt doping ratio in bismuth titanate powder resulted in an ~1.8 eV decrease in the optical band gap. This new route to reduce the optical bandgap can be adapted to the synthesis of other complex oxides.

Microstructure of the smart composite structures with embedded fiber optic sensing nerves

NASA Astrophysics Data System (ADS)

Liu, Jingyuan; Luo, Fei; Li, Changchun; Ma, Naibin

1997-11-01

The composite structures with embedded optical fiber sensors construct a smart composite structure system, which may have the characteristics of the in-service self-measurement, self- recognition and self-judgement action. In the present work, we studied the microstructures of carbon/epoxy composite laminates with embedded sensing optical fibers, and the integration of optical fiber with composites was also discussed. The preliminary experiment results show that because of the difference between the sensing optical fibers and the reinforcing fibers in their size, the microstructure of the composites with embedded optical fibers will produce partial local changes in the area of embedded optical fiber, these changes may affect the mechanical properties of composite structures. When the optical fibers are embedded parallel to the reinforcing fibers, due to the composite prepregs are formed under a press action during its curing process, the reinforcing fibers can be arranged equably around the optical fibers. But when the optical fibers are embedded perpendicularly to the reinforcement fibers, the resin rich pocket will appear in the composite laminates surrounding the embedded optical fiber. The gas holes will be easily produced in these zones which may produce a premature failure of the composite structure. The photoelastic experiments are also given in the paper.

Structural evolution and electronic properties of n-type doped hydrogenated amorphous silicon thin films

NASA Astrophysics Data System (ADS)

He, Jian; Li, Wei; Xu, Rui; Qi, Kang-Cheng; Jiang, Ya-Dong

2011-12-01

The relationship between structure and electronic properties of n-type doped hydrogenated amorphous silicon (a-Si:H) thin films was investigated. Samples with different features were prepared by plasma enhanced chemical vapor deposition (PECVD) at various substrate temperatures. Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy were used to evaluate the structural evolution, meanwhile, electronic-spin resonance (ESR) and optical measurement were applied to explore the electronic properties of P-doped a-Si:H thin films. Results reveal that the changes in materials structure affect directly the electronic properties and the doping efficiency of dopant.

First-principles study of electronic, optical and thermoelectric properties in cubic perovskite materials AgMO3 (M = V, Nb, Ta)

NASA Astrophysics Data System (ADS)

Mahmood, Asif; Ramay, Shahid M.; Rafique, Hafiz Muhammad; Al-Zaghayer, Yousef; Khan, Salah Ud-Din

2014-05-01

In this paper, first-principles calculations of structural, electronic, optical and thermoelectric properties of AgMO3 (M = V, Nb and Ta) have been carried out using full potential linearized augmented plane wave plus local orbitals method (FP - LAPW + lo) and BoltzTraP code within the framework of density functional theory (DFT). The calculated structural parameters are found to agree well with the experimental data, while the electronic band structure indicates that AgNbO3 and AgTaO3 are semiconductors with indirect bandgaps of 1.60 eV and 1.64 eV, respectively, between the occupied O 2p and unoccupied d states of Nb and Ta. On the other hand, AgVO3 is found metallic due to the overlapping behavior of states across the Fermi level. Furthermore, optical properties, such as dielectric function, absorption coefficient, optical reflectivity, refractive index and extinction coefficient of AgNbO3 and AgTaO3, are calculated for incident photon energy up to 50 eV. Finally, we calculate thermo power for AgNbO3 and AgTaO3 at fixed doping 1019 cm-3. Electron doped thermo power of AgNbO3 shows significant increase over AgTaO3 with temperature.

First principles study on structural, electronic and optical properties of Ga1-xBxP ternary alloys (x = 0, 0.25, 0.5, 0.75 and 1)

NASA Astrophysics Data System (ADS)

Hoat, D. M.; Rivas Silva, J. F.; Méndez Blas, A.

2018-07-01

The structural, electronic and optical properties of GaP, BP binary compounds and their ternary alloys Ga1-xBxP (x = 0.25, 0.5 and 0.75) have been studied by full-potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory (DFT) as implemented in WIEN2k package. Local density approximation (LDA) and generalized gradient approximation (GGA) as proposed by Perdew-Burke-Ernzerhof (PBE), Wu-Cohen (WC) and PBE for solid (PBESol) were used for treatment of exchange-correlation effect in calculations. Additionally, the Tran-Blaha modified Becke-Johnson (mBJ) potential was also employed for electronic and optical calculations due to that it gives very accurate band gap of solids. As B concentration increases, the lattice constant reduces and the energy band gap firstly decreases for small composition x and then it shows increasing trend until pure BP. Our results show that the indirect-direct band gap transition can be reached from x = 0.33. The linear optical properties, such as reflectivity, absorption coefficient, refractive index and optical conductivity of binary compounds and ternary alloys were derived from their calculated complex dielectric function in wide energy range up to 30 eV, and the alloying effect on these properties was also analyzed in detail.

Controlling of the optical properties of the solutions of the PTCDI-C8 organic semiconductor

NASA Astrophysics Data System (ADS)

Erdoğan, Erman; Gündüz, Bayram

2016-09-01

N,N'-Dioctyl-3,4,9,10 perylenedicarboximide (PTCDI-C8) organic semiconductor have vast applications in solar cells, thermoelectric generators, thin film photovoltaics and many other optoelectronic devices. These applications of the materials are based on their spectral and optical properties. The solutions of the PTCDI-C8 for different molarities were prepared and the spectral and optical mesaurements were analyzed. Effects of the molarities on optical properties were investigated. Vibronic structure has been observed based on the absorption bands of PTCDI-C8 semiconductor with seven peaks at 2.292, 2.451, 2.616, 3.212, 3.851, 4.477 and 4.733 eV. The important spectral parameteres such as molar/mass extinction coefficients, absorption coefficient of the PTCDI-C8 molecule were calculated. Optical properties such as angle of incidence/refraction, optical band gap, real and imaginary parts of dielectric constant, loss factor and electrical susceptibility of the the PTCDI-C8 were obtained. Finally, we discussed these parameters for optoelectronic applications and compared with related parameters in literature.

Structural and optical properties of axial silicon-germanium nanowire heterojunctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, X.; Tsybeskov, L., E-mail: tsybesko@njit.edu; Kamins, T. I.

2015-12-21

Detailed studies of the structural and optical properties of axial silicon-germanium nanowire heterojunctions show that despite the 4.2% lattice mismatch between Si and Ge they can be grown without a significant density of structural defects. The lattice mismatch induced strain is partially relieved due to spontaneous SiGe intermixing at the heterointerface during growth and lateral expansion of the Ge segment of the nanowire. The mismatch in Ge and Si coefficients of thermal expansion and low thermal conductivity of Si/Ge nanowire heterojunctions are proposed to be responsible for the thermally induced stress detected under intense laser radiation in photoluminescence and Ramanmore » scattering measurements.« less

The effect of gamma irradiation on chemical, morphology and optical properties of polystyrene nanosphere at various exposure time

NASA Astrophysics Data System (ADS)

Alhaji Yabagi, Jibrin; Isah Kimpa, Mohammed; Nmayaya Muhammad, Muhammad; Rashid, Saiful Bin; Zaidi, Embong; Arif Agam, Mohd

2018-01-01

Irradiation of polymers causes structural, chemical and the optical properties changes. Polystyrene nanosphere was drop coated to substrates and the gamma irradiation was carried out in a Cesium-137 (Cs-137) source chamber at different time (1-5 hours) with constant dose of 30 kGy. Fourier transformation infrared spectroscopy (FTIR) and Raman spectroscopy were employed to characterize the chemical properties of irradiated polystyrene while Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to study the surface morphological changes of the samples. The optical energy band gaps of the thin films were investigated and studied using transmittance and absorbance measurements. The results obtained revealed that as irradiation time increases the optical properties changes and polystyrene gradually undergoes crystal to carbonaceous from its amorphous state. The average particles diameter and roughness of the samples decreases with increasing irradiation time.

