Ba0.6Sr0.4TiO3 (BST) ferroelectric thick films were grown on MgO(001) and Al2O3 (0 0 0 1) single-crystal substrates by using a pulsed laser deposition method. Structural, morphological, optical, and terahertz characterization of the BST films were performed by X-ray Diffraction, Atomic Force Microscopy, Spectroscopic Ellipsometry (SE), and Terahertz Time-Domain Spectroscopy (THz-TDS). Single-phase samples with strong preferred (1 1 1) orientation and surface roughness lower than 1.5% of their thicknesses have been obtained for both types of substrates. SE was employed to extract the thickness and optical properties by using a 3-layer optical model (substrate/thin film/roughness). The inferred refractive index @630 nm is around 2.05, while the optical interference is visible until 3.3 eV. The THz-TDS measurements in transmission set-up were carried out one after the other on substrates before and after the BST film deposition. The standard THz-TDS analysis of double-layer samples proved difficult to complete in the cases in which a thin or thick film is deposited on a much thicker substrate of known dielectric properties. However, we have been able to extract the complex dielectric permittivity in the THz domain for BST samples with thicknesses of few microns, by developing a specific procedure of data analysis.

Despite intensive investigations in the UV (ultraviolet) and visible range, the research on the optical properties of graphene in the extended near and mid infrared range by means of Spectroscopic Ellipsometry (SE) remains limited yet. Herein, the optical properties of a Chemical Vapor Deposition (CVD)-grown monolayer graphene, transferred from a copper substrate onto SiO2/Si, were studied in the broad energy range (0.38-6.2 eV) using Variable Angle Spectroscopic Ellipsometry (VASE). The morphological and the structural properties of the samples were investigated by Micro-Raman Spectroscopy, Wavelength Dispersive X-ray (WDX) analysis, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The Lorentz oscillator model proposed for the optical response of graphene fits very well the experimental data. An unintentional doping, revealed by Micro-Raman Spectroscopy and WDX, is reported.

The evaluation of thickness, refractive index, and optical properties of biomolecular films and self-assembled monolayers (SAMs) has a prominent relevance in the development of label-free detection techniques (quartz microbalance, surface plasmon resonance, electrochemical devices) for sensing and diagnostics. In this framework Spectroscopic Ellipsometry (SE) is an important player. In our approach to SE measurements on ultrathin soft matter, we exploit the small changes of the ellipsometry response (?? and ??) following the addition/removal of a layer in a nanolayered structure. So-called ?? and ?? difference spectra allow to recognize features related to the molecular film (thickness, absorptions) and to the film-substrate interface thus extending SE to a sensitive surface UV-VIS spectroscopy. The potential of ellipsometry as a surface spectroscopy tool can be boosted when flanked by other characterizations methods. The chapter deals with the combined application of broad-band Spectroscopic Ellipsometry and nanolithography methods to study organic SAMs and multilayers. Nanolithography is achieved by the accurate removal of molecules from regularly shaped areas obtained through the action of shear forces exerted by the AFM tip in programmed scans. Differential height measurements between adjacent depleted and covered areas provide a direct measurement of film thickness, which can be compared with SE results or feed the SE analysis. In this chapter we will describe the main concepts behind the SE difference spectra method and AFM nanolithograhy. We will describe how SE and AFM can be combined to strengthen the reliability of the determination of thickness and, as a consequence, of the optical properties of films. Examples will be discussed, taken from recent experiments aimed to integrate SE and AFM nanolithography applied to SAMs and nano layers of biological interest. By analysing in detail the changes of the spectroscopic features of compact versus non-compact layers and correlating such changes with the post-lithography AFM analysis of surface morphology SE unravels the specific versus unspecific adsorption of biomolecules on gold surfaces functionalized with suitable SAMs

