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  • 101.
    Gallas, B.
    et al.
    Inst de NanoSciences de Paris - CNRS, Université Pierre et Marie Curie, France.
    Rivory, J.
    Inst de NanoSciences de Paris - CNRS, Université Pierre et Marie Curie, France.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Vidal, F.
    Inst de NanoSciences de Paris - CNRS, Université Pierre et Marie Curie, France.
    Etgens, V.H.
    Inst de NanoSciences de Paris - CNRS, Université Pierre et Marie Curie, France.
    Changes in optical properties of MnAs thin films on GaAs(001) induced by a- to B-phase transition2008In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 205, no 4, p. 859-862Article in journal (Refereed)
    Abstract [en]

    MnAs layers with 45 nm thickness were grown epitaxially on GaAs(001) substrates. Ellipsometry measurements were made in the spectral range 0.045 eV to 6 eV as a function of temperature (between –10 °C and 50 °C) at 70° of incidence. In this way the transition from the hexagonal α-phase to the orthorhombic β-phase could be monitored. Non-zero off-diagonal elements of the Jones matrix for an azimuth of 38° off the [10] axis of the substrate indicate that the optical functions of MnAs are anisotropic in both phases. The optical conductivity exhibits low-energy interband transitions around 0.3 eV, more clearly seen in the α-phase than in the β-phase. Extrapolation of the optical conductivity to zero frequency confirms that the α-phase is about two times more conducting than the β-phase. A broad structure is observed in the visible range around 3 eV. The α-phase is characterised by an anisotropy induced energy difference of this structure with a maximum at 2.8 eV for the extraordinary index and at 3.15 eV for the ordinary index. This difference vanishes in the β-phase in which anisotropy mainly induces changes in amplitude of the 3 eV structure. The assignment of the structures will be discussed.

  • 102.
    Gallas, B.
    et al.
    Inst des NanoSciences de Paris - CNRS, Université Pierre et Marie Curie, France.
    Rivory, J.
    Inst des NanoSciences de Paris - CNRS, Université Pierre et Marie Curie, France.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Vidal, F.
    Inst des NanoSciences de Paris - CNRS, Université Pierre et Marie Curie, France.
    Stchakovsky, M.
    Thin Film Division, Jobin-Yvon S.A.S. Horiba Group, France.
    Monitoring the a to B-phase transition in MnAs/GaAs(001) thin films as funcion of temperature2008In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 205, no 4, p. 863-866Article in journal (Refereed)
    Abstract [en]

    MnAs layers with a 5 nm thick amorphous GaAs capping layer were grown epitaxially on GaAs(001). Generalized ellipsometric measurements were made on a 45 nm thick layer in the spectral range 1.5–4 eV at temperatures between –10 °C and 50 °C in steps of 5 °C. By using both the diagonal and off-diagonal elements of the Jones matrix, the in-plane unixial anisotropy of MnAs was determined in terms of the ordinary and extraordinary complex dielectric functions. The measurements at each temperature could be well reproduced by modeling using the optical properties of the two limiting phases α-MnAs and β-MnAs determined at –10 °C and 50 °C, respectively. The best sensitivity to the volume fractions of the two phases was obtained near 2.2 eV by monitoring the generalized ellipsometric parameter Δp for which the variations reached 30°.

  • 103.
    Granberg,, Hjalmar
    et al.
    Innventia AB, Stockholm, Sweden.
    Coppel,, Ludovic
    Innventia AB, Stockholm, Sweden.
    Eita, Mohamed
    KTH, Stockholm, Sweden.
    de Mayolo, Eduardo
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Wågberg, Lars
    KTH, Stockholm, Sweden.
    Dynamics of moisture interaction with polyelectrolyte multilayers containing nanofibrillated cellulose2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, p. 496-499Article in journal (Refereed)
    Abstract [en]

    Recent findings have shown that it is possible to use the Layer-by-Layer technique to create nanofibrillated cellulose / polyethyleneimine interference films whose colour change with relative humidity. This study uses different optical models to describe spectral ellipsometry measurements data of interference films and how the film properties alter in dry and humid environments. The results indicate that water condensation initially is filling the surface pores within seconds whereas relaxation of the film to adjust to the added water is a slower process that reaches a steady state after ≈20 min. The maximum swelling ratio of the LbL films is almost independent of the number of layers within the film, but decreases considerably by crosslinking via heat treatment. The films show a distinct birefringence with optical axis perpendicular to the surface. Analysis of the moisture response with different optical models indicates that the films swell uniformly in the thickness direction with no separate water film on top. The results provide important understanding for the design of NFC based LbL films for visual moisture sensors and interactive security paper. 

  • 104. Gustafsson, C
    et al.
    Chen, Jiaxin
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Forsgren, B
    Corrosion Kinetics of Nickel-base Alloys in Simulated BWR Conditions under High Flow Velocity2013Conference paper (Refereed)
    Abstract [en]

    Corrosion-induced material degradation of nickel-base alloys is a critical issue of material integrity and plant operation safety. It is therefore important to determine alloy corrosion rates and to examine corrosion resistant properties of the oxide films formed on the alloy surfaces. This paper contributes to a corrosion kinetic study on nickel-base alloys 82, 182 and 600 in a specially constructed loop system capable of simulating BWR water environments under high flow velocity. The corrosion rate data are derived from measurements of weight changes of test coupons, oxide thicknesses with infrared ellipsometry, and microstructures of oxide films with high resolution electron microscopy. For the alloys examined, corrosion rates decreased with time, suggesting that the formed oxide films were likely protective. Although the overall thicknesses of the oxide films on Alloy 82 and 600 were vastly different from each other, they corroded equally much after nine weeks exposure. Comparing the corrosion rates for Alloys 182 and 600, on the other hand, one finds that the very thick oxide films formed on Alloy 600 did not make the alloy corrode more slowly but more rapidly. These observations indicate that the overall thickness of oxide scales, being largely porous, did not contribute to alloy corrosion protection. The possible rate-limiting step occurring in the inner-most thin but tenacious oxide films at the metal/oxide interface regions is briefly discussed.

  • 105.
    Hollertz, Rebecca
    et al.
    KTH Royal Institute Technology, Sweden.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Faure, Bertrand
    Stockholm University, Sweden.
    Zhang, Yujia
    KTH Royal Institute Technology, Sweden.
    Bergstrom, Lennart
    Stockholm University, Sweden.
    Wagberg, Lars
    KTH Royal Institute Technology, Sweden.
    Dielectric properties of lignin and glucomannan as determined by spectroscopic ellipsometry and Lifshitz estimates of non-retarded Hamaker constants2013In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 4, p. 1639-1648Article in journal (Refereed)
    Abstract [en]

    We present in this study a quantitative estimate of the dispersive interactions between lignin, hemicellulose and cellulose, which are the dominating components in wood and also extensively used to produce paper and packaging materials. The dielectric properties in the UV-visible region of spin-coated films of pure lignin and glucomannan were determined by spectroscopic ellipsometry. The non-retarded Hamaker constants were estimated from the determined spectral parameters using Lifshitz theory for lignin and glucomannan interacting with cellulose, titania and calcium carbonate in vacuum, water and hexane. The Hamaker constants for the different combinations of cellulose, lignin and glucomannan fall within a relatively narrow range of 35–58 and 8–17 zJ, for the values in vacuum (air) and water, respectively. The estimated Hamaker constants for the interactions of the wood components with TiO2 and CaCO3, common additives in paper, in water range from 3 to 19 zJ, thus being similar in magnitude as the interactions between the wood components themselves. In contrast, the Hamaker constant is essentially zero for glucomannan interacting with calcium carbonate in hexane. The Hamaker constants for lignin, hemicellulose and cellulose determined in this study can provide information regarding the surface interactions important for e.g. adhesion, friction, swelling and wetting in paper processing as well as for the resulting behavior of paper products.