Aggregate nanostructures of organic molecular materials.

PubMed

Liu, Huibiao; Xu, Jialiang; Li, Yongjun; Li, Yuliang

2010-12-21

Conjugated organic molecules are interesting materials because of their structures and their electronic, electrical, magnetic, optical, biological, and chemical properties. However, researchers continue to face great challenges in the construction of well-defined organic compounds that aggregate into larger molecular materials such as nanowires, tubes, rods, particles, walls, films, and other structural arrays. Such nanoscale materials could serve as direct device components. In this Account, we describe our recent progress in the construction of nanostructures formed through the aggregation of organic conjugated molecules and in the investigation of the optical, electrical, and electronic properties that depend on the size or morphology of these nanostructures. We have designed and synthesized functional conjugated organic molecules with structural features that favor assembly into aggregate nanostructures via weak intermolecular interactions. These large-area ordered molecular aggregate nanostructures are based on a variety of simpler structures such as fullerenes, perylenes, anthracenes, porphyrins, polydiacetylenes, and their derivatives. We have developed new methods to construct these larger structures including organic vapor-solid phase reaction, natural growth, association via self-polymerization and self-organization, and a combination of self-assembly and electrochemical growth. These methods are both facile and reliable, allowing us to produce ordered and aligned aggregate nanostructures, such as large-area arrays of nanowires, nanorods, and nanotubes. In addition, we can synthesize nanoscale materials with controlled properties. Large-area ordered aggregate nanostructures exhibit interesting electrical, optical, and optoelectronic properties. We also describe the preparation of large-area aggregate nanostructures of charge transfer (CT) complexes using an organic solid-phase reaction technique. By this process, we can finely control the morphologies and sizes of the organic nanostructures on wires, tubes, and rods. Through field emission studies, we demonstrate that the films made from arrays of CT complexes are a new kind of cathode materials, and we systematically investigate the effects of size and morphology on electrical properties. Low-dimension organic/inorganic hybrid nanostructures can be used to produce new classes of organic/inorganic solid materials with properties that are not observed in either the individual nanosize components or the larger bulk materials. We developed the combined self-assembly and templating technique to construct various nanostructured arrays of organic and inorganic semiconductors. The combination of hybrid aggregate nanostructures displays distinct optical and electrical properties compared with their individual components. Such hybrid structures show promise for applications in electronics, optics, photovoltaic cells, and biology. In this Account, we aim to provide an intuition for understanding the structure-function relationships in organic molecular materials. Such principles could lead to new design concepts for the development of new nonhazardous, high-performance molecular materials on aggregate nanostructures.

Structure and Properties of Amorphous Transparent Conducting Oxides

NASA Astrophysics Data System (ADS)

Medvedeva, Julia

Driven by technological appeal, the research area of amorphous oxide semiconductors has grown tremendously since the first demonstration of the unique properties of amorphous indium oxide more than a decade ago. Today, amorphous oxides, such as a-ITO, a-IZO, a-IGZO, or a-ZITO, exhibit the optical, electrical, thermal, and mechanical properties that are comparable or even superior to those possessed by their crystalline counterparts, pushing the latter out of the market. Large-area uniformity, low-cost low-temperature deposition, high carrier mobility, optical transparency, and mechanical flexibility make these materials appealing for next-generation thin-film electronics. Yet, the structural variations associated with crystalline-to-amorphous transition as well as their role in carrier generation and transport properties of these oxides are far from being understood. Although amorphous oxides lack grain boundaries, factors like (i) size and distribution of nanocrystalline inclusions; (ii) spatial distribution and clustering of incorporated cations in multicomponent oxides; (iii) formation of trap defects; and (iv) piezoelectric effects associated with internal strains, will contribute to electron scattering. In this work, ab-initio molecular dynamics (MD) and accurate density-functional approaches are employed to understand how the properties of amorphous ternary and quaternary oxides depend on quench rates, cation compositions, and oxygen stoichiometries. The MD results, combined with thorough experimental characterization, reveal that interplay between the local and long-range structural preferences of the constituent oxides gives rise to a complex composition-dependent structural behavior in the amorphous oxides. The proposed network models of metal-oxygen polyhedra help explain the observed intriguing electrical and optical properties in In-based oxides and suggest ways to broaden the phase space of amorphous oxide semiconductors with tunable properties. The work is supported by NSF-MRSEC program.

Synthesis, Optical and Photoluminescence Properties of Cu-Doped Zno Nano-Fibers Thin Films: Nonlinear Optics

NASA Astrophysics Data System (ADS)

Ganesh, V.; Salem, G. F.; Yahia, I. S.; Yakuphanoglu, F.

2018-03-01

Different concentrations of copper-doped zinc oxide thin films were coated on a glass substrate by sol-gel/spin-coating technique. The structural properties of pure and Cu-doped ZnO films were characterized by different techniques, i.e., atomic force microscopy (AFM), photoluminescence and UV-Vis-NIR spectroscopy. The AFM study revealed that pure and doped ZnO films are formed as nano-fibers with a granular structure. The photoluminescence spectra of these films showed a strong ultraviolet emission peak centered at 392 nm and a strong blue emission peak cantered at 450 nm. The optical band gap of the pure and copper-doped ZnO thin films calculated from optical transmission spectra (3.29-3.23 eV) were found to be increasing with increasing copper doping concentration. The refractive index dispersion curve of pure and Cu-doped ZnO film obeyed the single-oscillator model. The optical dispersion parameters such as E o , E d , and n_{∞}2 were calculated. Further, the nonlinear refractive index and nonlinear optical susceptibility were also calculated and interpreted.

Optical bandgap modelling from the structural arrangement of carbon nanotubes.

PubMed

Butler, Timothy P; Rashid, Ijaz; Montelongo, Yunuen; Amaratunga, Gehan A J; Butt, Haider

2018-06-14

The optical bandgap properties of vertically-aligned carbon nanotube (VACNT) arrays were probed through their interaction with white light, with the light reflected from the rotating arrays measured with a spectrometer. The precise deterministic control over the structure of vertically-aligned carbon nanotube arrays through electron beam lithography and well-controlled growth conditions brings with it the ability to produce exotic photonic crystals over a relatively large area. The characterisation of the behaviour of these materials in the presence of light is a necessary first step toward application. Relatively large area array structures of high-quality VACNTs were fabricated in square, hexagonal, circular and pseudorandom patterned arrays with length scales on the order of those of visible light for the purpose of investigating how they may be used to manipulate an impinging light beam. In order to investigate the optical properties of these arrays a set of measurement apparatus was designed which allowed the accurate measurement of their optical bandgap characteristics. The patterned samples were rotated under the illuminating white light beam, revealing interesting optical bandgap results caused by the changing patterns and relative positions of the scattering elements (VACNTs).

