A computationally efficient algorithm based on the reduced Rayleigh equation, combined with an optimization scheme, is used to accurately retrieve the morphological parameters of a two-dimensional plasmonic photonic crystal from angle-resolved spectroscopic Mueller matrix ellipsometric measurements. The numerical method is successfully tested against experimental data and gives morphological parameters consistent with SEM and AFM measurements.

Hyperbolic metamaterials use the concept of controlling the propagative modes through the engineering of the dispersion relation, and are considered highly promising to reach different meta-properties. Spectroscopic Mueller Matrix Ellipsometry with variable angle of incidence and full azimuthal rotation of the sample is a powerful optical technique to characterize both anisotropic and bi-anisotropic materials. We here discuss the experimentally extracted uniaxial and biaxial optical properties of two self-assembled plasmonic systems that appear to have the appropriate meta-dispersion relations. The metasurface was produced by oblique incidence angle ion beam sputtering of glass followed by shadow deposition of Au [1]. The second bulk metamaterial was a block-copolymer based self-assembled hyperbolic metamaterial of nanocomposites based on metal nanoparticles embedded in a self-assembled anisotropic polymer host, presenting a strong spectrally selective optical anisotropy [2]. The extracted effective dielectric functions and the resulting dispersion relations are presented.

A gold nanowired grid polarizer is studied in the mid-IR range by means of spectroscopic Mueller matrix ellipsometry. This material is also an example of a so-called 2-dimensional hyperbolic metamaterial/metasurface, and produced by low-cost large area scalable manufacturing techniques. We present the IR spectroscopic Mueller matrix optical response of such sample for a full azimuthal rotation. It is observed strong in-plane anisotropy due to the gold wire grid. The main objective is to show a characterization methodology to reveal the complete polarimetric response over a large spectral range, providing information about the effective optical properties of the sample. Three different optical models are proposed that catch the main features of experimental data. The first one is based on the Rigorous Coupled-Wave Analysis (RCWA) assuming the profile of the sample to be periodic, second, a Generalized Effective Medium Approximation (G-EMA) assuming oriented gold ellipsoids aligned along the lines of the wire grid, and third, a biaxial dispersion model. Experimental data is compared with simulated data obtained from the three optical models and a comparative analysis between them is presented. The different models allow to retrieve information on the characteristic dimensions of the nanowires, and also to obtain the two in-plane components of the effective dielectric tensor of the nanostructured layer. The tensor component parallel to the nanowires shows a metallic response whereas the component perpendicular to them behaves as a transparent dielectric. Moreover, we have also shown that the nanowired grid behaves as a hyperbolic material. (C) 2016 Elsevier B.V. All rights reserved.

An original method for surface modification of metal nanoparticles and insertion in sol–gel monoliths is reported. The optical characterizations show the particle self-orientation in the bulk.

We demonstrate that small tilts away from the substrate normal, of short (30–40nm high) nanopillars, may be detected and modeled by spectroscopic UV–Visible Mueller Matrix Ellipsometry (MME). The pillars were produced by sputtering a GaSb substrate with a low energy unfocused ion beam. It has previously been found that the pillars will point in the direction of the ion flux. For both samples reported here, the ion-incidence was unintentionally tilted away from the substrate normal by 2.8 and 4.8°. The MME measurements were performed using both multiple angles of incidence, and 360° rotation of the incidence plane. Graded uniaxial effective medium models were fitted to the experimental data, and through Euler angle rotations of the dielectric tensor, the tilt angle and the orientation of the pillar direction, were obtained. The UV part of the spectrum enhanced the tilt angle sensitivity down to 0.02–0.05°. A data presentation that enhances the understanding of the symmetry in the crystallographic information obtained from spectroscopic MME is proposed. The off block diagonal Mueller matrix elements are more sensitive to the in-plane anisotropy, whereas for small tilt angles m14 scales approximately with θsin(ϕ).