  • 106. Isidorsson, J
    et al.
    Giebels, IAME
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Griessen, R
    Optical properties of MgH2 measured in situ by ellipsometry and spectrophotometry2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, no 11Article in journal (Refereed)
    Abstract [en]

    The dielectric properties of alpha-MgH2 are investigated in the photon energy range between 1 and 6.5 eV. For this purpose, a sample configuration and experimental setup are developed that allow both optical transmission and ellipsometric measurements of a transparent thin film in equilibrium with hydrogen. We show that alpha-MgH2 is a transparent, color neutral insulator with a band gap of 5.6+/-0.1 eV. It has an intrinsic transparency of about 80% over the whole visible spectrum. The dielectric function found in this work confirms very recent band-structure calculations using the GW approximation by Alford and Chou (unpublished). As Pd is used as a cap layer we report also the optical properties of PdHx thin films.

  • 107.
    Jansson, Roger
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Zangooie, S
    Linkoping Univ, Dept Phys & Measurement Technol, Appl Phys Lab, SE-58183 Linkoping, Sweden.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Järrendahl, Kenneth
    Linköping University, The Institute of Technology.
    Characterization of 3C-SiC by spectroscopic ellipsometry2000In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 218, no 1, p. R1-R2Article in journal (Refereed)
  • 108.
    Jansson, Roger
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Zangooie, S.
    Center for Microelectronic and Optical Materials Research, Department of Electrical Engineering, University of Nebraska, Lincoln, NE 68588-0511, United States.
    Kugler, T.
    Acreo AB, Interconncet and Packaging, Bredgatan 34, SE-602 21 Norrköping, Sweden.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Optical and microstructural characterization of thin films of photochromic fulgides2001In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 62, no 7, p. 1219-1228Article in journal (Refereed)
    Abstract [en]

    Variable angle spectroscopic ellipsometry has been used for determining the optical properties, in terms of the complex dielectric function in the near UV-VIS-near IR spectral range, and the thicknesses of thin fulgide films of type E-a-(2,5-dimethyl-3-furyl)-ethylidene(adamantylidene)succinic anhydride and (E)-2-[a-(2,5-dimethyl-3-thienyl)ethylidene]-3-isopropylidenesuccinic anhydride. The films had thicknesses in the range 28-40 nm and were spin coated onto silicon substrates. To simultaneously extract film thicknesses and optical properties of the films, several methods of analysis were employed in order to decrease correlation between the fitting parameters in the optical model of the structure. In agreement with previous absorbance measurements done by others on similar materials in liquid or solid form, it was found that the fulgides studied have several resonances in the wavelength region below 400 nm and that new resonances appear in the middle of the visible region upon UV exposure. The ellipsometric analysis, as well as atomic force microscopy studies, showed that the films were very smooth with a root mean square surface roughness <0.4 nm and that a small thickness change of the film takes place upon UV exposure. Furthermore, AFM studies revealed that large phase changes take place when the samples are stored in darkness for several days, indicating that the materials are not stable in thin film form. © 2001 Elsevier Science Ltd.

  • 109. Johansen, K
    et al.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Imaging surface plasmon resonance sensor based on multiple wavelengths: Sensitivity considerations2000In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 71, no 9, p. 3530-3538Article in journal (Refereed)
    Abstract [en]

    A new, multiple wavelength surface plasmon resonance apparatus for imaging applications is presented. It can be used for biosensing, e.g., for monitoring of chemical and biological reactions in real time with label-free molecules. A setup with a fixed incident angle in the Kretschmann configuration with gold as the supporting metal is described, both theoretically and experimentally. Simulations of the sensor response based on independently recorded optical (ellipsometric) data of gold show that the sensitivity for three-dimensional recognition layers (bulk) increases with increasing wavelength. For two-dimensional recognition layers (adlayer) maximum sensitivity is obtained within a limited wavelength range. In this situation, the rejection of bulk disturbances, e.g., emanating from temperature variations, decreases, with increasing wavelength. For imaging surface plasmon resonance the spatial resolution decreases with increasing wavelength. Hence, there is always a compromise between spatial resolution, bulk disturbance rejection, and sensitivity. Most importantly, by simultaneously using multiple wavelengths, it is possible to maintain a high sensitivity and accuracy over a large dynamic range. Furthermore, our simulations show that the sensitivity is independent of the refractive index of the prism. (C) 2000 American Institute of Physics. [S0034-6748(00)02909-9].

  • 110.
    Johansson, Malin B.
    et al.
    Uppsala University, Sweden .
    Baldissera, Gustavo
    Royal Institute of Technology KTH, Stockholm, Sweden .
    Valyukh, Iryna
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Persson, Clas
    Royal Institute of Technology KTH, Stockholm, Sweden .
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Niklasson, Gunnar A.
    Uppsala University, Sweden .
    Osterlund, Lars
    Uppsala University, Sweden .
    Electronic and optical properties of nanocrystalline WO3 thin films studied by optical spectroscopy and density functional calculations2013In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 25, no 20, p. 205502-Article in journal (Refereed)
    Abstract [en]

    The optical and electronic properties of nanocrystalline WO3 thin films prepared by reactive dc magnetron sputtering at different total pressures (P-tot) were studied by optical spectroscopy and density functional theory (DFT) calculations. Monoclinic films prepared at low P-tot 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 E-g approximate to 3.1 eV, which increase with increasing P-tot by 0.1 eV, and correlate with the structural modifications of the films. The electronic structures of triclinic delta-WO3, and monoclinic gamma- and epsilon-WO3 were calculated using the Green function with screened Coulomb interaction (GW approach), and the local density approximation. The delta-WO3 and gamma-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 (andgt;3 eV) and allowed transitions (andgt;3.8 eV). The calculations show that E-g in epsilon-WO3 is higher than in the delta-WO3 and gamma-WO3 phases, which provides an explanation for the P-tot dependence of the optical data.

  • 111.
    Johansson, Å. A.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hjörvarsson, B.
    Dept. of Physics, Royal Institute of Technology, Stockholm, Sweden.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Intrinsic, n- and p-doped a-Si:H thin films grown by DC magnetron sputtering with doped targets1999In: Materials Research Society Symposium Proceedings, ISSN 0272-9172, E-ISSN 1946-4274, Vol. 557, p. 31-36Article in journal (Refereed)
    Abstract [en]

    Intrinsic, n- and p-type a-Si:H films were deposited by dc magnetron sputtering and analyzed with several techniques. The films were synthesized in a reactive Ar-Ha atmosphere giving H contents in the range of 3-20 at %. The films were sputtered from pure silicon targets and doped silicon targets with 1 at % B or P. Doping by co-sputtering from composite Si/B4C targets was also explored. The doping concentrations were 3 × 1020 - 2 × 1021 cm-3 for the p-type films and 2.6-2.9 × 1019cm-3 for the n-type films. The conductivity was in the range lO'MO"4 cm-1 for p-doped films and 10-5 Cl cm-1 for the best n-doped films. Band gap estimations were obtained from dielectric function data and showed an increase with hydrogen content. A comparison to device quality PECVD-samples was also made.