Effect of structural transformation of C+-ion implanted PMMA into quasi-continuous carbonaceous layer on its optical and electrical properties

NASA Astrophysics Data System (ADS)

Arif, Shafaq; Rafique, M. Shahid; Saleemi, Farhat; Sagheer, Riffat

2018-02-01

The samples of Polymethylmethacrylate (PMMA) have been implanted with 500 keV C+-ions at different ion fluences ranging from 9.3 × 1013 to 8.4 × 1014 ions/cm2. The structural modifications are examined by Fourier Transform Infrared and Raman spectral studies. For the investigation of optical, electrical and surface morphological properties of implanted samples UV-Visible spectrometer, four probe apparatus and optical microscope have been employed. The FTIR spectra confirmed the cleavage of chemicals bonds as a consequence of polymer chain scission, whereas, Raman studies revealed the transformation of PMMA structure into quasi-continuous amorphous carbon with increasing ion fluences. A continuous reduction has been observed in the optical band gap of PMMA from 3.16 to 1.42 eV. Moreover, the refractive index, extinction coefficient and electrical conductivity of implanted PMMA are found to be an increasing function of the ion fluence. The micrographic images revealed the signatures of ion-induced defects like cracking, dehydrogenation, stress and swelling on the surface of PMMA. These implanted samples have a potential to be used in the field of optical communications and thin plastic flexible electronics.

Analysis of buried interfaces in multilayer mirrors using grazing incidence extreme ultraviolet reflectometry near resonance edges.

PubMed

Sertsu, M G; Nardello, M; Giglia, A; Corso, A J; Maurizio, C; Juschkin, L; Nicolosi, P

2015-12-10

Accurate measurements of optical properties of multilayer (ML) mirrors and chemical compositions of interdiffusion layers are particularly challenging to date. In this work, an innovative and nondestructive experimental characterization method for multilayers is discussed. The method is based on extreme ultraviolet (EUV) reflectivity measurements performed on a wide grazing incidence angular range at an energy near the absorption resonance edge of low-Z elements in the ML components. This experimental method combined with the underlying physical phenomenon of abrupt changes of optical constants near EUV resonance edges enables us to characterize optical and structural properties of multilayers with high sensitivity. A major advantage of the method is to perform detailed quantitative analysis of buried interfaces of multilayer structures in a nondestructive and nonimaging setup. Coatings of Si/Mo multilayers on a Si substrate with period d=16.4  nm, number of bilayers N=25, and different capping structures are investigated. Stoichiometric compositions of Si-on-Mo and Mo-on-Si interface diffusion layers are derived. Effects of surface oxidation reactions and carbon contaminations on the optical constants of capping layers and the impact of neighboring atoms' interactions on optical responses of Si and Mo layers are discussed.

Au3+ ion implantation on FTO coated glasses: Effect on structural, electrical, optical and phonon properties

NASA Astrophysics Data System (ADS)

Sahu, Bindu; Dey, Ranajit; Bajpai, P. K.

2017-06-01

Effects of 11.00 MeV Au3+ ions implanted in FTO coated (thickness ≈300 nm) silicate glasses on structural, electrical optical and phonon behavior have been explored. It has been observed that metal clustering near the surface and sub-surface region below glass-FTO interface changes electrical and optical properties significantly. Ion implantation does not affect the crystalline structure of the coated films; however, the unit cell volume decreases with increase in fluence and the tetragonal distortion (c/a ratio) also decreases systematically in the implanted samples. The sheet resistivity of the films increases from 11 × 10-5 ohm-cm (in pristine) to 7.5 × 10-4 ohm-cm for highest ion beam fluence ≈1015 ions/cm2. The optical absorption decreases with increasing fluence whereas, the optical transmittance as well as reflectance increases with increasing fluence. The Raman spectra are observed at ∼530 cm-1 and ∼1103 cm-1 in pristine sample. The broad band at 530 cm-1 shifts towards higher wave number in the irradiated samples. This may be correlated with increased disorder and strain relaxation in the samples as a result of ion beam irradiation.

Nonlinear Optical Properties of Carotenoid and Chlorophyll Harmonophores

NASA Astrophysics Data System (ADS)

Tokarz, Danielle Barbara

Information regarding the structure and function of living tissues and cells is instrumental to the advancement of cell biology and biophysics. Nonlinear optical microscopy can provide such information, but only certain biological structures generate nonlinear optical signals. Therefore, structural specificity can be achieved by introducing labels for nonlinear optical microscopy. Few studies exist in the literature about labels that facilitate harmonic generation, coined "harmonophores". This thesis consists of the first major investigation of harmonophores for third harmonic generation (THG) microscopy. Carotenoids and chlorophylls were investigated as potential harmonophores. Their nonlinear optical properties were studied by the THG ratio technique. In addition, a tunable refractometer was built in order to determine their second hyperpolarizability (gamma). At 830 nm excitation wavelength, carotenoids and chlorophylls were found to have large negative gamma values however, at 1028 nm, the sign of gamma reversed for carotenoids and remained negative for chlorophylls. Consequently, at 1028 nm wavelength, THG signal is canceled with mixtures of carotenoids and chlorophylls. Furthermore, when such molecules are covalently bonded as dyads or interact within photosynthetic pigment-protein complexes, it is found that additive effects with the gamma values still play a role, however, the overall gamma value is also influenced by the intra-pigment and inter-pigment interaction. The nonlinear optical properties of aggregates containing chlorophylls and carotenoids were the target of subsequent investigations. Carotenoid aggregates were imaged with polarization-dependent second harmonic generation and THG microscopy. Both techniques revealed crystallographic information pertaining to H and J aggregates and beta-carotene crystalline aggregates found in orange carrot. In order to demonstrate THG enhancement due to labeling, cultured cells were labeled with carotenoid incorporated liposomes. In addition, Drosophila melanogaster larvae muscle as well as keratin structures in the hair cortex were labeled with beta-carotene. Polarization-dependent THG studies may be particularly useful in understanding the structural organization that occurs within biological structures containing carotenoids and chlorophylls such as photosynthetic pigment-protein complexes and carotenoid aggregates in plants and alga. Further, artificial labeling with carotenoids and chlorophylls may be useful in clinical applications since they are nontoxic, nutritionally valuable, and they can aid in visualizing structural changes in cellular components.

Structural and optical properties of Sb65Se35-xGex thin films

NASA Astrophysics Data System (ADS)

Saleh, S. A.; Al-Hajry, A.; Ali, H. M.

2011-07-01

Sb65Se35-xGex (x=0-20 at.%) thin films, prepared by the electron beam evaporation technique on ultrasonically cleaned glass substrates at 300 K, were investigated. The amorphous structure of the thin films was confirmed by x-ray diffraction analysis. The structure was deduced from the Raman spectra measured for all germanium contents in the Sb-Se-Ge matrix. The absorption coefficient (α) of the films was determined by optical transmission measurements. The compositional dependence of the optical band gap is discussed in light of topological and chemical ordered network models.

