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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.

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. Funding Agencies|Swedish Foundation for Strategic Research (Future Research Leaders 5); Nordforsk [9046]; Nordic Innovation Centre [09046]; European Research Council (ERC) under the European Communitys Seventh Framework Programme (FP)/ERC [335383]; Swedish Research Council (VR) [2012-4430]

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.

In this work we present reflectance imaging as a suitable method for in situ monitoring of the drying process of film formation for organic photovoltaics (OPV) over large areas, as well as for lab- ...

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.

Spectroscopic ellipsometry in the photon energy range from 0.04 eV to 6.50 eV is used for investigation of the optical response of Zn1-xBexTe crystals grown by a high-pressure Bridgman method in the composition range x ≤ 0.12. Infrared spectra display absorption bands centred between 411 cm−1 and 420 cm−1 associated with BeTe-type optical phonon modes. The positions of the transverse-optical and longitudinal-optical phonon modes have been found by modelling the line shape of the complex dielectric functions, e ˜ and Im ( − e ˜ − 1 ) , using a classical damped Lorentzian oscillator approach. Ellipsometric measurements in the VIS–UV range allow determination of the fundamental energy-gap (E0) and the higher threshold energies (E1, E1 + Δ1, E2) originating from the band edge and spin-orbit splitting critical points. We have found that the Be content x = 0.12 causes an increase of the fundamental energy gap about 0.15 eV at room temperature when compared to the E0 = 2.23 eV of ZnTe crystal at the same temperature. Photoluminescence spectra were measured in the temperature range from 30 K to room temperature. Luminescence at temperature T > 200 K is very weak. The peak positions of the exciton emission lines agree well with the E0 band-gaps derived from ellipsometric data if corrected for their temperature dependence.

Thin films of NixW1-x oxides with x = 0.05, 0.19, 0.43 and 0.90 were studied. Films with thicknesses in the range 125-250 nm were deposited on silicon wafers at room temperature by reactive DC magnetron co-sputtering from targets of Ni and W. The films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectroscopic ellipsometry (SE). XRD spectra and SEM micrographs showed that all films were amorphous and possessed a columnar structure. The ellipsometric angles psi and Delta of as-deposited films were measured by a rotating analyzer ellipsometer in the UV-visible-near infrared range (0.63-6.18 eV) and by an infrared Fourier transform rotating compensator ellipsometer in the 500-5200 cm(-1) wavenumber range. SE measurements were performed at angles of incidence of from 50 degrees to 70 degrees. Parametric models were used to extract thicknesses of the thin films and overlayers of NixW1-x oxide at different compositions, band gaps and optical constants. Features in the optical spectra of the NixW1-x oxides were compared with previous data on tungsten oxide, nickel oxide and nickel tungstate. 5th International Conference on Spectroscopic Ellipsometry, MAY 23-29, 2010,Albany, NY

Electrochromic films of tungsten oxide and nickel oxide were made by reactive dc magnetron sputtering and were characterized by X-ray diffraction, Rutherford backscattering spectrometry, scanning electron microscopy, and atomic force microscopy. The optical properties were investigated in detail by spectroscopic ellipsometry and spectrophotometry, using a multiple-sample approach. The W oxide film was modeled as a homogeneous isotropic layer, whereas the Ni oxide film was modeled as an anisotropic layer with the optical axis perpendicular to the surface. Parametric models of the two layers were then used to derive complex refractive index in the 300-1700-nm-range, film thickness, and surface roughness. A band gap of 3.15 eV was found for the W oxide film, using a Tauc-Lorentz parameterization. For the Ni oxide film, taken to have direct optical transitions, band gaps along the optical axis, perpendicular to it, and in an isotropic intermediate layer at the bottom of the film were found to be 3.95, 3.97, and 3.63 eV, respectively. Parameterization for the Ni oxide was made by use of the Lorentz model.

Effects of Ion Concentration on Refractive Indices of Fluids Measured by the Minimum Deviation Technique

Methodology for studies of effects of heating multilayers of human serum albumin (HSA) and anti-HSA is presented. Multilayers of anti-HSA were prepared on silicon substrates and studied with infrar ...