  • 112.
    Johs, Blaine
    et al.
    JA Woollam Co Inc, USA.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Wagner, Thomas
    LOT Oriel GmbH and Co KG, Germany.
    Appel, David
    LOT Oriel GmbH and Co KG, Germany.
    Peros, Dimitrios
    ALANOD Aluminium-Veredlung GmbH & Co. KG, Germany.
    Accuracy of color determination from spectroscopic ellipsometry measurements2011In: THIN SOLID FILMS, ISSN 0040-6090, Vol. 519, no 9, p. 2711-2714Article in journal (Refereed)
    Abstract [en]

    In many coating and display applications, quantitative determination of the sample color is required. Standard procedures exist for converting an experimentally measured reflectivity spectrum into color coordinates such as CIE L*a*b*. In this paper we evaluate CIE L*a*b* color coordinates using a reflectivity spectrum which is calculated from an optical model determined by a spectroscopic ellipsometry (SE) analysis of the sample. The accuracy of the SE-determined color coordinates are compared with traditional color measurements, and the advantages of using SE for color determination are discussed.

  • 113.
    Järrendahl, Kenneth
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Polarizing Natural Nanostructures2014In: Ellipsometry of Functional Organic Surfaces and Films / [ed] Hinrichs, Karsten; Eichhorn Klaus-Jochen, Springer Berlin/Heidelberg, 2014, p. 155-169Chapter in book (Refereed)
    Abstract [en]

    A brief description of the polarizing environment we are living in and the possibilities for some animals to detect this polarization is made. This is followed by a presentation of how animals and plants generate polarized light, usually through reflection from micro- and nanostructures. Special attention is made to scarab beetles reflecting light with a high degree of circular polarization. Finally some comments on the biological aspects of polarization are made.

  • 114.
    Järrendahl, Kenneth
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Berlind, Torun
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Gustafson, Johan L.I.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Fernández del Río, Lia
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Polarization of Light Reflected from Chiral Structures - Calculations Compared with Mueller Matrix Ellipsometry Measurements on Natural and Synthetic Samples2012Conference paper (Other academic)
    Abstract [en]

    The Mueller matrix elements mij representing the polarization response from a nanostructured materialis determined by the constituent materials optical properties and the superstructure. Here, we investigate how chiral structures in form of helicoidally stacked uniaxial layers determine mij as a functionof polarization state, wavelength, incidence angle and azimuthal angle of the incoming light. The studied parameters include the layer materials ordinary/extraordinary optical properties, Euler angle values, and layer thickness as well as the thickness and pitch of the helicoidal superstructure. Sub- and superstructure inhomogeneity is also introduced. From the Fresnel-based calculations, mij aswell as the degree of polarization, ellipticity and azimuth of the polarization ellipse are obtained and presented as contour and trace plots to give a complete view of the polarization behavior. The results from the calculations are compared with Mueller matrix spectroscopic ellipsometry measurements of both natural and synthesized helicoidal structures. The measurements were performed with a dualrotating compensator system (RC2, J.A. Woollam Co., Inc.) for wavelengths in the range from 245 to 1000 nm and incident angles from 20 to 75°. For some measurements the azimuthal angle of the incident light was varied. The investigated natural chiral structures were exoskeletons from several beetles in the scarab subfamilies Cetoniinae and Rutelinae. As predicted from the calculations it isobserved that the reflection from these beetles can have a high degree of polarization and high ellipticity (near-circular polarization). Both left- and right-polarization was observed. The synthesized structures are helicoidal nanorods of Al1−xInxN grown on sapphire substrates with metal-nitride seedlayers using UHV magnetron sputtering. Due to an internal composition gradient (a variation of x) in the crystalline structure, the nanorods will tilt away from the substrate normal. Helicoidal structures can thus be obtained by rotating the substrate around its normal during deposition. Samples with different pitch and layer thickness with right-handed as well as left-handed chirality were grown. Also for these structures both left and right near-circular polarized light is observed. By combining calculations, ellipsometry measurements and scanning electron microscopy characterization we get agood input to build layered models of the natural and synthetic samples. After regression fitting agood agreement between calculated and measured optical data were obtained.

  • 115.
    Järrendahl, Kenneth
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Ecology . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Mueller-Matrix Ellipsometry Studies of Optically Active Structures in Scarab2009Conference paper (Other academic)
  • 116.
    Järrendahl, Kenneth
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Ecology. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Mueller-Matrix Ellipsometry Studies of Optically Active Structures in Scarab Beerles (conf. France)2009Conference paper (Other academic)
  • 117.
    Järrendahl, Kenneth
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Ecology . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Mueller-Matrix Ellipsometry Studies of Optically Active Structures in Scarab Beetles2009Conference paper (Other academic)
  • 118.
    Karlsson, L M
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Tengvall, Pentti
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Adsorption of human serum albumin in porous silicon gradients2003Conference paper (Other academic)
    Abstract [en]

    Backside etching has been utilized to produce gradients of pore size and layer thickness in porous silicon. Human serum albumin (HSA) was adsorbed on such gradients at two different pH values: 4.9, the pI of HSA, and 7.4, the physiological pH. The samples were investigated by scanning electron microscopy, spectroscopic ellipsometry, and autoradiography. The results show that the protein adsorbed displays a gradient along with the pore size and the thickness gradient. The higher than current density used during etching, the more sway-back shaped curves were seen for the protein adsorption pattern, independent of pH. When 50 mA/cm2 current density was used during etching, the quota between the maximal intensity value and the plateau value seen after adsorption of the HSA increased for pH 7.4.

  • 119.
    Karlsson, L M
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Tengvall, Pentti
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Back-side etching A tool for making morphology gradients in porous silicon2002In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 149, no 12Article in journal (Refereed)
    Abstract [en]

    A new method for preparing morphology gradients in electrochemically etched porous silicon layers in presented. The idea is to etch on the back side of the anode and thus utilize and inhomogenous electric field to control the pore size along a surface. The etching procedure resulted in a complex gradient in pore size, porosity, and porous layer thickness, which was studied by spectroscopic ellipsometry and scanning electron microscopy. The gradients are of interest, e.g., for biomaterials research, bio-sensor applications, and for basic studies of adsorption of organic molecules, like proteins. In order to investigate the potential of the gradient surfaces for protein adsorption studies, these were exposed to human serum albumin, and a gradient in the amount of adsorbed protein was observed.

  • 120.
    Karlsson, L M
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Tengvall, Pentti
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Penetration and loading of human serum albumin in porous silicon layers with different pore sizes and thicknesses2003In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 266, no 1, p. 40-47Article in journal (Refereed)
    Abstract [en]

    Human serum albumin was adsorbed into porous silicon layers with thickness up to 3 µm and with different mean pore radius in the range 4.5-10 nm. The adsorbed amount of protein was quantified by I125 radioactive labeling techniques and ellipsometry. The results show that albumin penetrated into the pores when the mean pore radius was larger than 5.5 nm, but could not totally occupy the available surface area when the layer thickness was larger than 1 µm. Loading of albumin both into porous layers and onto plane silicon as a function of albumin concentration was also investigated. These measurements show that loading of protein increased with protein concentration at least up to 10 mg/ml for porous silicon and up to 1 mg/ml for plane silicon. The maximum deposition into the type of porous layers used here was 28 µg/cm2, compared to 0.36 µg/cm2 for plane silicon. © 2003 Elsevier Inc. All rights reserved.