Optical properties study of nano-composite filled D shape photonic crystal fibre

NASA Astrophysics Data System (ADS)

Udaiyakumar, R.; Mohamed Junaid, K. A.; Janani, T.; Maheswar, R.; Yupapin, P.; Amiri, I. S.

2018-06-01

With the nano-composite materials gaining momentum in the optical field, a new nano-composite filled D shape Photonic Crystal Fiber (PCF) is designed and the various optical properties are investigated with help of Finite Element Method. In the proposed structure the D-shape PCF is made up of silica with embedded silver nanoparticles and air holes are distributed along the fibre. The designed fibre shows various optical properties such as dispersion, birefringence, beat length and loss with respect to wavelength and compared with different filling factor like 0.1, 0.3 and 0.5. From our estimation and comparative analysis, it has been proved that the fibre loss has been decreased with increasing filling factor. Further this also showed flat dispersion at maximum filling factor.

Studies on the growth aspects, structural, thermal, dielectric and third order nonlinear optical properties of solution grown 4-methylpyridinium p-nitrophenolate single crystal

NASA Astrophysics Data System (ADS)

Devi, S. Reena; Kalaiyarasi, S.; Zahid, I. MD.; Kumar, R. Mohan

2016-11-01

An ionic organic optical crystal of 4-methylpyridinium p-nitrophenolate was grown from methanol by slow evaporation method at ambient temperature. Powder and single crystal X-ray diffraction studies revealed the crystal system and its crystalline perfection. The rocking curve recorded from HRXRD study confirmed the crystal quality. FTIR spectral analysis confirmed the functional groups present in the title compound. UV-visible spectral study revealed the optical window and band gap of grown crystal. The thermal, electrical and surface laser damage threshold properties of harvested crystal were examined by using TGA/DTA, LCR/Impedance Analyzer and Nd:YAG laser system respectively. The third order nonlinear optical property of grown crystal was elucidated by Z-scan technique.

Zno Micro/Nanostructures Grown on Sapphire Substrates Using Low-Temperature Vapor-Trapped Thermal Chemical Vapor Deposition: Structural and Optical Properties.

PubMed

Hu, Po-Sheng; Wu, Cheng-En; Chen, Guan-Lin

2017-12-21

In this research, the Zn(C₅H₇O₂)₂·xH₂O-based growth of ZnO micro/nanostructures in a low temperature, vapor-trapped chemical vapor deposition system was attempted to optimize structural and optical properties for potential biomedical applications. By trapping in-flow gas molecules and Zinc vapor inside a chamber tube by partially obstructing a chamber outlet, a high pressure condition can be achieved, and this experimental setup has the advantages of ease of synthesis, being a low temperature process, and cost effectiveness. Empirically, the growth process proceeded under a chamber condition of an atmospheric pressure of 730 torr, a controlled volume flow rate of input gas, N₂/O₂, of 500/500 Standard Cubic Centimeters per Minute (SCCM), and a designated oven temperature of 500 °C. Specifically, the dependence of structural and optical properties of the structures on growth duration and spatially dependent temperature were investigated utilizing scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), and ultraviolet-visible transmission spectroscopy. The experimental results indicate that the grown thin film observed with hexagonal structures and higher structural uniformity enables more prominent structural and optical signatures. XRD spectra present the dominant peaks along crystal planes of (002) and (101) as the main direction of crystallization. In addition, while the structures excited with laser wavelength of 325 nm emit a signature radiation around 380 nm, an ultraviolet lamp with a wavelength of 254 nm revealed distinctive photoluminescence peaks at 363.96 nm and 403.52 nm, elucidating different degrees of structural correlation as functions of growth duration and the spatial gradient of temperature. Transmittance spectra of the structures illustrate typical variation in the wavelength range of 200 nm to 400 nm, and its structural correlation is less significant when compared with PL.

Zno Micro/Nanostructures Grown on Sapphire Substrates Using Low-Temperature Vapor-Trapped Thermal Chemical Vapor Deposition: Structural and Optical Properties

PubMed Central

Hu, Po-Sheng; Wu, Cheng-En; Chen, Guan-Lin

2017-01-01

In this research, the Zn(C5H7O2)2·xH2O-based growth of ZnO micro/nanostructures in a low temperature, vapor-trapped chemical vapor deposition system was attempted to optimize structural and optical properties for potential biomedical applications. By trapping in-flow gas molecules and Zinc vapor inside a chamber tube by partially obstructing a chamber outlet, a high pressure condition can be achieved, and this experimental setup has the advantages of ease of synthesis, being a low temperature process, and cost effectiveness. Empirically, the growth process proceeded under a chamber condition of an atmospheric pressure of 730 torr, a controlled volume flow rate of input gas, N2/O2, of 500/500 Standard Cubic Centimeters per Minute (SCCM), and a designated oven temperature of 500 °C. Specifically, the dependence of structural and optical properties of the structures on growth duration and spatially dependent temperature were investigated utilizing scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), and ultraviolet-visible transmission spectroscopy. The experimental results indicate that the grown thin film observed with hexagonal structures and higher structural uniformity enables more prominent structural and optical signatures. XRD spectra present the dominant peaks along crystal planes of (002) and (101) as the main direction of crystallization. In addition, while the structures excited with laser wavelength of 325 nm emit a signature radiation around 380 nm, an ultraviolet lamp with a wavelength of 254 nm revealed distinctive photoluminescence peaks at 363.96 nm and 403.52 nm, elucidating different degrees of structural correlation as functions of growth duration and the spatial gradient of temperature. Transmittance spectra of the structures illustrate typical variation in the wavelength range of 200 nm to 400 nm, and its structural correlation is less significant when compared with PL. PMID:29267196

Direct correlations of structural and optical properties of three-dimensional GaN/InGaN core/shell micro-light emitting diodes

NASA Astrophysics Data System (ADS)

Sadat Mohajerani, Matin; Müller, Marcus; Hartmann, Jana; Zhou, Hao; Wehmann, Hergo-H.; Veit, Peter; Bertram, Frank; Christen, Jürgen; Waag, Andreas

2016-05-01

Three-dimensional (3D) InGaN/GaN quantum-well (QW) core-shell light emitting diodes (LEDs) are a promising candidate for the future solid state lighting. In this contribution, we study direct correlations of structural and optical properties of the core-shell LEDs using highly spatially-resolved cathodoluminescence spectroscopy (CL) in combination with scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). Temperature-dependent resonant photoluminescence (PL) spectroscopy has been performed to understand recombination mechanisms and to estimate the internal quantum efficiency (IQE).

Photonic crystals, amorphous materials, and quasicrystals

PubMed Central

Edagawa, Keiichi

2014-01-01

Photonic crystals consist of artificial periodic structures of dielectrics, which have attracted much attention because of their wide range of potential applications in the field of optics. We may also fabricate artificial amorphous or quasicrystalline structures of dielectrics, i.e. photonic amorphous materials or photonic quasicrystals. So far, both theoretical and experimental studies have been conducted to reveal the characteristic features of their optical properties, as compared with those of conventional photonic crystals. In this article, we review these studies and discuss various aspects of photonic amorphous materials and photonic quasicrystals, including photonic band gap formation, light propagation properties, and characteristic photonic states. PMID:27877676

Photonic crystals, amorphous materials, and quasicrystals.