The optical properties of the azo-dyes SD-1/SDA-2, which are used for photoaligning of liquid crystals (LCs), are investigated with Variable Angle Spectroscopic Ellipsometry (VASE). Films of mixtur ...

Optical and compositional properties of In, In/Pd and Pd/In/Pd thin films evaporated on Cu and SiO2 substrates in vacuum were investigated by means of X-ray diffractometry, Auger electron spectroscopy and spectroscopic ellipsometry methods. Auger depth profile studies were performed in order to determine the composition of InCu and InPd structures. In both systems interdiffusion of metals was detected at room temperature. The XRD patterns indicated formation of CuIn2 and PdIn3 phases in the samples. Optical properties of the composite layers containing intermetallic phases were derived from ellipsometric quantities Ψ and Δ measured in the photon energy range 0.1-6.0 eV at different angles of incidence using suitable multilayer models for the examined samples.

Optical and luminescence properties of the Bridgman-grown Cd 1-x-y Be x Zn y Se and Zn 1-x-y Be x Mg y Se crystals are reported. Spectroscopic ellipsometry was employed for determination of spectral dependence of the complex dielectric function ?(E) in the photon energy range 0.75-6.5eV. Below the absorption edge the refractive indices n(E) of the alloys were modelled using a Sellmeier-type relation. The excitonic band-gap energies were estimated from the ellipsometric and photoluminescence measurements. Compositional effects in the ellipsometric and photoluminescence spectra are discussed.

Lattice absorption of Zn 1-x-y Be x Mg, Se and Cd 1-x-y Be x Zn y Se mixed crystals grown by a high pressure Bridgman method has been investigated by infrared spectroscopic ellipsometry in the wave number range from 230 cm to 5000 cm -1 . Ellip-sometric spectra of Cd 1-x-y Be x Zn y Se crystals display features in the spectral range 350-550 cm associated with BeSe-type phonon modes. In the optical spectra of Zn 1-x-y Be x Mg y Se crystals both BeSe-type and MgSe-type: lattice absorption bands are detected. The MgSe-like modes are located at approximately 300 cm -1 . The frequencies and oscillator strengths of optical phonon modes depend strongly on the alloy composition.

The optical properties in terms of dielectric function e(hSω)= e1(hSω)+ie2(hSω)of rocksalt pb 1-xsnx Te alloyes (0≤x≤1)are investigated experimentally by spectroscopic ellipsometry and theoreticall ...

Porous diamond-like-carbon (PDLC) thin films obtained on silicon substrate by DC low energy magnetron sputtering have been investigated by photoluminescence, transmission and reflection spectroscopy, photoacoustic and spectroscopic ellipsometry. The absorption features observed for these films show similarities with those of porous silicon (PS) as well as in the performed gradient structural pattern classification of the SFM porosity, by means of the computational GPA-flyby environment on PS and PDLC samples. The dielectric function is also calculated for the bulk diamond-like carbon using the full-potential linearized augmented plane wave method within the framework of local density approximation to density functional theory. From the measurement a low real dielectric constant of about 4.5 at 0.8 eV was found whereas the calculated e1(0) for the bulk diamond has a value of 5.5.

Silicon monoxide films were deposited on silver films on glass substrates and studied by infrared ellipsometry to determine the optical properties in the infrared wavelength range from 1.3 to 40 micrometers. The thicknesses of silicon monoxide and aluminum films were designed to 1 micrometer and 200 nanometers, respectively. The ellipsometric measurements were carried out by using a spectro-ellipsometer attached with an FT-IR. The imaginary part of the refractive index shows a high absorption region which is centered at 10 micrometers, whereas in other wavelength regions it shows rather low absorption. The resultant optical properties of silicon monoxide film are compared with published data. As an application, the spectral reflectance of spectral selective panel heating surface is calculated.

The refractive index N = n + ik of the protein bovine carbonic anhydrase (BCA) adsorbed in porous silicon layers is determined using infrared spectroscopic ellipsometry. Five absorption bands in the amide region are resolved. The distribution of the protein inside the porous matrix is modelled and it is found that more BCA per internal surface area are adsorbed in the upper part of the porous layer than in the bottom part.