  • 121.
    Karlsson, Linda
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Schubert, Mattias
    Institute for Experimental Physics II University of Leipzig, Germany.
    Ashkenov, N.
    Institute for Experimental Physics II University of Leipzig, Germany.
    Adsorption of human serum albumin in porous silicon gradients monitored by spatially-resolved spectroscopic ellipsometry2005In: Physica status solidi, ISSN 0031-8957, Vol. 2, p. 3293-3297Article in journal (Refereed)
  • 122.
    Karlsson, Linda
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics.
    Scubert, Mattias
    Inst for Experimental Physics II University of Leipzig.
    Ashkenov, N.
    Inst for Experimental Physics II University of Leipzig.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics.
    Protein adsorption in porous silicon gradients monitored by spatially-resolved spectroscopic ellipsometry2004In: Elsevier Science, ISSN 1626-3200, Vol. 455-456, p. 726-730Article in journal (Refereed)
    Abstract [en]

    Porous silicon layers with a one-dimensional lateral gradient in pore size are prepared by electrochemical etching and characterized by spectroscopic ellipsometry in the visible to near-infrared region. The ellipsometer is equipped with a micro-spot option giving a lateral resolution of approximately 100 μm. By matching multiple-layer-model calculations to the laterally-resolved variable angle of incidence spectroscopic ellipsometry data, the thickness variation along the gradient as well as the in-depth porosity profile is mapped. Upon exposure to a protein solution, protein adsorption occurs on top of the porous silicon layer. At the high-porosity region of the gradient also penetration of protein molecules into the porous layer takes place. Ellipsometry data are recorded after protein exposure and variations of protein adsorption along the porous silicon gradient is modeled as well as the in-depth profile of protein penetration.

  • 123. Karpus, V.
    et al.
    Babonas, G-J.
    Reza, A.
    Tumenas, S.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Wassmus, NN
    Brühne, S.
    Optical responce of si-ZnMgHo quasicrystal2008In: 10th International Conference on Quasicrystals,2008, Zürich: ETH , 2008Conference paper (Refereed)
  • 124.
    Karpus, V.
    et al.
    Centre Phys Science and Technology, Lithuania.
    Tumenas, S.
    Centre Phys Science and Technology, Lithuania.
    Eikevicius, A.
    Centre Phys Science and Technology, Lithuania.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Interband optical transitions of Zn2016In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 253, no 3, p. 419-428Article in journal (Refereed)
    Abstract [en]

    Experimental results of an optical study of single-crystal zinc are presented. Components of the Zn dielectric function tensor were measured by spectroscopic ellipsometry in the 0.1-5 eV spectral range. In the NIR-VIS range, the dielectric function spectra show two clearly resolved, polarization-dependent optical features located at about 1 and 1.7 eV. The optical features were analyzed in a framework of parallel-band optical transitions. The performed theoretical calculations of the optical conductivity spectra well reproduce the experimental data with respect to positions, intensities, and polarization dependencies of the observed interband absorption peaks. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • 125.
    Karpus, V
    et al.
    Institute Semicond Phys, Lithuania.
    Tumenas, S
    Institute Semicond Phys, Lithuania.
    Suchodolskis, A
    Institute Semicond Phys, Lithuania.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Assmus, W
    Goethe University of Frankfurt, Germany.
    Optical spectroscopy and electronic structure of the face-centered icosahedral quasicrystals Zn-Mg-R (R=Y, Ho, Er)2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, no 9Article in journal (Refereed)
    Abstract [en]

    Results of optical spectroscopy studies of the face-centered icosahedral (fci) single-grain Zn-Mg-Y, Zn-Mg-Ho, and Zn-Mg-Er quasicrystals (QCs) are presented. The dielectric function of the QCs was measured in the 0.01–6 eV spectral range by IR-UV spectroscopic ellipsometry and far infrared reflection spectroscopy techniques. A theoretical scheme of optical conductivity calculations is extended to account for the Fermi level positions within and below a pseudogap. The model of the QC electron energy spectrum, based on a band structure hypothesis, is suggested, which treats the electronic subsystem as a nearly free electron gas affected by intersections of the Fermi surface with several families of Bragg planes. The experimental optical spectra are reproduced in detail by theoretical calculations carried out within the framework of the model. The parameters of the electron energy spectrum deduced from an analysis of optical data are close to those previously determined in an analysis of fci Zn-Mg-R valence band photoemission spectra.

  • 126.
    Karpus, Vytautas
    et al.
    Institute for Semiconductor Physics, Lithuania.
    Babonas, Gintautas-Jurgis
    Institute for Semiconductor Physics, Lithuania.
    Reza, Alfonsas
    Institute for Semiconductor Physics, Lithuania.
    Tumenas, Saulius
    Institute for Semiconductor Physics, Lithuania.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Assmus, Wolf
    University of Frankfurt.
    Bruehne , Stefan
    University of Frankfurt.
    Optical response of si-ZnMgHo quasicrystal2009In: ZEITSCHRIFT FUR KRISTALLOGRAPHIE, ISSN 0044-2968 , Vol. 224, no 1-2, p. 39-41Article in journal (Refereed)
    Abstract [en]

    The results of room-temperature optical study of single-grain simple icosahedral ZnMgHo quasicrystals are presented. The dielectric function epsilon(omega) of the quasicrystals was measured by spectroscopic ellipsometry technique in the spectral range of 0.1 - 7 eV. The si-ZnMgHo optical response is a superposition of the free-electron Drude-type contribution and that of the interband transitions. The experimental epsilon(omega) spectra are well simulated within a framework of the band structure hypothesis. The deduced parameters of the si-ZnMgHo electron energy spectrum are close to their values determined previously in an analysis of the si-ZnMgHo photoemission data.

  • 127.
    Lansåker, Pia
    et al.
    Uppsala University, Uppsala, Sweden.
    Tuncer, Enis
    3M Austin Center, Austin, USA.
    Valyukh, Iryna
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Niklasson, Gunnar
    Uppsala University, Uppsala, Sweden.
    Granqvist, Claes Göran
    Uppsala University, Uppsala, Sweden.
    Spectral  density analysis of thin gold films: Thickness and structure dependence of the optical properties2013In: Proceedings, ISSN 0351-6067, p. 443-447Article, book review (Other academic)
    Abstract [en]

    In this paper we study the feasibility of representing the optical properties of ultrathin gold films by effective medium theories. Gold films with mass thicknesses in the range of 1.4 to 9.2 nm were deposited by DC magnetron sputtering onto non-heated glass substrates. Optical measurements in the range 0.25 to 2 µm were carried out by spectroscopic ellipsometry, and the effective complex dielectric function of each film was determined. The gold films were modelled as a mixture of gold and air, and a general effective medium description using the spectral density function (SDF) was used to describe their optical properties. Numerical inversion of the experimental dielectric function gave a broad and rather featureless SDF with a few superimposed peak structures, both for island structures and percolating films. The broad background is qualitatively similar to the predictions of the Bruggeman [Ann. Phys. (Leipzig), 5th series, 24 (1935) 636-679] model.

  • 128.
    Levin, Martina
    et al.
    Naphtenics Research AB Nynäs Petroleum.
    Wiklund, Per
    Naphtenics Research AB Nynäs Petroleum.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Adsorption and film growth of N-methylamino substituted triazoles on copper surfaces in dydrocarbon media2007In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 254, p. 1528-1533Article in journal (Refereed)
  • 129.
    Lindquist, OPA
    et al.
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Forsberg, Urban
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Bergman, JP
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
    Järrendahl, Kenneth
    Linköping University, The Institute of Technology.
    Optical characterization of 4H-SiC by variable angle of incidence spectroscopic ellipsometry2000In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 338-3, p. 575-578Article in journal (Refereed)
    Abstract [en]

    A variable angle of incidence spectroscopic ellipsometer equipped with a compensator has been used to determine the dielectric functions in the 0.74 - 6 eV photon energy range of n-type bulk 4H-SiC with doping concentrations between 10(17) and 10(19) cm(-3). The resulting dielectric function for different SiC wafers depends on the doping concentration, especially around the absorption onset and higher photon energies. Measurements on different wafers with the same doping show good reproducibility. Simulations and preliminary measurements show that ellipsometry might be useful for thickness determination of thin (<1 m) homoepitaxial films.