PubMed

Edagawa, Keiichi

2014-06-01

Photonic crystals consist of artificial periodic structures of dielectrics, which have attracted much attention because of their wide range of potential applications in the field of optics. We may also fabricate artificial amorphous or quasicrystalline structures of dielectrics, i.e. photonic amorphous materials or photonic quasicrystals. So far, both theoretical and experimental studies have been conducted to reveal the characteristic features of their optical properties, as compared with those of conventional photonic crystals. In this article, we review these studies and discuss various aspects of photonic amorphous materials and photonic quasicrystals, including photonic band gap formation, light propagation properties, and characteristic photonic states.

Bio-inspired fabrication of stimuli-responsive photonic crystals with hierarchical structures and their applications

NASA Astrophysics Data System (ADS)

Lu, Tao; Peng, Wenhong; Zhu, Shenmin; Zhang, Di

2016-03-01

When the constitutive materials of photonic crystals (PCs) are stimuli-responsive, the resultant PCs exhibit optical properties that can be tuned by the stimuli. This can be exploited for promising applications in colour displays, biological and chemical sensors, inks and paints, and many optically active components. However, the preparation of the required photonic structures is the first issue to be solved. In the past two decades, approaches such as microfabrication and self-assembly have been developed to incorporate stimuli-responsive materials into existing periodic structures for the fabrication of PCs, either as the initial building blocks or as the surrounding matrix. Generally, the materials that respond to thermal, pH, chemical, optical, electrical, or magnetic stimuli are either soft or aggregate, which is why the manufacture of three-dimensional hierarchical photonic structures with responsive properties is a great challenge. Recently, inspired by biological PCs in nature which exhibit both flexible and responsive properties, researchers have developed various methods to synthesize metals and metal oxides with hierarchical structures by using a biological PC as the template. This review will focus on the recent developments in this field. In particular, PCs with biological hierarchical structures that can be tuned by external stimuli have recently been successfully fabricated. These findings offer innovative insights into the design of responsive PCs and should be of great importance for future applications of these materials.

Electrooptical properties and structural features of amorphous ITO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amosova, L. P., E-mail: l-amosova@mail.ru

2015-03-15

Thin indium-tin oxide (ITO) films are deposited onto cold substrates by magnetron-assisted sputtering. The dependences of the structural, electrical, and optical properties of the films on the oxygen content in the atmosphere of sputtering and the growth rate are studied. It is shown that, if the substrate temperature is no higher than the ITO crystallization temperature and the conditions of growth deviate from the optimal relationship between the oxygen pressure and the growth rate, the resistance of the layers can be six or seven orders of magnitude higher than the resistance of conducting amorphous layers and reach hundreds of megaohms.more » At the same time, the optical properties of insulating layers in the visible spectral region are completely identical to the properties of the conducing amorphous modification. A conceptual model of defects responsible for the insulating properties of amorphous ITO is proposed.« less

Structural complexity and wide application of two-dimensional S/O type antimonene

NASA Astrophysics Data System (ADS)

Li, T. T.; He, C.; Zhang, W. X.

2018-05-01

Inspired by stable two-dimensional antimonene phases, two new allotropes (S/O and tricycle) antimonenes have been predicted by first-principles calculations in this paper. S/O type antimonene possesses remarkably thermodynamical and dynamical stability, which are comparable to that of buckled type antimonene. The results indicate that S/O type antimonene is a direct band gap semiconductor with a band gap of 2.314 eV and the electronic properties could be effectively tuned by the in-plane strain. In order to explore the potential application, the mechanical properties and optical properties of S/O type antimonene are also extensively studied. It is found the S/O type antimonene is an anisotropic material by the method of analyzing the linear Poisson's ratios and the phonon band structure. These systematical analyses show that S/O type antimonene is a new 2D material with tunable electronic properties, excellent mechanical and optical properties.

Effect of Fe-ion implantation doping on structural and optical properties of CdS thin films

NASA Astrophysics Data System (ADS)

Chandramohan, S.; Kanjilal, A.; Sarangi, S. N.; Majumder, S.; Sathyamoorthy, R.; Som, T.

2010-06-01

We report on effects of Fe implantation doping-induced changes in structural, optical, morphological, and vibrational properties of cadmium sulfide thin films. Films were implanted with 90 keV Fe+ ions at room temperature for a wide range of fluences from 0.1×1016 to 3.6×1016 ions cm-2 (corresponding to 0.38-12.03 at.% of Fe). Glancing angle X-ray diffraction analysis revealed that the implanted Fe atoms tend to supersaturate by occupying the substitutional cationic sites rather than forming metallic clusters or secondary phase precipitates. In addition, Fe doping does not lead to any structural phase transformation although it induces structural disorder and lattice contraction. Optical absorption studies show a reduction in the optical band gap from 2.39 to 2.17 eV with increasing Fe concentration. This is attributed to disorder-induced band tailing in semiconductors and ion-beam-induced grain growth. The strain associated with a lattice contraction is deduced from micro-Raman scattering measurements and is found that size and shape fluctuations of grains, at higher fluences, give rise to inhomogeneity in strain.

PbSe-Based Colloidal Core/Shell Heterostructures for Optoelectronic Applications

PubMed Central

Zaiats, Gary; Yanover, Diana; Vaxenburg, Roman; Tilchin, Jenya; Sashchiuk, Aldona; Lifshitz, Efrat

2014-01-01

Lead-based (IV–VI) colloidal quantum dots (QDs) are of widespread scientific and technological interest owing to their size-tunable band-gap energy in the near-infrared optical region. This article reviews the synthesis of PbSe-based heterostructures and their structural and optical investigations at various temperatures. The review focuses on the structures consisting of a PbSe core coated with a PbSexS1–x (0 ≤ x ≤ 1) or CdSe shell. The former-type shells were epitaxially grown on the PbSe core, while the latter-type shells were synthesized using partial cation-exchange. The influence of the QD composition and the ambient conditions, i.e., exposure to oxygen, on the QD optical properties, such as radiative lifetime, Stokes shift, and other temperature-dependent characteristics, was investigated. The study revealed unique properties of core/shell heterostructures of various compositions, which offer the opportunity of fine-tuning the QD electronic structure by changing their architecture. A theoretical model of the QD electronic band structure was developed and correlated with the results of the optical studies. The review also outlines the challenges related to potential applications of colloidal PbSe-based heterostructures. PMID:28788244

Radiation properties of two types of luminous textile devices containing plastic optical fibers

NASA Astrophysics Data System (ADS)

Selm, Bärbel; Rothmaier, Markus

2007-05-01

Luminous textiles have the potential to satisfy a need for thin and flexible light diffusers for treatment of intraoral cancerous tissue. Plastic optical fibers (POF) with diameters of 250 microns and smaller are used to make the textiles luminous. Usually light is supplied to the optical fiber at both ends. On the textile surface light emission occurs in a woven structure via damaged straight POFs, whereas the embroidered structure radiates the light out of macroscopically bent POFs. We compared the optical properties of these two types of textile diffusers using red light laser for the embroidery and light emitting diode (LED) for the woven structure as light sources, and found efficiencies for the luminous areas of the two samples of 19 % (woven) and 32 % (embroidery), respectively. It was shown that the efficiency can be greatly improved using an aluminium backing. Additional scattering layers lower the fluence rate by around 30 %. To analyse the homogeneity we took a photo of the illuminated surface using a 3CCD camera and found, for both textiles, a slightly skewed distribution of the dark and bright pixels. The interquartile range of brightness distribution of the embroidery is more than double as the woven structure.