Adsorption of human serum albumin in porous silicon gradients monitored by spatially-resolved spectroscopic ellipsometry

The present work aims to study preparation of thin MIP films on a gold-coated QCM resonator in a well-controlled and reproducible manner. A surface-bound photo-radical initiator was used to furnish an imprinting polymerization in a dilute solution of template, functional monomer and crosslinker. Prior to polymerization, the photo-initiator was covalently coupled to a self-assembled monolayer of carboxyl terminated alkanethiol on a gold surface. With this approach we were able to control the thickness of the MIP film to be below 50 nm, where the selective recognition of target analytes can be easily detected by the underlying quartz crystal resonator. When used in a flow injection analysis system, the assembled QCM sensor generated a large frequency change (> 30Hz) upon encountering a small amount of analyte (0.19 mM). The sensor had a very short response time (< 1 min), and displayed certain chiral selectivity towards the original template, (S)-propranolol at a concentration higher than 0.38 mM in aqueous solution. (c) 2004 Elsevier B.V. All rights reserved. (Less)

Optical properties related to lattice vibrations and photoluminecence of Zn 1− x Be x Se and Zn 1− x − y Be x Mn y Se alloys are presented. Optical phonons of the mixed crystals grown in a sphalerite phase for composition 0≤ x ≤0.35 and 0≤ y ≤0.22 have been investigated by IR spectroscopic ellipsometry in the wave number range 230–8000 cm −1 . The complex dielectric functions can be reproduced using a model with three classical damped oscillators corresponding to the BeSe-like modes and a Drude contribution from the free carriers. The zone-centre optical-phonon frequencies increase continuously with increasing Be concentration. The amplitudes of the vibrations are also increasing with Be content.

Interdiffusion of metals from group Ib (Ag, Cu) and group IIIb (In) was detected at room temperature by means of spectroscopic ellipsometry (SE) and Auger electron spectroscopy (AES). Thin In films and the In/Ag layers were deposited on Cu substrates by thermal evaporation in a vacuum of 3×10 −4 Pa. Optical properties of In–Cu and In–Ag composite layers formed due to interdiffusion were derived from ellipsometric quantities Ψ and Δ measured in the photon energy range 0.75–6.5 eV. Auger depth profile studies were performed in order to determine the composition of elements in the In/Ag/Cu and In/Cu systems.

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 th ...

Infrared to vacuum ultraviolet optical properties of 3C, 4H and 6H silicon carbide measured by spectroscopic ellipsometry

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.

Infrared spectroscopic ellipsometry for wave numbers from 333 to 4000 cm −1 is demonstrated as a useful technique for characterization of structural, vibrational, and free-charge-carrier properties of conducting organic thin layers deposited on electrically conducting as well as on isolating substrates. Pentacene and poly(3,4-ethylenedioxy thiophene)/poly(styrenesulfonate) (PEDOT:PSS) are studied exemplarily. For both materials, the infrared dielectric functions are reported, which can serve as fingerprints for multiple-layer structures analysis. PEDOT:PSS layers deposited onto n-type and p-type silicon substrates reveal different conductivity response, whereas the IRSE data show that the pentacene layers on glass are rendered highly resistive.

A technique combining ellipsometry with total internal reflection is presented. The method is called total internal reflection ellipsometry (TIRE) and is suitable for monitoring of internal surfaces which opens new possibilities for measuring adsorption on metal surfaces in opaque liquids. Results from measurements of adsorption of milk and subsequent cleaning with sodium hydroxide on metal surfaces are given. These include studies on gold, iron, and chromium surfaces. A schematic design of the instrument used in TIRE is included. The main advantages of the system are non-invasive probing, fast response, and high sensitivity. The method has potential for applications in monitoring of internal surfaces of pipelines in industrial processes.