  • 130. Lindquist, OPA
    et al.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Henry, Anne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Järrendahl, Kenneth
    Linköping University, The Institute of Technology.
    Infrared optical properties of 3C, 4H and 6H silicon carbide2003In: Materials Science Forum, Vols. 433-436, 2003, Vol. 433-4, p. 329-332Conference paper (Refereed)
    Abstract [en]

    Dielectric functions for 3C-, 4H- and 6H-silicon carbide in the infrared photon energy region have been obtained using spectroscopic ellipsometry. Using samples with the optic axes both parallel and perpendicular to the sample surface normal, both the ordinary and extra-ordinary dielectric function were probed. Phonon modes and optical anisotropy are shown in the dielectric spectra.

  • 131.
    Lindquist, O.P.A.
    et al.
    IFM Linköpings universitet.
    Schubert, Mattias
    Inst for Experimental Physics II University of Leipzig.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Järrendahl, Kenneth
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Infrared to vacuum ultraviolet optical properties of 3C, 4H and 6H silicon carbide measured by spectroscopic ellipsometry2004In: Elsevier Science, ISSN 1626-3200, Vol. 455-456, p. 235-238Article in journal (Refereed)
  • 132.
    Magnusson, Roger
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Garcia-Caure, Enric
    LPICM, CNRS, Ecole Polytechnique, Université Paris–Saclay, Palaiseau, France.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Ossikovski, Razvigor
    LPICM, CNRS, Ecole Polytechnique, Université Paris–Saclay, Palaiseau, France.
    Sum regression decomposition of spectral and angle-resolved Mueller-matrices from biological reflectors2016In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, no 15, p. 4060-4065Article in journal (Refereed)
    Abstract [en]

    In this report we present studies on beetles of the Scarabaeidae family. The selected beetles show brilliant colors and in addition interesting polarization features. Mueller matrices of such beetles are of large interest to explore for biomimetics and for the understanding of the biological relevance of the observed polarization phenomena. Several species of the Scarabaeidae family have been studied by Hodgkinson, Goldstein  and our group to mention some. Ellipticity, degree of polarization and other derived parameters have been reported and Arwin et al. also did optical modeling to determine structural parameters of the scutellum part of the exoskeleton of Cetonia aurata. Mueller matrices are very rich in information about the sample properties and can also be analyzed by addressing depolarization. Cloude showed that a depolarizing Mueller matrix can be represented by a sum of up to four non-depolarizing Mueller matrices weighted by the eigenvalues of the covariance matrix of the Mueller matrix. These eigenvalues are all positive for a physically realizable Mueller matrix and this, so called sum decomposition can be used to filter matrices and obtain a measure of experimental fidelity. The result of the decomposition can also be used to describe a Mueller matrix as a set of basic optical elements having direct physical meaning, such as polarizers and retarders. Pioneering work on decomposition of Mueller-matrix images, including studies of beetles, was performed by Ossikovski et al. We have also previously demonstrated this with Cloude as well as regression decomposition of Mueller matrix spectra and images measured at near-normal incidence on C. aurata. Using Cloude decomposition we found that the experimentally determined Mueller matrix of C. aurata decomposes into a set of a mirror and a circular polarizer. Those results were then the basis for a more stable regression decomposition where the result was confirmed.

  • 133.
    Magnusson, Roger
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    InxAl1-xN chiral nanorods mimicking the polarization features of scarab beetles2015In: SPIE Proceedings Vol. 942: Bioinspiration, Biomimetics, and Bioreplication 2015 / [ed] Akhlesh Lakhtakia, Mato Knez, Raúl Martín-Palma, SPIE - International Society for Optical Engineering, 2015, Vol. 9429, p. 94290A-1-94290A-8Conference paper (Refereed)
    Abstract [en]

    The scarab beetle Cetonia aurata is known to reflect light with brilliant colors and a high degree of circular polarization. Both color and polarization effects originate from the beetles exoskeleton and have been attributed to a Bragg reflection of the incident light due to a twisted laminar structure. Our strategy for mimicking the optical properties of the Cetonia aurata was therefore to design and fabricate transparent, chiral films. A series of films with tailored transparent structures of helicoidal InxAl1-xN nanorods were grown on sapphire substrates using UHV magnetron sputtering. The value of x is tailored to gradually decrease from one side to the other in each nanorod normal to its growth direction. This introduces an in-plane anisotropy with different refractive indices in the direction of the gradient and perpendicular to it. By rotating the sample during film growth the in-plane optical axis will be rotated from bottom to top and thereby creating a chiral film. Based on Muellermatrix ellipsometry, optical modeling has been done suggesting that both the exoskeleton of Cetonia aurata and our artificial material can be modeled by an anisotropic film made up of a stack of thin layers, each one with its in-plane optical axis slightly rotated with respect to the previous layer. Simulations based on the optical modeling were used to investigate how pitch and thickness of the film together with the optical properties of the constitutive materials affects the width and spectral position of the Bragg reflection band.

  • 134.
    Magnusson, Roger
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Optical Mueller Matrix Modeling of Chiral AlxIn1-xN Nanospirals2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 571, p. 447-452Article in journal (Refereed)
    Abstract [en]

    Metamaterials in the form of chiral nanostructures have shown great potential for applications such as chemical and biochemical sensors and broadband or wavelength tunable circular polarizers. Here we demonstrate a method to produce tailored transparent chiral nanostructures with the wide-bandgap semiconductor AlxIn1 − xN. A series of anisotropic and transparent films of AlxIn1 − xN were produced using curved-lattice epitaxial growth on metallic buffer layers. By controlling the sample orientation during dual magnetron sputter deposition, nanospirals with right-handed or left-handed chirality were produced. Using a dual rotating compensator ellipsometer in reflection mode, the full Mueller matrix was measured in the spectral range 245–1700 nm at multiple angles of incidence. The samples were rotated one full turn around their normal during measurements to provide a complete description of the polarization properties in all directions. For certain wavelengths, unpolarized light reflected off these films becomes highly polarized with a polarization state close to circular. Nanostructured films with right- and left-handed chirality produce reflections with right- and left-handed near-circularly polarized light, respectively. A model with a biaxial layer in which the optical axes are rotated from bottom to top was fitted to the Mueller-matrix data. Hence we can perform non-destructive structural analysis of the complex thin layers and confirm the tailored structure. In addition, the refractive index, modeled with a biaxial Cauchy dispersion model, is obtained for the AlxIn1 − xN films.

  • 135.
    Magnusson, Roger
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Chiral nanostructures producing near circular polarization2014In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 4, no 7, p. 1389-1403Article in journal (Refereed)
    Abstract [en]

    Optical properties of chiral nanostructured films made of Al1-xInxN using a new growth mechanism - curved-lattice epitaxial growth - are reported. Using this technique, chiral films with right- and left-handed nanospirals were produced. The chiral properties of the films, originating mainly from an internal anisotropy and to a lesser extent from the external helical shape of the nanospirals, give rise to selective reflection of circular polarization which makes them useful as narrow-band near-circular polarization reflectors. The chiral nanostructured films reflect light with high degree of circular polarization in the ultraviolet part of the spectrum with left- and right-handedness depending on the handedness of the nanostructures in the films.