Characterization of AlF3 thin films at 193 nm by thermal evaporation

NASA Astrophysics Data System (ADS)

Lee, Cheng-Chung; Liu, Ming-Chung; Kaneko, Masaaki; Nakahira, Kazuhide; Takano, Yuuichi

2005-12-01

Aluminum fluoride (AlF3) was deposited by a resistive heating boat. To obtain a low optical loss and high laser-induced damage threshold (LIDT) at 193 nm, the films were investigated under different substrate temperatures, deposition rates, and annealing after coating. The optical property (the transmittance, refractive index, extinction coefficient, and optical loss) at 193 nm, microstructure (the cross-sectional morphology, surface roughness, and crystalline structure), mechanical property (stress), and LIDT of AlF3 thin films have been studied. AlF3 thin films deposited at a high substrate temperature and low deposition rate showed a lower optical loss. The highest LIDT occurred at the substrate temperature of 150 °C. The LIDT of the films prepared at a deposition rate of 2 Å/s was higher than that at other deposition rates. The annealing process did not influence the optical properties too much, but it did increase the LIDT and stress.

Characterization of AlF3 thin films at 193 nm by thermal evaporation.

PubMed

Lee, Cheng-Chung; Liu, Ming-Chung; Kaneko, Masaaki; Nakahira, Kazuhide; Takano, Yuuichi

2005-12-01

Aluminum fluoride (AlF3) was deposited by a resistive heating boat. To obtain a low optical loss and high laser-induced damage threshold (LIDT) at 193 nm, the films were investigated under different substrate temperatures, deposition rates, and annealing after coating. The optical property (the transmittance, refractive index, extinction coefficient, and optical loss) at 193 nm, microstructure (the cross-sectional morphology, surface roughness, and crystalline structure), mechanical property (stress), and LIDT of AlF3 thin films have been studied. AlF3 thin films deposited at a high substrate temperature and low deposition rate showed a lower optical loss. The highest LIDT occurred at the substrate temperature of 150 degrees C. The LIDT of the films prepared at a deposition rate of 2 A/s was higher than that at other deposition rates. The annealing process did not influence the optical properties too much, but it did increase the LIDT and stress.

Porous silicon platform for optical detection of functionalized magnetic particles biosensing.

PubMed

Ko, Pil Ju; Ishikawa, Ryousuke; Sohn, Honglae; Sandhu, Adarsh

2013-04-01

The physical properties of porous materials are being exploited for a wide range of applications including optical biosensors, waveguides, gas sensors, micro capacitors, and solar cells. Here, we review the fast, easy and inexpensive electrochemical anodization based fabrication porous silicon (PSi) for optical biosensing using functionalized magnetic particles. Combining magnetically labeled biomolecules with PSi offers a rapid and one-step immunoassay and real-time detection by magnetic manipulation of superparamagnetic beads (SPBs) functionalized with target molecules onto corresponding probe molecules immobilized inside nano-pores of PSi. We first give an introduction to electrochemical and chemical etching procedures used to fabricate a wide range of PSi structures. Next, we describe the basic properties of PSi and underlying optical scattering mechanisms that govern their unique optical properties. Finally, we give examples of our experiments that demonstrate the potential of combining PSi and magnetic beads for real-time point of care diagnostics.

Optical Properties of Metal-Dielectric Structures Based on Photon-Crystal Opal Matrices

NASA Astrophysics Data System (ADS)

Vanin, A. I.; Lukin, A. E.; Romanov, S. G.; Solovyev, V. G.; Khanin, S. D.; Yanikov, M. V.

2018-04-01

Optical properties of novel metal-dielectric nanocomposite materials based on opal matrices have been investigated. The position of optical resonances of nanocomposites, obtained by embedding of silver into the opal matrix by the electrothermodiffusion method, is explained by the Bragg diffraction, and an asymmetric form of resonance curves is attributed to the Fano resonance. An anomalous transmission and absorption of light by hybrid plasmon-photonic layered heterostructures, which is apparently associated with excitation of surface plasmon-polaritons, propagating along "metal-dielectric" interfaces, was revealed.

Microstructure related properties of gadolinium fluoride films deposited by molybdenum boat evaporation

NASA Astrophysics Data System (ADS)

Chang, Y. H.; Wang, C. Y.; Qi, L. Q.; Liu, H.

2017-08-01

In order to optimize the performance of fluoride thin films in wavelength of Deep Ultraviolet (DUV), GdF3 single layers are prepared by thermal evaporation at different deposition temperatures on Fused Silica. Optical and structure properties of each sample are characterized. The results that the refrac-tive index increased gradually and the crystallization status becomes stronger with the temperature rising, the inhomogeneous of the thin films present linearity. The decrease total optical loss with deposited temper-ature is attributed to the higher packing density and lower optical absorption.

Evaluation and correction for optical scattering variations in laser speckle rheology of biological fluids.

PubMed

Hajjarian, Zeinab; Nadkarni, Seemantini K

2013-01-01

Biological fluids fulfill key functionalities such as hydrating, protecting, and nourishing cells and tissues in various organ systems. They are capable of these versatile tasks owing to their distinct structural and viscoelastic properties. Characterizing the viscoelastic properties of bio-fluids is of pivotal importance for monitoring the development of certain pathologies as well as engineering synthetic replacements. Laser Speckle Rheology (LSR) is a novel optical technology that enables mechanical evaluation of tissue. In LSR, a coherent laser beam illuminates the tissue and temporal speckle intensity fluctuations are analyzed to evaluate mechanical properties. The rate of temporal speckle fluctuations is, however, influenced by both optical and mechanical properties of tissue. Therefore, in this paper, we develop and validate an approach to estimate and compensate for the contributions of light scattering to speckle dynamics and demonstrate the capability of LSR for the accurate extraction of viscoelastic moduli in phantom samples and biological fluids of varying optical and mechanical properties.

Evaluation and Correction for Optical Scattering Variations in Laser Speckle Rheology of Biological Fluids

PubMed Central

Hajjarian, Zeinab; Nadkarni, Seemantini K.