Broadened plasmon resonances of Cu nanoparticles in nanopatterned mixed oxide sol-gel nanopillars are shown to be readily detected by spectroscopic Mueller matrix ellipsometry. The plasmonic nanomaterials are obtained by low energy ion sputtering of a CuO sol-gel film. Both s- and p-polarized plasmon resonances are observed in the off-block-diagonal and the block-diagonal Mueller matrix elements as well as in the generalized ellipsometric parameters. The resonant features in all elements correlate with both maximum depolarization and a minimum in the reflected intensity. The spectral position and the polarization character of the plasmon resonances are discussed phenomenologically through effective medium theory.

Color in living organisms is primarily generated by two mechanisms: selective absorption by pigments and structural coloration, or a combination of both. In this study, we investigated the coloration of cuticle from the wings (elytra) of the two ground beetle species Carabus auronitens and Carabus auratus. The greenish iridescent color of both species is created by a multilayer structure consisting of periodically alternating layers with different thicknesses and composition which is located in the 1-2 µm thick outermost layer of the cuticle (epicuticle). Illuminated with white light, reflectance spectra in both linear polarisation show an angle-dependent characteristic peak in the blue/green region of the spectrum. Furthermore, the reflected light is polarised linearly. Scattering experiments with laser illumination at 532 nm show diffuse scattering over a larger angular range. The polarisation dependence of the scattered light is consistent with the interpretation of small inhomogeneities as scattering centres in the elytra.

The science and optical engineering of imaging Mueller Matrix Ellipsometry (MME) and Spectroscopic MME is currently being revitalized based on an efficient optimal design method, and through the use of the so-called Eig envalue Calibration Technique (ECT). Through the ECT one may efficiently measure the details of the polarization state generator (PSG) matrix, and the polarization state analyzer (PSA) matrix, and hence avoid modeling of any unknown polarizing components in the system, and in particular the exact response of complex polarizing elements such as liquid crystal retarders. We here start up with presenting a detailed an alysis of the dynamic response of a near infrared Ferroelectric Liquid Crystal based Mueller matrix ellipsometer (NIR FLC- MME) [1] . A time dependent simulation model, using the measured time response of the individual FLCs, is used to describe the measured temporal response. Furthermore, the impulse response of the detector and the pre-amplifier is characterized and in cluded in the simulation model. The measured time dependent intensity response of the MME is well explained by simulations. A FLC based NIRMME system is here shown to be able to operate accurately at the maximum speed of approximately 16 ms per Mueller matrix measurement (steady state response). We demonstrate here time dependent Mueller Matrix measurements of a dynamically changing sample, with even down to 8 ms sampling time of each complete Mueller Matrix (with some loss of accuracy). We secondly briefly present the NIR-FLC- MME imaging system, and show applications to strain imaging of a crystal subjected to an external pressure. Furthermore, we present near-infra-red Mueller matrix images and corresponding polar decomposition images of thin slices of bio-tissue [2].

We construct a simple phenomenological diffuse-interface model for composition-induced nanopatterning during ion sputtering of alloys. In simulations, this model reproduces without difficulties the high-aspect-ratio structures and tilted pillars observed in experiments. We investigate the time evolution of the pillar height, both by simulations and by in situ ellipsometry. The analysis of the simulation results yields a good understanding of the transitions between different growth regimes and supports the role of segregation in the pattern-formation process.

Inclined GaSb nanopillars prepared by low energy ion sputtering with oblique ion beam incidence have been characterized by two different Mueller matrix ellipsometric tools. The optical properties of the nanopillars were found to be well described by a uniaxial anisotropic graded effective medium model. The pillar height and inclination angle were determined by fitting the parameters of the effective medium model to spectroscopic (1.44–2.88 eV) Mueller matrix measurements at multiple azimuth sample orientations. A set of different samples with various average pillar height and inclination angle was studied; results from the optical characterization correspond well with those from scanning electron microscopy analysis. For samples with nanopillars inclined by 45° or less, the height could be determined from a single Mueller matrix measurement at only one azimuth orientation, allowing real-time in situ observation of the formation. The nanopillars were also studied using a single wavelength angle resolved Mueller polarimeter, which also can be used to determine height and inclination of the pillars, in addition to validating the optical model over a wide range of incident and azimuth angles.