Thin films of cerium dioxide (CeO2) were deposited by atomic layer deposition (ALD) at 250 degrees C on both Si and titanium nitride (TiN) substrates. The ALD growth produces CeO2 films with polycrystalline cubic phase on both substrates. However, the films show a preferential orientation along < 200 > crystallographic direction for CeO2/Si or < 111 > for CeO2/TiN, as revealed by X-ray diffraction. Additionally, CeO2 films differ in the interface roughness depending on the substrate. Furthermore, the relative concentration of Ce3+ is 22.0% in CeO2/Si and around 18% in CeO2/TiN, as obtained by X-ray photoelectron spectroscopy (XPS). Such values indicate a similar to 10% off-stoichiometry and are indicative of the presence of oxygen vacancies in the films. Nonetheless, CeO2 bandgap energy and refractive index at 550 nm are 3.54 +/- 0.63 eV and 2.3 for CeO2/Si, and 3.63 +/- 0.18 eV and 2.4 for CeO2/TiN, respectively. Our results extend the knowledge on the structural and chemical properties of ALD-deposited CeO2 either on Si or TiN substrates, underlying films differences and similarities, thus contributing to boost the use of CeO2 through ALD deposition as foreseen in a wide number of applications. (C) 2017 Elsevier B. V. All rights reserved.

We report an investigation of the graphene/substrate interface morphology in large-area polycrystalline graphene grown by chemical-vapour deposition and wet-transferred onto Si wafers. We combined spectroscopic ellipsometry, X-ray photoelectron spectroscopy and atomic-force microscopy in order to yield morphological and chemical information about the system. The data showed that wet-transferred samples may randomly exhibit nanosized relief patterns indicative of small water nanopockets trapped between graphene and the underlying substrate. These pockets affect the adhesion of graphene to the substrate, but can be efficiently removed upon a mild annealing in high vacuum. We show that ellipsometry is capable of successfully and reliably detecting, via multilayer dielectric modelling, both the presence of such a spurious intercalation layer and its removal. The fast, broadly applicable and non-invasive character of this technique can therefore promote its application for quickly and reliably assessing the degree of adhesion of graphene transferred onto target substrates, either for ex-post evaluation or in-line process monitoring.

We report the optical constants of graphene oxide and reduced graphene oxide determined by spectroscopic ellipsometry. The dynamic changes in optical properties and thickness of a drop-cast graphene oxide layer during reduction by long-term exposure to focused broad-band white light are monitored in situ. The anisotropic optical constants of the graphene oxide layer and the isotropically averaged optical constants of the reduced layer are precisely determined from a multiple-location analysis of spatially resolved data across the exposed location and a multiple-time-step analysis of the dynamic data, respectively. Observed inter-band transitions in the graphene oxide layer are discussed in relation to theoretical predictions for different coverage levels of the graphene oxide sheets with oxygen containing functional groups. The derived optical constants of the reduced graphene oxide layer are compared to reported values of graphene and thermally reduced graphene oxide.

Ion implantation proved to be an universal technique for producing waveguides in most optical materials. Tellurite glasses are good hosts of rare-earth elements for the development of fibre and integrated optical amplifiers and lasers covering all the main telecommunication bands. Er3+-doped tellurite glasses are good candidates for the fabrication of broadband amplifiers in wavelength division multiplexing around 1.55 ?m, as they exhibit large stimulated cross sections and broad emission bandwidth. Calcium fluoride is an excellent optical material, due to its perfect optical characteristics from UV wavelengths up to near IR. It has become a promising laser host material (doped with rare earth elements). Ion implantation was also applied to optical waveguide fabrication in CaF2 and other halide crystals. In the present work first single-energy implantations at 3.5 MeV at various fluences were applied. Waveguide operation up to 1.5 ?m was observed in Er:Te glass, and up to 980 nm in CaF2. Then double-energy implantations at a fixed upper energy of 3.5 MeV and lower energies between 2.5 and 3.2 MeV were performed to suppress leaky modes by increasing barrier width.

Bismuth germanate is a well known scintillator material. It is also used in nonlinear optics, e.g. for building Pockels cells, and can also be used in the fabrication of photorefractive devices. In the present work planar optical waveguides were designed and fabricated in eulytine (Bi4Ge3O12) and sillenite (Bi12GeO20) type bismuth germanate crystals using single- and double-energy irradiation with N+ ions in the 2.5 < E < 3.5 MeV range. Planar waveguides were fabricated via scanning a 2 mm × 2 mm beam over the waveguide area. Typical fluences were between 1 o 1015 and 2 o 1016 ions/cm2. Multi-wavelength m-line spectroscopy and spectroscopic ellipsometry were used for the characterization of the ion beam irradiated waveguides. Waveguide structures obtained from the ellipsometric data via simulation were compared to N+ ion distributions calculated using the Stopping and Range of Ions in Matter (SRIM) code. M-lines could be detected up to a wavelength of 1310 nm in the planar waveguide fabricated in sillenite type BGO, and up to 1550 nm in those fabricated in eulytine type BGO.