2013-01-01

Biological fluids fulfill key functionalities such as hydrating, protecting, and nourishing cells and tissues in various organ systems. They are capable of these versatile tasks owing to their distinct structural and viscoelastic properties. Characterizing the viscoelastic properties of bio-fluids is of pivotal importance for monitoring the development of certain pathologies as well as engineering synthetic replacements. Laser Speckle Rheology (LSR) is a novel optical technology that enables mechanical evaluation of tissue. In LSR, a coherent laser beam illuminates the tissue and temporal speckle intensity fluctuations are analyzed to evaluate mechanical properties. The rate of temporal speckle fluctuations is, however, influenced by both optical and mechanical properties of tissue. Therefore, in this paper, we develop and validate an approach to estimate and compensate for the contributions of light scattering to speckle dynamics and demonstrate the capability of LSR for the accurate extraction of viscoelastic moduli in phantom samples and biological fluids of varying optical and mechanical properties. PMID:23705028

Impact of phytoplankton community structure and function on marine particulate optical properties

NASA Astrophysics Data System (ADS)

McFarland, Malcolm Neil

Phytoplankton are an ecologically important and diverse group of organisms whose distribution, abundance, and population dynamics vary significantly over small spatial (cm) and temporal (minutes) scales in the coastal ocean. Our inability to observe phytoplankton community structure and function at these small scales has severely limited our understanding of the fundamental ecological and evolutionary mechanisms that drive phytoplankton growth, mortality, adaptation and speciation. The goal of this dissertation was to enhance our understanding of phytoplankton ecology by improving in situ observational techniques based on the optical properties of cells, colonies, populations, and communities. Field and laboratory studies were used to determine the effects of phytoplankton species composition, morphology, and physiology on the inherent optical properties of communities and to explore the adaptive significance of bio-optically important cellular characteristics. Initial field studies found a strong association between species composition and the relative magnitude and shape of particulate absorption, scattering, and attenuation coefficient spectra. Subsequent field studies using scanning flow cytometry to directly measure optically important phytoplankton and non-algal particle characteristics demonstrated that the size and pigment content of large (>20 microm) phytoplankton cells and colonies vary significantly with the slope of particulate attenuation and absorption spectra, and with the ratio of particulate scattering to absorption. These relationships enabled visualization of phytoplankton community composition and mortality over small spatial and temporal scales derived from high resolution optical measurements acquired with an autonomous profiling system. Laboratory studies with diverse uni-algal cultures showed that morphological and physiological characteristics of cells and colonies can account for ˜30% of the optical variation observed in natural communities and that complex morphologies and low intracellular pigment concentrations minimize pigment self-shading that could otherwise limit bio-optical fitness. These results demonstrate that optical properties reveal detailed information about the distribution, abundance, morphology, and physiology of phytoplankton that can help explain their ecological dynamics over small spatial scales and the bio-optical function of diverse forms in the ocean.

EUV polarimetry for thin film and surface characterization and EUV phase retarder reflector development.

PubMed

Gaballah, A E H; Nicolosi, P; Ahmed, Nadeem; Jimenez, K; Pettinari, G; Gerardino, A; Zuppella, P

2018-01-01

The knowledge and the manipulation of light polarization state in the vacuum ultraviolet and extreme ultraviolet (EUV) spectral regions play a crucial role from materials science analysis to optical component improvements. In this paper, we present an EUV spectroscopic ellipsometer facility for polarimetry in the 90-160 nm spectral range. A single layer aluminum mirror to be used as a quarter wave retarder has been fully characterized by deriving the optical and structural properties from the amplitude component and phase difference δ measurements. The system can be suitable to investigate the properties of thin films and optical coatings and optics in the EUV region.

Nonequilibrium BN-ZnO: Optical properties and excitonic effects from first principles

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Schleife, André

2018-03-01

The nonequilibrium boron nitride (BN) phase of zinc oxide (ZnO) has been reported for thin films and nanostructures, however, its properties are not well understood due to a persistent controversy that prevents reconciling experimental and first-principles results for its atomic coordinates. We use first-principles theoretical spectroscopy to accurately compute electronic and optical properties, including single-quasiparticle and excitonic effects: Band structures and densities of states are computed using density functional theory, hybrid functionals, and the G W approximation. Accurate optical absorption spectra and exciton binding energies are computed by solving the Bethe-Salpeter equation for the optical polarization function. Using this data we show that the band-gap difference between BN-ZnO and wurtzite (WZ) ZnO agrees very well with experiment when the theoretical lattice geometry is used, but significantly disagrees for the experimental atomic coordinates. We also show that the optical anisotropy of BN-ZnO differs significantly from that of WZ-ZnO, allowing us to optically distinguish both polymorphs. By using the transfer-matrix method to solve Maxwell's equations for thin films composed of both polymorphs, we illustrate that this opens up a promising route for tuning optical properties.

Design and analysis of photonic optical switches with improved wavelength selectivity

NASA Astrophysics Data System (ADS)

Wielichowski, Marcin; Patela, Sergiusz

2005-09-01

Efficient optical modulators and switches are the key elements of the future all-optical fiber networks. Aside from numerous advantages, the integrated optical devices suffer from excessive longitudinal dimensions. The dimensions may be significantly reduced with help of periodic structures, such as Bragg gratings, arrayed waveguides or multilayer structures. In this paper we describe methods of analysis and example of analytical results of a photonic switch with properties modified by the application of periodic change of effective refractive index. The switch is composed of a strip-waveguide directional coupler and a transversal Bragg grating.

Fine structure and optical pumping of spins in individual semiconductor quantum dots

NASA Astrophysics Data System (ADS)

Bracker, Allan S.; Gammon, Daniel; Korenev, Vladimir L.

2008-11-01

We review spin properties of semiconductor quantum dots and their effect on optical spectra. Photoluminescence and other types of spectroscopy are used to probe neutral and charged excitons in individual quantum dots with high spectral and spatial resolution. Spectral fine structure and polarization reveal how quantum dot spins interact with each other and with their environment. By taking advantage of the selectivity of optical selection rules and spin relaxation, optical spin pumping of the ground state electron and nuclear spins is achieved. Through such mechanisms, light can be used to process spins for use as a carrier of information.

First principles study of structural, electronic and optical properties of perovskites CaZrO3 and CaHfO3 in cubic phase

NASA Astrophysics Data System (ADS)

Hoat, D. M.; Silva, J. F. Rivas; Blas, A. Méndez

2018-07-01

In this work, we present the first principles calculations for structural, electronic and optical properties of perovskites CaZrO3 and CaHfO3 using the full-potential linearized augmented plane wave method (FP-LAPW) within the framework of density functional theory (DFT) as implemented in WIEN2k package. The exchange-correlation potential is treated with local density approximation (LDA) and generalized gradient approximation (GGA-PBE and PBESol). Additionally, the Tran Blaha modified Becke-Johnson exchange potential (mBJ) also is employed for electronic and optical calculations due to that it gives very accurate band gap of solids. Our obtained structural parameters are in good agreement with experimental datas and other theoretical results. The energy band gap obtained with mBJ is 4.56 eV for CaZrO3 and 5.27 eV for CaHfO3. The hybridization of states of O atom with those of Zr and Hf atoms in CaZrO3 and CaHfO3, respectively, is observed. The spin-orbit coupling effect on electronic properties of considered compounds also is investigated. Finally, the linear optical properties of CaZrO3 and CaHfO3 are derived from their complex dielectric function calculated with mBJ potential for wide energy range up to 45 eV, and all of them analyzed in details.

New properties of a fiber optic sensor in application of a composite fence for critical infrastructure protection

NASA Astrophysics Data System (ADS)

Zyczkowski, M.; Szustakowski, M.; Markowski, P.

2015-09-01

This paper presents a new solution of using the composite fence with a novel fiber optic modalmetric sensor integrated within its structure. The modalmetric sensor is based on changes in a transverse modal field which is generated at the output of a multimode fiber. By a spatial limitation of the transverse modal field observation to its fragment thereof, changes' transformation in the modal distribution into changes of the output signal amplitude is made. Due to a constant analysis of the structure output signal, detection of an external disorder is possible. Integration of optical fibers with the fence structure allows for an accurate reproduction of the fence movement onto the optical fiber by significantly improving sensitivity of the modalmetric fiber sensor structure.

