Search results for "ellipsometry"
showing 10 items of 49 documents
Pulmonary surfactant protein C containing lipid films at the air-water interface as a model for the surface of lung alveoli.
1995
The pulmonary surfactant lines as a complex monolayer of lipids and proteins the alveolar epithelial surface. The monolayer dynamically adapts the surface tension of this interface to the varying surface areas during inhalation and exhalation. Its presence in the alveoli is thus a prerequisite for a proper lung function. The lipid moiety represents about 90% of the surfactant and contains mainly dipalmitoylphosphatidylcholine (DPPC) and phosphatidylglycerol (PG). The surfactant proteins involved in the surface tension adaption are called SP-A, SP-B and SP-C. The aim of the present investigation is to analyse the properties of monolayer films made from pure SP-C and from mixtures of DPPC, DP…
Formation and Characterization of Self-Assembled Films of Thiol-Derivatized Poly(Dimethylsiloxane) on Gold
1997
Poly(dimethylsiloxane) (PDMS) copolymers containing propanethiol side chain “stickers” for forming self-assembled films on gold surfaces have been studied by various experimental techniques including ellipsometry, contact angle measurements, FT-IR, angle-dependent XPS, and ToF−SIMS. The results show that the thiol-containing side chains do not all chemisorb to the gold surfaces. In addition, the concentration of these sticker units was found to have a dominant effect on the polymer film thickness, the surface wetting properties, and the orientation of the PDMS backbone. Ab initio calculations reveal that the IR-active PDMS Si−O stretching bands can be used as indications of chain orientatio…
Tuning Optical Properties of Al 2 O 3 /ZnO Nanolaminates Synthesized by Atomic Layer Deposition
2014
Nanolaminates are of great interest for their unique properties such as high dielectric constants and advanced mechanical, electrical, and optical properties. Here we report on the tuning of optical and structural properties of Al2O3/ZnO nanolaminates designed by atomic layer deposition (ALD). Structural properties of nanolaminates were studied by SEM, GIXRD, and AFM. Optical characterization was performed by transmittance and photoluminescence (PL) spectroscopy. Complex study of monolayer properties was performed by ellipsometry. Optical constants for Al2O3 and ZnO monolayer were calculated. The band gap of ZnO single layers and the excitonic PL peak position were shifted to the UV region …
Wood fiber orientation assessment based on punctual laser beam excitation: A preliminary study
2016
International audience; The EU imposes standards for the use of wood in structural applications. Local singularities such as knots affect the wood mechanical properties. They can be revealed by looking at the wood fiber orientation. For this reason, many methods were proposed to estimate the orientation of wood fiber using optical means, X-rays, or scattering measurement techniques. In this paper, an approach to assess the wood fiber orientation based on thermal ellipsometry is developed. The wood part is punctually heated with a Nd-YAG Laser and the thermal response is acquired by an infrared camera. The thermal response is elliptical due to the propagation of the heat through and along th…
Melting and interdigitation of microstructured solid supported membranes quantified by imaging ellipsometry
2010
The phase transition of individually addressable microstructured lipid bilayers was investigated by means of noncontact imaging ellipsometry. Two-dimensional membrane compartments were created on silicon substrates by micromolding in capillaries and the phase transition of supported dimyristoylphosphadiylcholine DMPC and dipentadecoylphosphatidylcholine DiC15PC membranes was determined measuring area expansion and thickness of the bilayer as a function of temperature, ethanol concentration, and cholesterol content. Apart from measuring the thermotropic behavior of DMPC on glass slides and silicon wafers, the authors were able to visualize the reversible induction of an interdigitated phase …
Above-bandgap ordinary optical properties of GaSe single crystal
2009
We report above-bandgap ordinary optical properties of ε-phase GaSe single crystal. Reference-quality pseudodielectric function 〈ε(E)〉 = 〈ε1(E)〉+i〈ε2(E)〉 and pseudorefractive index 〈N(E)〉 = 〈n(E)〉+i〈k(E)〉 spectra were measured by spectroscopic ellipsometry from 0.73 to 6.45 eV at room temperature for the light polarization perpendicular to the optic axis (math⊥math). The 〈ε〉 spectrum exhibited several interband-transition critical-point structures. Analysis of second-energy derivatives calculated numerically from the measured data yielded the critical-point energy values. Carmen.Martinez-Tomas@uv.es
Ellipsometric study of the physical states of phosphatidylcholines at the air-water interface
1990
Etude des couches monomoleculaires de dimyristoylphosphatidylcholine, de dipalmitoylphosphatidylcholine, de distearoyl phosphatidylcholine, de diarachidoylphosphatidylcholine a l'interface air/eau
Morphological and chemical dynamics upon electrochemical cyclic sodiation of electrochromic tungsten oxide coatings extracted by in situ ellipsometry.
2020
The sodiation–desodiation process of sputtered amorphous electrochromic tungsten oxide coatings in an aqueous-based medium was simultaneously monitored over 99 cycles by cyclic voltammetry and in situ spectroscopic ellipsometry. This allowed extracting the evolution of optical and geometrical parameters upon cycling. The resulting electrochemical coloring-bleaching process was dynamically fitted in the 1.8–2.8 eV optical range with a four-phase model including a constrained spline parametrization of the dielectric function. This allows real time access to thickness, surface roughness, and dielectric function of N a x W O 3 . The temporal evolution of the latter in the fully colored state wa…
Band gap of corundumlike α−Ga2O3 determined by absorption and ellipsometry
2017
The electronic structure near the band gap of the corundumlike $\ensuremath{\alpha}$ phase of ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ has been investigated by means of optical absorption and spectroscopic ellipsometry measurements in the ultraviolet (UV) range (400--190 nm). The absorption coefficient in the UV region and the imaginary part of the dielectric function exhibit two prominent absorption thresholds with wide but well-defined structures at 5.6 and 6.3 eV which have been ascribed to allowed direct transitions from crystal-field split valence bands to the conduction band. Excitonic effects with large Gaussian broadening are taken into account through the Elliott-Toyozawa model, which y…
Formation of Optical Gradient in Chemical Solution-Derived PbZr[sub 0.52]Ti[sub 0.48]O[sub 3] Thin Films: Spectroscopic Ellipsometry Investigation
2009
Investigation using a variable angle spectroscopic ellipsometer revealed the influence of sample preparation conditions on sol-gel PbZr 0.52 Ti 0.48 O 3 (PZT 52/48) thin-film homogeneity that allows identification and further optimization of thin-film performance. Separate crystallization of the layers determined the optical gradient appearance, irrespective of the chemical solvents used in this work. A more refined analysis showed that a refractive index gradient was apparent in the samples in which lattice parameters strongly changed with thickness. For these films, energy-dispersive X-ray spectroscopy analysis showed significant variation in Pb and Zr. Additionally, complex dielectric fu…