In situ spectroscopic ellipsometry is employed to investigate the adsorption of Yeast Cytochrome c (YCC) on SiO2/Si substrates. In order to highlight the slight variations induced by protein adsorption, difference spectra (???? and ????) have been considered, following the approach introduced in our previous studies on self-assembled monolayers. The difference spectra show a sharp dip at about 410 nm, the Soret or B band, related to the heme optical absorption, whose fine position is sensitive to the protein environment and to the oxidation state of the iron ion within the heme. Remarkably, the analysis of the difference spectra allowed us to detect two lower intensity dips in the 590-650 nm range, the Q bands, whose position and lineshape provide additional information on protein conformation and redox state. Quantitative reproduction of experimental data obtained by using a simple isotropic optical model, accounting for the molecular absorption spectrum, is presented. Estimates of the film thickness and determination of the position and shape of the heme-related features were obtained from calculations. The results are compared with those previously obtained in a study on YCC adsorption on Au substrates. Complementary ex-situ atomic force microscopy measurements are also presented.

Nickel silicide is considered the best candidate material to achieve the lowest contact resistance in sub 45 nm CMOS devices. NiSi films with thickness 20-60 nm were prepared by rapid thermal annealing of Ni (temperature 230 °C-780 °C) on top of thin 230 nm silicon-on-insulator substrates, with a constant formation ratio. Based on film independent characterizations, a novel model for the interpretation of spectroscopic ellipsometry data, featuring a combination of two Lorentzian oscillators and one Drude dispersion model, is proposed, and its goodness is checked in comparison to other known models. This new approach is proved to deliver more accurate estimation of the film thickness and resistivity. © 2012 American Institute of Physics.

Ion implantation, compared with other waveguide fabrication methods, has some unique advantages. It has proved to be a universal technique for producing waveguides in most optical materials. The authors of the present article reported fabrication of channel and slab waveguides in an Erbium-doped tungsten tellurite glass by implantation of MeV energy N + ions. The present article reports successful adaptation of the same technique to the fabrication of slab waveguides in eulytine type bismuth germanate (BGO) and CaF 2 crystals. This is the first report on successful waveguide fabrication in these materials using 3.5 MeV N + ions at implanted fluences between 5 × 10 15 and 4 × 10 16 ions/cm 2. Spectroscopic ellipsometric measurements revealed the existence of guiding structures in both materials. M-line spectroscopic measurements indicated guiding effect in the as-implanted BGO up to 1550 nm and up to 980 nm in the as-implanted CaF 2. Ion implantation induced the appearance of three peaks in the UV/Vis absorption spectrum of CaF 2, that can be attributed to colour centres. © 2011 Elsevier B.V. All rights reserved.

Au nanoparticles (NPs)/(n-type)a-Si:H/(p-type)c-Si heterojunctions have been deposited combining plasma-enhanced chemical-vapour deposition (PECVD) with Au sputtering. We demonstrate that a density of similar to 1.3 x 10(11) cm(-2) of Au nanoparticles with an approximately 20 nm diameter deposited onto (n-type)a-Si:H/(p-type)c-Si heterojunctions enhance performance exploiting the improved absorption of light by the surface plasmon resonance of Au NPs. In particular, Au NPs/(n-type)a-Si:H/(p-type)c-Si show an enhancement of 20% in the short-circuit current, J(SC), 25% in the power output, P(max) and 3% in the fill factor, FF, compared to heterojunctions without Au NPs. Structures have been characterized by spectroscopic ellipsometry, atomic force microscopy and current-voltage (I-V) measurements to correlate the plasmon resonance-induced enhanced absorption of light with photovoltaic performance

This paper discusses the fundamentals, applications, potential, limitations, and future perspectives of polarized light reflection techniques for the characterization of materials and related systems and devices at the nanoscale. These techniques include spectroscopic ellipsometry, polarimetry, and reflectance anisotropy. We give an overview of the various ellipsometry strategies for the measurement and analysis of nanometric films, metal nanoparticles and nanowires, semiconductor nanocrystals, and submicron periodic structures. We show that ellipsometry is capable of more than the determination of thickness and optical properties, and it can be exploited to gain information about process control, geometry factors, anisotropy, defects, and quantum confinement effects of nanostructures.