Understanding the structural, electrical, and optical properties of monolayer h-phase RuO2 nanosheets: a combined experimental and computational study

NASA Astrophysics Data System (ADS)

Ko, Dong-Su; Lee, Woo-Jin; Sul, Soohwan; Jung, Changhoon; Yun, Dong-Jin; Kim, Hee-Goo; Son, Won-Joon; Chung, Jae Gwan; Jung, Doh Won; Kim, Se Yun; Kim, Jeongmin; Lee, Wooyoung; Kwak, Chan; Shin, Jai Kwang; Kim, Jung-Hwa; Roh, Jong Wook

2018-04-01

The structural, electrical, and optical properties of monolayer ruthenium oxide (RuO2) nanosheets (NSs) fabricated by chemical exfoliation of a layered three-dimensional form of K-intercalated RuO2 are studied systematically via experimental and computational methods. Monolayer RuO2 NS is identified as having a distorted h-MX2 structure. This is the first observation of a RuO2 NS structure that is unlike the t-MX2 structure of the RuO2 layers in the parent material and does not have hexagonal symmetry. The distorted h-MX2 RuO2 NSs are shown to have optical transparency superior to that of graphene, thereby predicting the feasibility of applying RuO2 NSs to flexible transparent electrodes. In addition, it is demonstrated that the semiconducting band structures of RuO2 NSs can be manipulated to be semi-metallic by adjusting the crystal structure, which is related to band-gap engineering. This finding indicates that RuO2 NSs can be used in a variety of applications, such as flexible transparent electrodes, atomic-layer devices, and optoelectronic devices.

Optical Vector Near-Field Imaging for the Design of Impedance Matched Optical Antennas and Devices

NASA Astrophysics Data System (ADS)

Olmon, Robert L.

Antennas control and confine electromagnetic energy, transforming free-space propagating modes to localized regions. This is not only true for the traditional classical radio antenna, but also for structures that interact resonantly at frequencies throughout the visible regime, that are on the micro- and nanometer size scales. The investigation of these optical antennas has increased dramatically in recent years. They promise to bring the transformative capabilities of radio antennas to the nanoscale in fields such as plasmonics, photonics, spectroscopy, and microscopy. However, designing optical antennas with desired properties is not straightforward due to different material properties and geometric considerations in the optical regime compared to the RF. New antenna characterization tools and techniques must be developed for the optical frequency range. Here, the optical analogue of the vector network analyzer, based on a scattering-type scanning near-field optical microscope, is described and demonstrated for the investigation of the electric and magnetic properties of optical antennas through their electromagnetic vector near-field. Specifically, bringing this microwave frequency tool to the optical regime enables the study of antenna resonant length scaling, optical frequency electromagnetic parameters including current density and impedance, optical antenna coupling to waveguides and nanoloads, local electric field enhancement, and electromagnetic duality of complementary optical antenna geometries.

Tunable dichroic polarization beam splitter created by one-step holographic photoalignment using four-beam polarization interferometry

NASA Astrophysics Data System (ADS)

Kawai, Kotaro; Sakamoto, Moritsugu; Noda, Kohei; Sasaki, Tomoyuki; Kawatsuki, Nobuhiro; Ono, Hiroshi

2017-01-01

A tunable dichroic polarization beam splitter (tunable DPBS) simultaneously performs the follow functions: 1. Separation of a polarized incident beam into multiple pairs of orthogonally polarized beams; 2. Separation of the propagation direction of two wavelength incident beams after passing through the tunable DPBS; and 3. Control of both advanced polarization and wavelength separation capabilities by varying the temperature of the tunable DPBS. This novel complex optical property is realized by diffraction phenomena using a designed three-dimensional periodic structure of aligned liquid crystals in the tunable DPBS, which was fabricated quickly with precision in a one-step photoalignment using four-beam polarization interferometry. In experiments, we demonstrated that these diffraction properties are obtained by entering polarized beams of wavelengths 532 nm and 633 nm onto the tunable DPBS. These diffraction properties are described using the Jones calculus in a polarization propagation analysis. Of significance is that the aligned liquid crystal structure needed to obtain these diffraction properties was proposed based on a theoretical analysis, and these properties were then demonstrated experimentally. The tunable DPBS can perform several functions of a number of optical elements such as wave plates, polarization beam splitter, dichroic beam splitter, and tunable wavelength filter. Therefore, the tunable DPBS can contribute to greater miniaturization, sophistication, and cost reduction of optical systems used widely in applications, such as optical measurements, communications, and information processing.

Study on the Effect of Various Sol-Gel Concentration to the Electrical, Structural and Optical Properties of the Nanostructured Titanium Dioxide Thin Films

NASA Astrophysics Data System (ADS)

Ahmad, M. K.; Rusop, M.

2009-06-01

Nanostructured Titanium Dioxide (TiO2) thin film with various sol-gel concentration has been successfully prepared using sol-gel spin coating method. The sol-gel concentration of nanostructured TiO2 thin films are varied at 0.1 M, 0.2 M, 0.3 M and 0.4 M, respectively. The effects of different sol-gel concentration of nanostructured TiO2 thin film structural, electrical and optical properties have been studied. The effects of these properties were characterized using X-Ray Diffractometer (XRD), 2-point probe I-V measurement and UV-Vis-NIR Spectrophotometer. For electrical properties, 0.2 M of sol-gel concentration gives the lowest sheet resistance among other concentrated sol-gels. As for structural properties, 0.1 M of concentration gives very weak peak, and continues stronger as in comes to 0.2 M until 0.4 M. It is due to amount of solute (i.e Titanium Isopropoxide) increases in the solution and therefore the intensity of (101) planes become higher. The optical transmission in the visible region (450-1000 nm) for 0.1 M and 0.2 M are the highest (>80%), indicating that the films are transparent in the visible region. The transmission decreases sharply near the ultraviolet region due to the band gap absorption.

Evolution of structural and optical properties of rutile TiO2 thin films synthesized at room temperature by chemical bath deposition method

NASA Astrophysics Data System (ADS)

Mayabadi, A. H.; Waman, V. S.; Kamble, M. M.; Ghosh, S. S.; Gabhale, B. B.; Rondiya, S. R.; Rokade, A. V.; Khadtare, S. S.; Sathe, V. G.; Pathan, H. M.; Gosavi, S. W.; Jadkar, S. R.

2014-02-01

Nanocrystalline thin films of TiO2 were prepared on glass substrates from an aqueous solution of TiCl3 and NH4OH at room temperature using the simple and cost-effective chemical bath deposition (CBD) method. The influence of deposition time on structural, morphological and optical properties was systematically investigated. TiO2 transition from a mixed anatase-rutile phase to a pure rutile phase was revealed by low-angle XRD and Raman spectroscopy. Rutile phase formation was confirmed by FTIR spectroscopy. Scanning electron micrographs revealed that the multigrain structure of as-deposited TiO2 thin films was completely converted into semi-spherical nanoparticles. Optical studies showed that rutile thin films had a high absorption coefficient and a direct bandgap. The optical bandgap decreased slightly (3.29-3.07 eV) with increasing deposition time. The ease of deposition of rutile thin films at low temperature is useful for the fabrication of extremely thin absorber (ETA) solar cells, dye-sensitized solar cells, and gas sensors.