We demonstrate that real-time in situ spectroscopic ellipsometry can be used to measure the height evolution of nanostructures during low energy ion sputtering of GaSb. A graded anisotropic effective medium approximation is used to extract the height from the optical measurements. Two different growth regimes have been observed, first exponential then followed by a linear regime. The linear regime is not expected from the traditional sputtering theories. The in situ results correspond well to ex situ atomic force microscopy measurements.

Nanostructured GaSb surfaces are investigated and characterised by Spectroscopic Ellipsometry (SE). In particular, the parameters of a recently developed graded anisotropic effective medium model are tentatively fitted to the data recorded from surfaces of densely packed long cones (higher than 60nm). Both single graded and double graded, anisotropic effective medium models are tested. In particular, we discuss the results from modelling the cones sputtered at normal incidence, with heights ranging from 80 to 230nm as determined by e.g. AFM and SEM.

High resolution field emission experiments from nanopatterned GaSb surfaces consisting of densely packed nanocones prepared by low ion-beam-energy sputtering are presented. Both uncovered and metal-covered nanopatterned surfaces were studied. Surprisingly, the field emission takes place by regular steps in the field emitted current. Depending on the field, the steps are either regular, flat, plateaus, or saw-tooth shaped. To the author's knowledge, this is the first time that such results have been reported. Each discrete jump in the field emission may be understood in terms of resonant tunneling through an extended surface space charge region in an n-type, high aspect ratio, single GaSb nanocone. The staircase shape may be understood from the spatial distribution of the aspect ratio of the cones.

Mueller matrix ellipsometers (MMEs) are known to be less affected by noise if the compensators have a 132 degrees phase shift between the slow and fast axis. This paper reports on the design and characterization of two custom-made achromatic compensators with minimal deviation from 132 degrees retardation as a function of wavelength. The compensators are based on the dual Fresnel rhomb geometry. One pair was made of CaF2 and the other of fused silica. These materials were selected due to their extended transparency range and optical quality. The CaF2 compensators were experimentally characterized in the 450-8000 nm range, whereas the less IR-transparent fused silica prisms were characterized between 450 and 1900 nm. Both kinds of retarders possessed the necessary properties needed for a broad-band achromatic Mueller matrix ellipsometer, since they were both shown to give well-conditioned system matrices within the measured wavelength regions. Specifically, the condition number for the dual prisms used as a Polarization State Generator (PSG) or Analyzer (PSA) was determined to be in the range 1.73-1.96, close to the optimal 3(1/2) value. Simulations of the optimal retarder configuration in terms of incidence angles and rotation angles are presented and discussed. From literature values of the optical constants it is shown that the compensators perform well at ultraviolet wavelengths down to approximately 150 nm.

This paper reports on the application of the first near-infrared spectroscopic Mueller Matrix Ellipsometer (MME) based on Ferro-electric Liquid Crystal retarders (FLC) and fixed waveplates. Operation of the instrument is demonstrated by transmission Mueller matrix measurements, and product decomposition of an imperfect dichroic polarizer and a depolarizing rough glass surface. The decomposition of the measured matrices is qualtitatively discussed in terms of retardance, diattenuation, depolarization, and azimuthal orientation.

Low energy ion-beam sputtering of GaSb results in self-organized nanostructures with the potential of structuring large surface areas. Characterization of such nanostructures by optical methods is studied and compared to direct (local) microscopic methods. The samples consist of densely packed GaSb cones on bulk GaSb, approximately 30, 50, and 300 nm in height, prepared by sputtering at normal incidence. The optical properties are studied by spectroscopic ellipsometry, in the range 0.6-6.5 eV, and with Mueller matrix ellipsometry in the visible range, 1.46-2.88 eV. The optical measurements are compared to direct topography measurements obtained by scanning electron microscopy, high resolution transmission electron microscopy, and atomic force microscopy. Good agreement is achieved between the two classes of methods when the experimental optical response of the short cones (<55 nm) is inverted with respect to topological surface information, via a graded anisotropic effective medium model. The main topological parameter measured was the average cone height. Optical methods are shown to represent a valuable characterization tool of nanostructured surfaces, in particular when a large coverage area is desirable. Because of the fast and nondestructive properties of optical techniques, they may readily be adapted to in situ configurations.