Gas sensing was performed using spectroscopic ellipsometry and porous silicon films. Modification of the porous layer by polymer deposition showed an increase in sensitivity to organic solvent vapor of up to 135%. The increase in sensitivity is strongly dependent on polymer concentration. At high concentrations, too much polymer is deposited, presumably blocking the pores, causing a decrease in sensitivity. At sufficiently low concentrations, the polymer causes a strong increase in sensitivity. This is assumed to be caused by the polymer being deposited inside the pores, where its interaction with the vapor influences the sensitivity. At very low concentration, the sensitivity approaches values obtained without polymer modification. The sensitivity increase is different for different vapors, pointing to possible selectivity enhancement.

Cd 1-x Mn x Te crystals, obtained by the high-pressure Bridgman method for x = 0, 0.27, 0.49, 0.67 and 0.8, were investigated. Crystal composition was determined by electron microprobe analysis. For an Mn content lower than 0.7, a single phase of pure zinc blend structure was found. In Cd 0.2 Mn 0.8 Te samples a two-phase structure was revealed. Auger electron spectroscopy (AES) was used to determine the composition of the crystal surfaces. AES depth profiles obtained by argon sputtering and AES analysis allowed to find the distribution of Cd, Mn and Te inside the sub-surface region. Spectroscopic ellipsometry was applied to determine the complex dielectric function e of the samples. Ellipsometric measurements were performed at room temperature in the photon energy range 0.75-6.5 eV. The spectral dependence of e was used to find the energy gaps E g of the alloys with different Mn content. Ellipsometric data were correlated with the compositional results obtained from the electron microprobe and AES depth profile investigations. A linear increase of energy gaps with increasing x was observed for chemically homogeneous CdMnTe crystals.

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 the current density used during etching, the more sway-back shaped curves were seen for the protein adsorption pattern, independent of pH. When 50 mA/cm 2 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.

Ellipsometry has sufficient sensitivity for sensor applications and is here used as an optical readout method in a gas sensing system. Porous silicon is used as sensing layers in which vapors of solvents can adsorb and condensate due to capillary effects. A miniaturized multi-beam ellipsometer system is proposed and the concept is demonstrated by measurements on alcohol vapors. Optimization of the sensor system is discussed and improvement of sensitivity and alteration of selectivity by metal deposition in porous silicon layers are presented.

Infrared dielectric function spectra and phonon modes of high-quality, single crystalline, and highly resistive wurtzite ZnO films were obtained from infrared (300–1200 cm−1) spectroscopic ellipsometry and Raman scattering studies. The ZnO films were deposited by pulsed-laser deposition on c-plane sapphire substrates and investigated by high-resolution x-ray diffraction, high-resolution transmission electron microscopy, and Rutherford backscattering experiments. The crystal structure, phonon modes, and dielectric functions are compared to those obtained from a single-crystal ZnO bulk sample. The film ZnO phonon mode frequencies are highly consistent with those of the bulk material. A small redshift of the longitudinal optical phonon mode frequencies of the ZnO films with respect to the bulk material is observed. This is tentatively assigned to the existence of vacancy point defects within the films. Accurate long-wavelength dielectric constant limits of ZnO are obtained from the infrared ellipsometry anal...

MBE grown GaBiAs epitaxial layers with Bi content of 3.5%, 5.2%, and 7.5%, sandwiched between GaAs, have been investigated by spectroscopic ellipsometry in the infrared and absorption threshold spectral regions. The real and imaginary parts of the dielectric function of GaBiAs indicate bandgap Eg and spin-orbit splitting Δ0+ values close to literature data. The refractive index of GaBiAs in the IR region 0.2–0.8 eV exceeds that of GaAs by ca. 0.8%, 2.3%, and 3.6%, for Bi content 3.5 %, 5.2%, and 7.5%, respectively (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The sensitivities of porous silicon layers modified by copper deposition to low vapor concentrations of methanol, ethanol and 2-propanol are studied with spectroscopic ellipsometry. The porous silicon layers are prepared with electrochemical etching in hydrofluoric acid, and copper deposition is done in aqueous CuSO 4 . The ellipsometric vapor sensitivities, in terms of the ellipsometric spectral shifts due to gas exposures, of these samples and their oxides are studied and compared. It is shown that ellipsometric vapor sensitivities of porous silicon layers to alcohols are improved by copper deposition. It is also found that the oxidation of copper deposited in porous silicon layers shows improved selectivity to methanol.

