| 1. |
- Arwin, Hans
(author)
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Ellipsometry on thin organic layers of biological interest : Characterization and applications
- 2000
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In: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 377-378, s. 48-56
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Journal article (peer-reviewed)abstract
- The thickness resolution and in situ advantage of ellipsometry make this optical technique particularly suitable for studies of thin organic layers of biological interest. Early ellipsometric studies in this area mainly provided thickness quantification, often expressed in terms of surface mass. However, today it is possible to perform monolayer spectroscopy, e.g. of a protein layer at a solid/liquid interface, and also to resolve details in the kinetics of layer formation. Furthermore, complicated microstructures, like porous silicon layers, can be modeled and protein adsorption can be monitored in such layers providing information about pore filling and penetration depths of protein molecules of different size and type. Quantification of adsorption and microstructural parameters of thin organic layers on planar surfaces and in porous layers is of high interest, especially in areas like biomaterials and surface-based biointeraction. Furthermore, by combining ellipsometric readout and biospecificity, possibilities to develop biosensor concepts are emerging. In this report we review the use of ellipsometry in various forms for studies of organic layers with special emphasis on biologically-related issues including in situ monitoring of protein adsorption on planar surfaces and in porous layers, protein monolayer spectroscopy and ellipsometric imaging for determination of thickness distributions. Included is also a discussion about recent developments of biosensor systems and possibilities for in situ monitoring of engineering of multilayer systems based on macromolecules.
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| 2. |
- Rantzer, Annika, 1971-, et al.
(author)
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Optical properties of intrinsic and doped a-Si:H films grown by d.c. magnetron sputter deposition
- 2001
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In: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 394:1-2, s. 255-262
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Journal article (peer-reviewed)abstract
- Thin films of intrinsic, B- and P-doped a-Si:H were grown by d.c. magnetron sputter deposition. The doping was accomplished by doped targets and co-sputtering Si and B4C. Spectroscopic ellipsometry was used for optical characterization and multiple sample analysis was applied to extract the dielectric functions of intrinsic films with 8–10 at.% hydrogen content, boron doped films with 2.2 at.% hydrogen and phosphorous-doped films with hydrogen contents of 10–15 at.%. One of the phosphorous-doped films was micro-crystalline. Hydrogen content was determined by nuclear reaction analysis. From the obtained optical properties the absorption and the optical gap were studied addressing p–i–n diode applications. The optical gaps for intrinsic a-Si:H material were 1.88±0.03 eV as determined by Tauc analysis and 1.45±0.06 eV by applying Cody analysis.
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| 3. |
- Arwin, Hans, 1950-, et al.
(author)
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Comparison and analysis of Mueller-matrix spectra from exoskeletons of blue, green and red Cetonia aurata
- 2014
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In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 571, s. 739-743
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Journal article (peer-reviewed)abstract
- The exoskeleton, also called the cuticle, of specimens of the scarab beetle Cetonia aurata is a narrow-band reflector which exhibits metallic shine. Most specimens of C. aurata have a reflectance maximum in the green part of the spectrum but variations from blue–green to red–green are also found. A few specimens are also more distinct blue or red. Furthermore, the reflected light is highly polarized and at near-normal incidence near-circular left-handed polarization is observed. The polarization and color phenomena are caused by a nanostructure in the cuticle. This nanostructure can be modeled as a multilayered twisted biaxial layer from which reflection properties can be calculated. Specifically we calculate the cuticle Mueller matrix which then is fitted to Mueller matrices determined by dual-rotating compensator ellipsometry in the spectral range 400–800 nm at multiple angles of incidence. This non-linear regression analysis provides structural parameters like pitch of the chiral structure as well as layer refractive index data for the different layers in the cuticle. The objective here is to compare spectra measured on C. aurata with different colors and develop a generic structural model. Generally the degree of polarization is large in the spectral region corresponding to the color of the cuticle which for the blue specimen is 400–600 nm whereas for the red specimen it is 530–730 nm. In these spectral ranges, the Mueller-matrix element m41 is non-zero and negative, in particular for small angles of incidence, implicating that the reflected light becomes near-circularly polarizedwith an ellipticity angle in the range 20°–45°.
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| 4. |
- Berlind, Torun, 1965-, et al.
(author)
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Spectroscopic ellipsometry characterization of amorphous carbon and amorphous,graphitic and fullerene-like carbon nitride thin films
- 2009
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In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 517:24, s. 6652-6658
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Journal article (peer-reviewed)abstract
- Carbon nitride (CNx) and amorphous carbon (a-C) thin films are deposited by reactive magnetron sputtering onto silicon (001) wafers under controlled conditions to achieve amorphous, graphitic and fullerene-like microstructures. As-deposited films are analyzed by Spectroscopic Ellipsometry in the UV–VIS–NIR and IR spectral ranges in order to get further insight into the bonding structure of the material. Additional characterization is performed by High Resolution Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Between eight and eleven resonances are observed and modeled in the ellipsometrically determined optical spectra of the films. The largest or the second largest resonance for all films is a feature associated with C–N or C–C modes. This feature is generally associated with sp3 C–N or sp3 C–C bonds, which for the nitrogen-containing films instead should be identified as a three-fold or two-fold sp2 hybridization of N, either substituted in a graphite site or in a pyridine-like configuration, respectively. The π→πlow asterisk electronic transition associated with sp2 C bonds in carbon films and with sp2 N bonds (as N bonded in pyridine-like manner) in CNx films is also present, but not as strong. Another feature present in all CNx films is a resonance associated with nitrile often observed in carbon nitrides. Additional resonances are identified and discussed and moreover, several new, unidentified resonances are observed in the ellipsometric spectra.