  • 136.
    Magnusson, Roger
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Ossikovski, Razvigor
    LPICM, CNRS, Ecole Polytechnique, Université Paris - Saclay, Palaiseau, France.
    Garcia-caurel, Enric
    LPICM, CNRS, Ecole Polytechnique, Université Paris - Saclay, Palaiseau, France.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Decomposition of angle resolved spectroscopic Mueller matrices from Scarabaeidae beetles2015Conference paper (Other academic)
    Abstract [en]

    We use angle-dependent Mueller-matrix spectroscopic ellipsometry (MMSE) to determine Mueller matrices of Scarabaeidae beetles which show fascinating reflection properties due to structural phenomena in the exocuticle which are often depolarizing. It has been shown by Cloude [1] that a depolarizing matrix can be decomposed into a sum of up to four non-depolarizing matrices according to M= aM­­1+bM2+cM3+dM4, where a, b, c and d are eigenvalues of the covariance matrix of M. Using the same eigenvalues the matrices Mi can be calculated. This method provides the full solution to the decomposition with both the non-depolarizing matrices and the weight of each of them in the sum.

    An alternative to Cloude decomposition is regression decomposition. Here any Mueller matrix can be decomposed into a set of matrices Mi which are specified beforehand. Whereas in Cloude decomposition the only constraint on the matrices is that they are physically realizable non-depolarizing Mueller matrices, we can now limit the constraint and only use Mueller matrices representing pure optical devices having direct physical meaning, such as polarizers, retarders, etc. This leaves a, b, c, d as fit parameters to minimize the Frobenius norm Mexp -Mreg where Mexp is the experimentally determined Mueller matrix to be decomposed and Mreg is the sum of all Mi. Depending on Mexp an appropriate choice of Mreg matrices has to be made and different values of a, b, c and d are obtained through regression analysis.

    We have previously shown that regression decomposition can be used to show that the Mueller matrix of Cetonia aurata can be decomposed into a sum of a circular polarizer and a mirror [2]. Here we expand the analysis to include angle-resolved spectral Mueller matrices, and also include more species of Scarabaeidae beetles.

    One effect of the decomposition is that when depolarization is caused by an inhomogeneous sample with regions of different optical properties the Mueller matrices of the different regions can be retrieved under certain conditions. Regression decomposition also has potential to be a classification tool for biological samples where a set of standard matrices are used in the decomposition and the parameters a, b, c, d are used to quantify the polarizing properties of the sample.

    [1] Cloude S.R. 1989. Conditions for the physical realisability of matrix operators in polarimetry. Proc. SPIE 1166, Polarization Considerations for Optical Systems II, pp. 177-185

    [2] Arwin H, Magnusson R, Garcia-Caurel E, Fallet C, Järrendahl K, De Martino A, Ossikovski R, 2015. Sum decomposition of Mueller-matrix images and spectra of beetle cuticles. Opt. Express, vol. 23, no. 3, pp. 1951–1966

  • 137.
    Magnusson, Roger
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Rehammar, Robert
    Göteborg University.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Lattices of Freestanding Carbon Nanofibres Characterized by Spectroscopic Ellipsometry2009Conference paper (Other academic)
    Abstract [en]

    Photonic crystals with lattice constant in the visible range of light can be fabricated using freestanding carbon nanofibres. These types of structures are optically complicated, with geometric effects both from the lattice and from individual scatterers. In this report, results from pilot studies of the optical properties of such samples are presented.

    Ellipsometric measurements on samples with vertically aligned arrays of free-standing carbon nanofibres with lengths up to 1600 nm are presented. The carbon nanofibres were grown on silicon wafers with a 70 nm layer of titanium and a 15 nm layer of titanium nitride using plasma-CVD with nickel as catalyst. Electron beam lithography was used to create the nanofibre lattice. Samples with varying periodicity and length of the carbon fibers, i.e. film thickness, were investigated.

    In this pilot study measurements were performed with a dual rotating compensator ellipsometer in the spectral range 245-1700 nm. The instrument provides the full Mueller matrix of the sample and measurements were performed at multiple angles of incidence and different sample orientations.

    The samples show no difference in the optical response when rotated 90°, but at other orientations changes in the spectrum are observed below a wavelength of approximately 1000 nm. The analysis of the ellipsometric data is presented and different modeling approaches are discussed.

  • 138.
    Mendoza, Arturo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology. Cinvestav-Querétaro, Mexico.
    Muñoz-Pineda, Eloy
    Cinvestav-Querétaro, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Evidence for a dispersion relation of optical modes in the cuticle of the scarab beetle Cotinis mutabilis2014In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 4, no 12, p. 2484-2496Article in journal (Refereed)
    Abstract [en]

    Variable angle Mueller matrix spectroscopic ellipsometry is used to study the properties of light reflected from the exoskeleton (cuticle) of the scarab beetle Cotinis mutabilis. For unpolarized incident light, the ellipticity and degree of polarization of the reflected light reveal a lefthanded helical structure in the beetle cuticle. Analysis of the spectral position of the maxima and minima in the interference oscillations of the Mueller-matrix elements provides evidence for a dispersion relation similar to that of optical modes in chiral nematic liquid crystals calculated within a two-wave approximation. Additionally, a structural model for the cuticle of C. mutabilis is derived from the properties of the optical modes for nonattenuated propagation or selective reflection.

  • 139.
    Mendoza-Galvan, A.
    et al.
    Cinvestav-IPN, Unidad Querétaro, Querétaro, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Dmitriev, A.
    Department of Applied Physics, Chalmers University of Technology, Göteborg.
    Pakizeh, T.
    Faculty of Electrical and Computer Engineering, K. N. Toosi University of Technology, Tehran, Iran.
    Käll, M.
    Department of Applied Physics, Chalmers University of Technology, Göteborg.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Optical response of supported gold nanodisks2011In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 19, no 13, p. 12093-12107Article in journal (Refereed)
    Abstract [en]

    It is shown that the ellipsometric spectra of short range ordered planar arrays of gold nanodisks supported on glass substrates can be described by modeling the nanostructured arrays as uniaxial homogeneous layers with dielectric functions of the Lorentz type. However, appreciable deviations from experimental data are observed in calculated spectra of irradiance measurements. A qualitative and quantitative description of all measured spectra is obtained with a uniaxial effective medium dielectric function in which the nanodisks are modeled as oblate spheroids. Dynamic depolarization factors in the long-wavelength approximation and interaction with the substrate are considered. Similar results are obtained calculating the optical spectra using the island-film theory. Nevertheless, a small in-plane anisotropy and quadrupolar coupling effects reveal a very complex optical response of the nanostructured arrays.