Optical measurements of nanostructured GaSb prepared by sputtering is presented. The optical response is studied by Mueller Matrix Ellipsometry (MME) in the visible range (430--850nm), and by spectroscopic ellipsometry in the range 0.6--6.5eV. The nano-structured surfaces reported in this work, consist of densely packed GaSb cones approximately 50nm high, on bulk GaSb. The nanostructured surfaces are here shown to considerably modify the optical response of the surface, hence giving a strong sensitivity to the far field spectroscopic (Mueller matrix) ellipsometric measurements. The off-specular scattering and the depolarization is found to be low. The anisotropic response is particularly emphasized by studying nano-structured GaSb cones approximately 45 degrees tilted with respect to the surface normal. In the latter case, one observes upon rotating the sample around the surface normal, that the Mueller matrix elements $m_{13}$ and $m_{14}$ oscillate as a function of the rotation angle. Finally, Mueller matrix techniques have been applied to the measured data, in order to analyze the acquired Mueller matrix in terms of physical realizability and noise.

This paper reports on the design and construction of the first near-infra-red spectroscopic Mueller Matrix Ellipsometer (MME) `based on Ferroelectric Liquid Crystal retarders (FLC) and fixed waveplates. The design was performed by assuming ideal optical polarizing components. In particular, the current FLC-MME is optimised to operate in the near-infra-red (NIR) spectral range from 800 nm to 1800 nm. The FLC based Polarization State Generator (PSG) and Polarization State Analyzer (PSA) have been optimized by keeping the condition number of the PSG's modulation matrix and the PSA's analysis matrix close to an optimum over the spectral design range, The design is realized in a setup using the full Mueller matrix measurement formalism based on the Eigenvalue Calibration Method (ECM). The actual modulation matrix and analysis matrix are obtained from the ECM, and the condition numbers immediately indicates the quality of the design.

Vapour deposition of Ce onto a Rh(1 1 0) single crystal at room temperature is studied by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and low energy electron diffraction (LEED). The thicknesses of the deposited Cc layers are estimated to be between 2 and 9 A. To study the changes in the Ce-Rh surface layer, the samples are annealed at temperatures between 500 and 1000 degrees C after Ce deposition.After heating, a c(2 x 2) LEED pattern appears for the sample with the thinnest deposited Cc layer (2.4 angstrom). For samples with thicker Ce-films, the LEED pattern co-exists of a c(2 x 2) structure and a more diffuse 6% contracted (2 x 1) structure. This appears at the same temperature as the Ce3d and Rh3d core levels exhibit sharp intensity changes and binding energy shifts.The intensity of the f(0), f(1) and f(2) multiplets in the Ce 3d core level spectra change when the annealing temperature is increased. The relative intensity of the Ce3d f(0) and f(2) features compared to the Ce 3d f(1) features is largest after annealing to 500 degrees C. This is below the temperature at which the ordered surface alloy is formed. When the sample is heated above the formation temperature of the surface alloy, the relative intensity of the Ce 3d f(0) and f(2) features decrease. (C) 2007 Elsevier B.V. All rights reserved.

The deposition and annealing in ultra high vacuum (UHV) of 5-6 monolayers (ML) of cerium on clean reconstructed Si-face 4H-SiC (0001) is studied by x-ray photoemission spectroscopy (XPS). Band bending as a function of annealing was studied by shifts of the bulk peak contribution in the C1s and Si2p spectra relative to the clean reconstructed surface. Additional datapoints for Schottky barrier formation on 4H-SiC are thus obtained by the low work function rareearth metals, and presented in the framework of the metal-induced-gap states and electronegativity model. A Ce/CeSi2-x/4H-SiC interface alloy forms by annealing to 850-1050oC. Kinetic information from the oxidation of the Ce/CeSi2-x/4H-SiC interface alloy is also reported. In particular, a SiO2- x/Ce-Si mixed oxide/4H-SiC forms upon oxidation. The shift of the C1s SiC-bulk-peak towards higher binding energies upon oxidation indicates that the mixed Ce-Si oxide interface layer appears to passivate the near Fermi-level 4H-SiC interface states at least as well as SiO2, and are expected to modify the electrical interface characteristics.