Bacterial infection and inflammation result in massive changes in serum glycoproteins. These changes were investigated by the interaction of the saccharide glycoprotein moiety with lectins. A panel of eight lectins (Canavalia ensiformis, Bandeiraea simplicifolia BS-I, Arachis hypogaea, Phytolacca americana, Phaseolus vulgaris, Artocarpus integrifolia, Triticum vulgaris and Pisum sativum) was used to differentiate human serum glycoproteins obtained from patients with various bacterial infections. Lectin functionalised sensing layers were created on gold-coated wafers and lectin-glycoprotein interactions were monitored by surface plasmon resonance. The interaction of the lectin panel with serum glycoproteins produces unique patterns. Principal component analysis (PCA) was used to analyse the patterns. The actual panel of eight lectins enabled discrimination between sera obtained from patients sick with bacterial infection and healthy patients. Extended lectin panels have the potential to distinguish between types of bacterial infection and identify specific disease state. (Less)

Spectroscopic ellipsometry was used to determine the optical properties of plate-like hydrated tungsten trioxide (3WO3·H2O) films in the energy range 300–4000 cm− 1. Films with different thicknesses were deposited on glass substrates pre-coated with fluorine-doped tin oxide via an efficient and simple hydrothermal method. Parametric models were used to extract thicknesses and optical constants of the thin films. The WO3 was found to be more hydrated for thicker films. Moreover, the nano-plates are larger in thicker films, which leads to a decrease of the transmission due to an increase of the scattering. Features in the obtained dielectric functions of the 3WO3·H2O thin films were compared with the earlier published optical spectra of WO3 and its hydrates ½WO3·H2O and WO3·H2O.

Optical properties of bulk Cd1-xMgxSe mixed crystals, grown from a CdSe, Mg, and Se melt by the Bridgman method, are presented. The alloys have a wurtzite type structure in the investigated range o ...

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 -α-(2,5-dimethyl-3-furyl)-ethylidene(adamantylidene)succinic anhydride and ( E )-2-[α-(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

In this paper, properties of the Zn 1− X Be X Se crystals grown from the melt by the high-pressure Bridgman method are reported. Spectroscopic ellipsometry has been used for determination of the complex dielectric function of Zn 1− X Be X Se. On the basis of the photon energy dependence of the dielectric function, the energy gaps of alloys containing different beryllium concentrations have been evaluated. Measurements of the photoluminescence (PL) spectra allowed to find the excitonic gap in the investigated alloys. Auger electron spectroscopy (AES) with simultaneous argon ion sputtering has been used for determination of surface composition. AES investigations allowed to make predictions concerning distribution of particular elements in the samples.

A non-destructive method for investigation of pore size distribution and surface area of porous silicon is presented. Adsorption and desorption isotherms of water in thin films of porous silicon are analyzed using variable angle of incidence spectroscopic ellipsometry. The analysis is based on multilayer optical models and the Bruggeman effective medium approximation. Pore size distribution and surface area are extracted from the isotherms employing the Wheeler theory combined with the Kelvin and Cohan equations. Good agreement is obtained between the calculated pore size distribution and estimations made by scanning electron microscopy. The evaluated specific surface area for the porous layers presented here is ∼180 m 2 /cm 3 , which is in good agreement with the value reported in the literature.

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.

Porous silicon layers with thicknesses in the range 100-400 nm and average porosities in the range 38-71% were prepared by electrochemical anodization. Variable angle spectroscopic ellipsometry was ...

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 (m) homoepitaxial films.