  • 140.
    Mendoza-Galvan, A.
    et al.
    CINVESTAV, Mexico.
    Munoz-Pineda, E.
    CINVESTAV, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Birefringence of nanocrystalline chitin films studied by Mueller-matrix spectroscopic ellipsometry2016In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 6, no 2, p. 671-681Article in journal (Refereed)
    Abstract [en]

    Birefringent chitin films were prepared by a dipping technique from aqueous suspensions of chitin nanocrystals in a nematic liquid crystal phase. In the films, chitin nanocrystals are preferentially oriented along the withdrawal direction. Normal incidence transmission Mueller-matrix (M) spectroscopic ellipsometry measurements as a function of sample rotation were used to investigate the optical birefringence in the spectral range 0.73 to 5 eV. Analysis of eigenvalues and depolarization data reveal that the Mueller matrix corresponds to a pure retarder for photon energies below 4 eV and is depolarizing in the range 4 to 5 eV. By modeling the chitin film as a slab with in-plane anisotropy the birefringence was determined. The determination of birefringence was extended to include the range of 4 to 5 eV by a differential decomposition of M. (C) 2016 Optical Society of America

  • 141.
    Mendoza-Galvan, Arturo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Huang, Yi-Fan
    National Taipei University of Technology.
    Chen, Li-Chyong
    National Taipei University of Technology.
    Chen, Kuei-Hsien
    National Taiwan University.
    Spectroscopic ellipsometry analysis of silicon nanotips obtained by electron cyclotron resonance plasma etching2009In: APPLIED OPTICS, ISSN 0003-6935, Vol. 48, no 26, p. 4996-5004Article in journal (Refereed)
    Abstract [en]

    Silicon nanotips fabricated by electron cyclotron resonance plasma etching of silicon wafers are studied by spectroscopic ellipsometry. The structure of the nanotips is composed of columns 100-140 nm wide and spaced by about 200 nm. Ellipsometry data covering a wide spectral range from the midinfrared to the visible are described by modeling the nanotip layer as a graded uniaxial film using the Bruggeman effective medium approximation. The ellipsometry data in the infrared range reveal two absorption bands at 754 and 955 cm(-1), which cannot be resolved with transmittance measurements. These bands indicate that the etching process is accompanied with formation of carbonaceous SiC and CHn species that largely modify the composition of the original crystalline silicon material affecting the optical response of the nanotips. (C) 2009 Optical Society of America

  • 142.
    Mendoza-Galvan, Arturo
    et al.
    Cinvestav-Querétaro, Libramiento Norponiente.
    Rybka, M
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Magnuson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Barsoum, Michel
    Drexel University.
    Spectroscopic ellipsometry study on the dielectric function of bulk Ti2AlN,Ti2AlC, Nb2AlC, (Ti0.5,Nb0.5)2AlC, and Ti3GeC2 MAX-phases2011In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, p. 013530-Article in journal (Refereed)
    Abstract [en]

    The averaged complex dielectric function =2+ /3 of polycrystalline Ti2AlN, Ti2AlC,Nb2AlC, Ti0.5,Nb0.52AlC, and Ti3GeC2 was determined by spectroscopic ellipsometry coveringthe mid infrared to the ultraviolet spectral range. The dielectric functions and correspond tothe perpendicular and parallel dielectric tensor components relative to the crystallographic c-axis ofthese hexagonal compounds. The optical response is represented by a dispersion model with Drude–Lorentz and critical point contributions. In the low energy range the electrical resistivity is obtainedfrom the Drude term and ranges from 0.48 m for Ti3GeC2 to 1.59 m for Ti0.5,Nb0.52AlC.Furthermore, several compositional dependent interband electronic transitions can be identified. Forthe most important ones, Im shows maxima at: 0.78, 1.23, 2.04, 2.48, and 3.78 eV for Ti2AlN;0.38, 1.8, 2.6, and 3.64 eV for Ti2AlC; 0.3, 0.92, and 2.8 eV in Nb2AlC; 0.45, 0.98, and 2.58 eV inTi0.5,Nb0.52AlC; and 0.8, 1.85, 2.25, and 3.02 eV in Ti3GeC2.

  • 143.
    Mendoza-Galvan, Arturo
    et al.
    Cinvestav-Queretaro, Mexico.
    Rybka, Marcin
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Magnuson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Barsoum, Michel
    Drexel University.
    Spectroscopic Ellipsometry of Bulk MAX-phases2009In: Proceedings of the AVS 56th International Symposium & Exhibition, 2009, 2009Conference paper (Other academic)
    Abstract [en]

    MAX-phases are compounds with the chemical formula Mn+1AXn where M is a transition metal, A is an element from column 13 to 16 in the periodic system and X represents C or N and n = 1, 2 or 3. These materials are potentially technologically important as they show unique refractory and other physical properties due to the combination of metals and ceramics. From a fundamental point of view the band structure of these materials are of interest and optical reference data are important to determine. Herein we report, for the first time, on the optical properties of NbTiAlC, Nb2AlC, TiSC2, Cr2GeC, TiGeC2, Ti2AlC, and Ti2AlN by spectroscopic ellipsometry in the 0.03 to 6.0 eV spectral range. The ellipsometric data in the infrared range show features corresponding to Fano modes indicating the presence of a thin oxide layer a few nm thick. The optical response of these MAX-phases is represented by a Drude-Lorentz model. Thus, in the low energy range the electrical conductivity through the Drude term is evaluated and two or three interband electronic transitions which are compositional dependent can be identified at photon energies in the visible-ultraviolet range 1.0-6.0 eV.

  • 144.
    Mendoza-Galván, Arturo
    et al.
    Cinvestav-Querétaro, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Huang, I.F.
    National Taipei University of Technology.
    Chen, K.H
    National Taiwan University.
    Spectroscopic ellipsometry analysis of silicon nanotips obtained by electron cyclotron resonance plasma etching2009Conference paper (Other academic)
  • 145.
    Mendoza-Galván, Arturo
    et al.
    Cinvestav-IPN, Unidad Querétaro, Querétaro, Mexico .
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Dmitriev, Alexander
    Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Pakizeh, T.
    Faculty of Electrical and Computer Engineering, K. N. Toosi University of Technology, Tehran, Iran.
    Käll, Mikael
    Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Fano interference in supported gold nanosandwiches with weakly coupled nanodisks2012In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 28, p. 29646-29658Article in journal (Refereed)
    Abstract [en]

    We studied the far-field optical response of supported gold-silica-gold nanosandwiches using spectroscopic ellipsometry, reflectance and transmittance measurements. Although transmittance data clearly shows that the gold nanodisks in the sandwich structure interact very weakly, oblique reflectance spectra of s- and p-polarized light show clearly asymmetric line-shapes of the Fano type. However, all experimental results are very well described by modeling the gold nanodisks as oblate spheroids and by employing a 2 × 2 scattering matrix formulation of the Fresnel coefficients provided by an island film theory. In particular, the Fano asymmetry can be explained in terms of interference between the scattered waves from the decoupled nanodisks in the spectral range limited by their respective plasmon resonances. We also show that the reflectance and ellipsometry spectra can be described by a three-layer system with uniaxial effective dielectric functions.

  • 146.
    Mendoza-Galván, Arturo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology.
    Muñoz-Pineda, Eloy
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Ribeiro, S.J.L.
    LaMF—UNESP Instituto de Química, Araraquara, Brazil.
    Vieira Dos Santos, M.
    LaMF—UNESP Instituto de Química, Araraquara, Brazil.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Mueller matrix spectroscopic ellipsometry study of nanocrystalline cellulose free-standing chiral films2015Conference paper (Other academic)
    Abstract [en]

    The astonishing colors exhibited by many birds, insects and other creatures have inspired the development of materials and structures for optical biomimetics. Particularly, aqueous suspensions of cellulose nanocrystals self-assembly in a chiral nematic liquid crystalline phase producing nanocrystalline cellulose (NCC) chiral films after slow evaporation [1] that mimic the left-handed helicoidal arrangement of chitin-protein fibrils found in some beetle cuticles. Owing to the helical structure, left-handed polarized light is selectively reflected from beetle cuticles and NCC chiral films at normal incidence in a spectral band centered at wavelength l0=nL where n is the in-plane average refractive index and L the helix pitch.