Fabrication of channel waveguides in Er-doped tungsten-tellurite glasses was recently demonstrated. In order to get a deeper understanding of the process and to optimize the characteristics of the waveguides, we fabricated a set of planar waveguides, each of 7 mm × 7 mm lateral dimensions, in an Er-doped tellurite glass sample by implantation of 1.5 MeV nitrogen ions. Doses of the implanting ions ranged from 1 · 10 16 to 8 ·10 16 ions/cm 2. The samples were studied using interference phase contrast microscopy (Interphako), m-line spectroscopy and spectroscopic ellipsometry. The results show that a barrier layer of reduced refractive index was created around the range of the implanted ions at every dose. It is hoped that combination of the results obtained in these experiments with simulations for channel waveguides will make it possible to optimize ion-implanted fabrication of integrated optical components in this tellurite glass.

Abstract: In this article, we investigate the effects of oxygen partial pressure in the deposition chamber on the optical properties of zinc oxide (ZnO) thin films; in particular, we examine the variation of the refractive index with oxygen flux. ZnO thin films were deposited by radio-frequency (RF) magnetron sputtering and studied by means of X-ray diffraction (XRD) and spectroscopic ellipsometry (SE). We have found a preferential c-axis growth of ZnO films, with slightly variable deposition rates from 2.6 to 3.8 angstrom/s. Conversely, the refractive index exhibits, from ultraviolet (UV) to near infrared (IR), a considerable and almost linear variation when the oxygen flux value in the deposition chamber varies from 0 to 10 sccm.

A series of polystyrene (PS) and fullerene (C60) based thin films containing from 23 to 60 wt.% in fullerene were investigated. Initially, the films were characterised by Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy where the characteristic absorption bands of both the fullerene and the polystyrene were revealed. The additional characteristic absorption bands due the grafted fullerene to polystyrene were revealed as well. The relative peak intensities provided with qualitative information of the films stoichiometry in terms of the fullerene's amount that was grafted to polystyrene. The optical properties of the films were investigated by spectroscopic ellipsometry (SE). It was found that the increase of the fullerene's amount that was grafted to polystyrene results in an increase of the absorption coefficient ?, refractive index n, extinction coefficient k as well as in the dielectric constant ?? within the range between 2.4 and 2.8 for the lower and higher fullerene content, respectively. The films' J-V characteristics, of the space charge limited current (SCLC) behaviour, showed increased currents with increasing the fullerene's content. The electron mobility was extracted and found to increase with increasing the fullerene amount, from 4 × 10- 9 cm2/V s to 2 × 10- 7 cm2/V s. © 2005 Elsevier B.V. All rights reserved.

Nanostructured thin oxide films of SnO2, V2O5 and indium tin oxide (ITO) were deposited by conventional and plasma-assisted chemical vapor deposition (CVD, PECVD) on different substrates and at different temperatures. Optical properties of the films were determined by spectroscopic ellipsometry in the energy range 1.5–5.5 eV. A parameterized analysis, based on Lorentzian oscillators combined with the Drude model, along with Bruggeman effective-medium approximation (BEMA) modeling, was used to determine the optical constants of thin films independently from the reference dielectric functions of the bulk materials. In this way, correlation between the optical properties and nanostructure of thin films could be established. In particular, in order to discuss the dependence of optical constants on grain size, SnO2 nanostructured films have been considered, using a parameterization based on a double Lorentzian oscillator. Nanocrystalline V2O5 thin films have demonstrated the correlation between optical constants (described by four Lorentzian oscillators) and crystallineyamorphous volume fractions. Finally, ITO thin film optical properties are described by a combination of a double Lorentzian oscillator with the Drude model; by this analysis, gradients in the structural and optical properties of ITO are demonstrated.

In this paper, a spectroscopic ellipsometry (SE) study was carried out on V2O5 nanocrystalline thin films grown by plasma enhanced chemical vapor deposition. Both the real and imaginary part of the complex dielectric function and, hence, the refractive index and absorption coefficients, were described up to a photon energy of 5 eV, taking into account the anisotropy of vanadium pentoxide and the influence of the films microstructure on the optical properties. A novel approach based on a suitable combination of Lorentzian oscillators was used to describe the V2O5 optical properties. The effect of experimental parameters, such as deposition temperature and substrate, on the film microstructure and optical properties was investigated.