Porous silicon Fabry-Perot optical filters with reflectivity peaks in the visible and near infrared spectral range have been manufactured electrochemically and characterized with variable angle spectroscopic ellipsometry. Generalized ellipsometry and the Bruggeman effective medium approximation were employed to study the anisotropy of the samples including determination of the tilt of the optic axis relative to the sample normal. At a wavelength of 700 nm, the difference between the real parts of the ordinary and extraordinary indexes of refraction of the low and high index sublayers were 0.05 and 0.07, respectively. In addition, the effect of temperature on the spectral redshifts caused by capillary condensation of water and toluene vapors in the porous material are investigated. It is demonstrated that a temperature decrease causes the spectral shifts to occur at lower partial pressures, indicating a more effective vapor capture at lower temperatures. Finally, it is shown that this phenomenon can be use...

Spectroscopic ellipsometry was employed to determine the complex dielectric functions of thin polycrystalline Cu films affected by diffusion of the Pd atoms from substrate through the film. The features observed in the optical absorption were analysed assuming additive contributions related to the Friedel–Anderson theory of virtual-bound-state (VBS) alloys and an effective medium microstructure. This procedure made it possible to estimate concentration of Pd in diffusive layers and to find the VBS parameters. Such a virtual level-shape parameters as half-width ( Γ =0.28 eV) and the distance in energy of the centre of VBS from the Fermi level of Cu ( E d =1.8 eV) do not differ much from those found for Ag/Pd couple.

Calculations of Hamaker constants using Lifshitz theory require the availability of accurate dielectric data, especially in the visible-ultraviolet region. We present spectroscopic ellipsometry data on well-defined cellulose films of a limited thickness range (100–140 layers) deposited on an oxidised and hydrophobised silicon substrate. The spectral data, representing measurements from a perpendicular orientation to the fibre deposition direction, was used for estimates of the necessary spectral parameters, i.e. the oscillator strengths and characteristic frequencies in the UV-range. Our calculations show that cellulose has a relatively low Hamaker constant in air (58 zJ) and water (8.0 zJ). The implications for the surface energy estimates of cellulose and colloidal interactions between cellulose and various types of fillers and coating colours are indicated.

The role of hydrochloric acid in the fabrication of porous silicon was investigated with atomic force microscopy (AFM) and spectroscopic ellipsometry. The study was focused on surface morphology, in terms of roughness and power spectral density (PSD), and layer microstructure and quality in terms of thickness, porosity, interface sharpness and layer homogeneity. The results show that HCl can be used as an additional component in the standard hydrofluoric acid-based etching solution in order to affect different properties of porous silicon layers such as volume porosity, thickness and pore size. In addition, HCl/HF mixtures can be used to obtain samples with sharper porous silicon/silicon interfaces and less in depth inhomogeneities as compared with porous silicon samples having similar volume porosities and thicknesses and manufactured in conventional solutions containing HF only. Whereas large variations in both thickness and volume porosity can be obtained by conventional solutions, the HCl/HF interplay yield large variations in one of the mentioned parameters only.

Optical properties of porous silicon superlattices are investigated using variable angle spectroscopic ellipsometry. Different phenomena such as in-depth inhomogeneities and interface transition regions are resolved and studied using various optical models. The optical properties of the samples are modified irreversibly by thermal oxidation yielding a blueshift of the reflectance. A reversible redshift of the spectra is obtained by vapor adsorption and liquid penetration into the superlattice. Moreover, existence of different specific internal surface areas and pore size distributions in the low and high index sublayers of the material is proposed.

Thin films of silicalite-1 grown on silicon substrates were studied by spectroscopic ellipsometry. Analysis of spectra using an optical model consisting of a single porous layer on silicon yielded ...

Variable angle spectroscopic ellipsometry was employed for multilayer characterization of thermally oxidized porous silicon layers and for quantitative adsorption studies of human serum albumin and fibrinogen in these layers. The oxidized samples were used either as prepared or were hydrated in a deionized water bath prior to their use. Hydration decreased the volume percentage of adsorbed albumin from 24 to 13% in the sublayer next to the ambient but resulted in an increase of the amount of adsorbed protein deeper in the film. Hydration did not, however, affect the adsorption behavior of fibrinogen which was found to adsorb only in the outermost sublayer. This phenomenon was attributed to the larger size of this protein. The amount of adsorbed fibrinogen depended on the concentration of the protein in the stock solution.