    In this work we report the normalized Mueller matrix (M) of NCC free-standing chiral films measured with a dual rotating compensator ellipsometer (J. A. Woollam Co., Inc.) in the wavelength (l) range  250-1000 nm. Measurements performed on NCC films in reflection at angles of incidence (q) between 20 and 75° are shown in the contour map in Fig. 1 and display the same structure as those found in M of beetle cuticles [2]. At q=20° the band of selective reflection of left-handed polarized light (m41=m14<0) is centered at 520 nm. However, NCC chiral films are characterized by a mosaic-like texture as can be observed in the optical microscopy image inserted on the right panel of Fig. 1. The multidomain texture indicates both random helix direction and pitch distribution. Therefore, measurements in different places show selective reflection bands with different spectral characteristics. On the other hand, the transmission of right-handed polarized light (m41=m14>0) is confirmed from measurements at normal incidence, as observed in the right panel of Fig. 1. Other properties of the transmitted light like degree of polarization, ellipticity, and azimuth are determined for incident unpolarized as well as for different polarizations of incident light. Also, circular dichroism and optical rotation of NCC chiral films are evaluated.

    References

    [1] J. A. Kelly et al, Acc. Chem. Res. 47 (2014) 1088−1096.

    [2] E. Muñoz-Pineda et al, Thin Solid Films (2014) http://dx.doi.org/10.1016/j.tsf.2013.11.144

  • 147.
    Muller, Christian
    et al.
    Esfera UAB.
    Bergqvist, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Vandewal, Koen
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Tvingstedt, Kristofer
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Anselmo, Ana Sofia
    Karlstads University.
    Magnusson, Roger
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Alonso, M .Isabel
    Esfera UAB.
    Moons, Ellen
    Karlstads University.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Campoy-Quiles, Mariano
    Esfera UAB.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Phase behaviour of liquid-crystalline polymer/fullerene organic photovoltaic blends: thermal stability and miscibility2011In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, no 29, p. 10676-10684Article in journal (Refereed)
    Abstract [en]

    The thermal behaviour of an organic photovoltaic (OPV) binary system comprised of a liquid-crystalline fluorene-based polymer and a fullerene derivative is investigated. We employ variable-temperature ellipsometry complemented by photo-and electroluminescence spectroscopy as well as optical microscopy and scanning force nanoscopy to explore phase transitions of blend thin films. The high glass transition temperature correlates with the good thermal stability of solar cells based on these materials. Furthermore, we observe partial miscibility of the donor and acceptor together with the tendency of excess fullerene derivative to segregate into exceedingly large domains. Thus, for charge generation less adequate bulk-heterojunction nanostructures are poised to develop if this mixture is exposed to more elevated temperatures. Gratifyingly, the solubility of the fullerene derivative in the polymer phase is found to decrease if a higher molecular-weight polymer fraction is employed, which offers routes towards improving the photovoltaic performance of non-crystalline OPV blends.

  • 148.
    Muñoz-Pineda, Eloy Guadalupe
    et al.
    Cinvestav-Unidad Queretaro, Mexico.
    Mendoza-Galván, Arturo
    Cinvestav-Queretaro, Mexico.
    Mauricio-Sánchez, Reina Araceli
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Polarization properties and structural color of the scarab beetle Cotinis mutabilis (Mayatl)2012Conference paper (Other academic)
    Abstract [en]

    Nature offers a plethora of possibilities for optical biomimetics. Some birds, butterflies, insects and other creatures exhibit brilliant colors as result of diverse optical phenomena produced by micro- and nanostructures at the near surface. Particularly, the shiny metallic colors reflected by the exoskeleton (the so called cuticle) of some beetles show elliptical polarization properties; most commonly of the left-handed type but also the right-handed type has been found [1]. These color and polarization properties have been related to a twisted plywood or Bouligand structure which is comprised by the clustering of chitin nanofibrils wrapped by proteins in a planar woven.

    In this work we report the polarization properties of light reflected from the scarab beetle Cotinis mutabilis (Gory and Percheron 1833) and the microstructure of its cuticle. This species is found in Mexico and the southwestern part of the United States. The specimen under study was collected at the facilities of Cinvestav in Querétaro, Mexico where it is known as mayate (Mayatl in Náuhtl, the language of Aztecs). The Mayatl presents a green mate color in its dorsal side with red-orange stripes in the elytra. On the other hand, the abdominal side shows a shiny green metallic color which is subject of the present study. The polarization properties are investigated by the complete Mueller matrix (M) measured with a dual rotating compensator ellipsometer (J. A. Woollam Co., Inc.) at angles of incidence of 20-75° and wavelength range of 250-1000 nm. In particular, the elements m41 and m14 of M show that green left-handed polarized light is reflected when the beetle is illuminated at near-normal angles of incidence with unpolarized white light. As the angle of incidence increases the maximum of light reflected is blue-shifted. The degree of polarization, ellipticity, and azimuth calculated with relationships between mj1 elements provide a full description of the polarization state of light reflected from the beetle’s cuticle for incident un-polarized light. Scanning electron microscopy images of the cuticle reveal that the epicuticle and exocuticle comprise a (hard) layer ca. 15 μm thick. Two regions can be differentiated in the exocuticle: the outer exocuticle without any clear structure and the inner exocuticle where a clear multilayer structure is observed. Beneath the inner exocuticle is the endocuticle which is comprised by unidirectional layers of microfibrils alternate with layers running at nearly right angles to each other in a pseudo-orthogonal arrangement. The cuticle also was imaged with a microscope coupled to a FTIR system allowing further identification of bands due to chitin.

  • 149.
    Muñoz-Pineda, Eloy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology. Cinvestav-IPN, Unidad Querétaro, Libramiento Norponiente 2000, Querétaro, Mexico.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Arwin, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Mendoza-Galván, Arturo
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology. Cinvestav-IPN, Unidad Querétaro, Libramiento Norponiente 2000, Querétaro, Mexico.
    Symmetries and relationships between elements of the Mueller matrix spectra of the cuticle of the beetle Cotinis mutabilis2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 571, p. 660-665Article in journal (Refereed)
    Abstract [en]

    The optical properties of light reflected from the cuticle of the scarab beetle Cotinis mutabilis are studied using variable angle Mueller matrix spectroscopic ellipsometry. Reflection of left-handed polarized light is demonstrated. Large amplitude interference oscillations in the elements of the normalized Mueller matrix (M) reveal highly transparent materials comprising the beetle cuticle. Off-diagonal elements in M obey simple symmetry relationships due to the constraint in the cross-polarized reflection coefficients between p and s polarizations of chiral systems, rps = − rsp. Based on the latter constraint and further interrelationships experimentally investigated, the number of independent elements in M resulted in only six. Reciprocity is probed from measurements performed in opposite sample orientations and the effects on M due to sample rotation by 90° are discussed. The results suggest relatively large areas in the cuticle of C. mutabilis with a helicoidal structure comprised of fibrils with a well-defined orientation.

  • 150.
    Nilsson, Christina
    et al.
    Department of Sensor Technology, Swedish Defense Research Agency, FOI Linköping University, IFM, Tillämpad optik.
    Jänis, A.
    Department of Sensor Technology Swedish Defense Research Agency, FOI.
    Kariis, Hans
    Department of Sensor Technology Swedish Defense Research Agency, FOI.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Järrendahl, Kenneth
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Combining Spectroscopic Ellipsometry and Vector Network Analysis to obtain Electromagnetic Response in a Wide Wavelength Region2007In: 4th International Conference on Spectroscopic Ellipsometry,2007, Linköping: Linköpings universitet , 2007, p. 136-Conference paper (Refereed)
12345 101 - 150 of 217
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