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| 5. |
- Fernandez Del Rio, Lía, 1985-, et al.
(author)
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Polarizing properties and structural characteristics of the cuticle of the scarab Beetle Chrysina gloriosa
- 2014
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In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 571:3, s. 410-415
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Journal article (peer-reviewed)abstract
- The scarab beetle Chrysina gloriosa is green with gold-colored stripes along its elytras. The properties of light reflected on these areas are investigated using Mueller-matrix spectroscopic ellipsometry. Both areas reflect light with high degree of left-handed polarization but this effect occurs for specular reflection for the gold-colored areas and for off-specular angles for the green areas. The colors and polarization phenomena originate from reflection of light in the cuticle and a structural analysis is presented to facilitate understanding of the different behaviors of these two areas. Scanning electron microscopy (SEM) images of the cross section of beetle cuticles show a multilayered structure. On the gold-colored areas the layers are parallel to the surface whereas on the green-colored areas they form cusp-like structures. Optical microscopy images show a rather flat surface in the gold-colored areas compared to the green-colored areas which display a net of polygonal cells with star-shaped cavities in the center. Each of the polygons corresponds to one of the cusps observed in the SEM images. Atomic force microscopy images of the star-shaped cavities are also provided. The roughness of the surface and the cusp-like structure of the green-colored areas are considered to cause scattering on this area.
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| 6. |
- Lunca Popa, Petru, et al.
(author)
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Structural, morphological, and optical properties of Bi2O3 thin films grown by reactive sputtering
- 2017
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In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 624, s. 41-48
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Journal article (peer-reviewed)abstract
- Bi2O3 thin films were grown using reactive RF sputtering from a metallic Bi target. The influence of various deposition parameters (substrate temperature, applied power on target and oxygen content in the working gas) on the morphology, structure and optical properties of films was investigated. Depending on the O-2/(Ar + O-2) ratio of the working gas, bismuth, delta-Bi2O3, alpha-Bi2O3 or a mixture of these phases can be deposited, with a narrow window for growth of [111]-oriented delta-Bi2O3 thin films. The delta-Bi2O3 phase is stable from room temperature up to 350 degrees C (in air), where an irreversible transition to alpha-Bi2O3 occurs. This phase transformation is also shown to occur during TEM sample preparation, because of the inherent heating from the ion-milling process, unless liquid -nitrogen cooling is used. (C) 2017 Published by Elsevier B.V.
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| 7. |
- Magnusson, Roger, et al.
(author)
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Optical Mueller Matrix Modeling of Chiral AlxIn1-xN Nanospirals
- 2014
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In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 571, s. 447-452
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Journal article (peer-reviewed)abstract
- 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.
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| 8. |
- Muñoz-Pineda, Eloy, et al.
(author)
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Symmetries and relationships between elements of the Mueller matrix spectra of the cuticle of the beetle Cotinis mutabilis
- 2014
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In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 571, s. 660-665
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Journal article (peer-reviewed)abstract
- 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.
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| 9. |
- Nygren, Kristian, et al.
(author)
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Optical methods to quantify amorphous carbon in carbide-based nanocomposite coatings
- 2017
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In: Thin Solid Films. - : ELSEVIER SCIENCE SA. - 0040-6090 .- 1879-2731. ; 638, s. 291-297
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Journal article (peer-reviewed)abstract
- We report how the total carbon content and the amorphous carbon (a-C) phase fraction in transition metal carbide/a-C nanocomposite coatings can be obtained using optical methods, which are much more practical for industrial use than conventional X-ray photoelectron spectroscopy. A large set of carbon-containing nanocomposite coatings deposited using different magnetron sputtering techniques were analyzed by X-ray photoelectron spectroscopy, reflectance spectrophotometry, and spectroscopic ellipsometry. The chemical composition and the a-C phase fraction were determined by X-ray photoelectron spectroscopy for each coating and results are presented for the Ti-C, Cr-C, and Nb-C systems. The composition and the a-C phase fraction are correlated to optical reflectance in the visible range, by parametrization in L*a*b* color space, and by ellipsometry primary data. Results show that it is possible to rapidly estimate the composition and the a-C fraction using these optical methods. We propose that optical methods have promising use in the industry as a cost-efficient technique for characterization of carbide-based coatings. (C) 2017 Elsevier B.V. All rights reserved.
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| 10. |
- Poksinski, Michal, 1976-, et al.
(author)
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Protein monolayers monitored by internal reflection ellipsometry
- 2004
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In: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 455-456, s. 716-721
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Journal article (peer-reviewed)abstract
- Total internal reflection ellipsometry (TIRE) in spectroscopic mode in the wavelength range 400–1200 nm is employed in situ at a solid/liquid interface for investigation of protein adsorption on thin semitransparent gold films. In this configuration, the surface plasmon resonance phenomenon gives a large enhancement of the thin film sensitivity. Adsorption of a monolayer of the protein ferritin is monitored kinetically in situ and results in a change in the ellipsometric parameter Δ of more than 90° compared to 3° in similar ellipsometric measurements on gold substrates. This large sensitivity demonstrates a potential for sensor applications. The ferritin layer optical function is modeled with a Cauchy dispersion model resulting in a layer thickness of 9.2 nm, in good agreement with the dimension of the ferritin molecules. A transition layer between the protein film and the gold layer is necessary to introduce in the model to account for interactions between the protein layer and the gold film. The large sensitivity of TIRE for thin layers opens up a pathway to analyze in detail the structure of thin protein layers provided that a further development of the experimental setup and the model for the protein layer is carried out.
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