A great deal of attention has been paid to brown carbon aerosol in the troposphere because it can both scatter and absorb solar radiation, thus affecting the Earth’s climate. However, knowledge of the optical and chemical properties of brown carbon aerosol is still limited. In this thesis, we have investigated different aspects of the optical and physicochemical properties of various brown carbon aerosol samples of potential atmospheric importance. First, reactions involving the di-carbonyl species methylglyoxal (MG) have been previously suggested as an important pathway for the production of secondary organic aerosol (SOA) in the atmosphere. Reaction in an aqueous inorganic salt solution, such as ammonium sulfate (AS), leads to the formation of light-absorbing brown carbon (BrC) product. In this thesis work, we employed a variety of experimental approaches to investigate the optical and physicochemical properties of BrC aerosol generated from this AS-MG reaction (BrC (AS/MG)). Optical properties of the dried BrC (AS/MG) aerosol particles were studied by Fourier transform infrared (FTIR) extinction spectroscopy in the mid-infrared region, cavity ring-down spectroscopy (CRDS) at 403 nm in the visible, and by measuring the light scattering phase function and polarization profiles at two different visible wavelengths, 532 and 402 nm. In addition, we used UV−vis spectroscopy to measure the mass absorption coefficient (MAC) of the solution-phase reaction products. The different optical properties were measured as a function of reaction time for a period of up to 22 days. The UV-vis absorption spectra showed a clear increase in measured MAC in the visible and near UV as the solution aged. However, analysis of the light scattering data showed no significant differences between AS and BrC aerosol in the derived refractive indices at either 532 or 402 nm, even for the longest reaction times. The FTIR extinction spectra was modeled in a Mie theory simulation to derive the complex refractive index in the mid-IR range (7000-800 cm−1); the results showed no significant changes in either the real or the imaginary parts of the refractive indices for BrC (AS/MG) aerosol particles when compared to unreacted AS aerosol. From the CRDS extinction data, the optical constants for BrC (AS/MG) particles at 403 nm were also determined through a Mie theory based analysis. The retrieved real index of refraction at 403 nm is n = 1.551 ± 0.005, with an imaginary index value of k = 0.000 ± 0.002; these values do not appear to change significantly with aging time over the course of 22 days and are not markedly different from the AS aerosol values. The small imaginary index value suggests that BrC (AS/MG) aerosol formed from this pathway may not significantly contribute to warming. In addition, CRDS measurements of the BrC (AS/MG) aerosol extinction at 403 nm as a function of particle size show a significant deviation from Mie theory simulations for particles with diameters of ≳500 nm, probably as a result of non-spherical particle shape effects. We also employed atomic force microscopy (AFM)-based IR spectroscopy to investigate the morphology and chemical composition of single SOA particles. AFM analysis of the particle morphology shows that a significant fraction of BrC (AS/MG) particles with diameters of ≳500 nm are non-spherical in shape, consistent with our observed breakdown in the applicability of Mie theory for larger particles. In addition to these measurements, we have characterized additional physicochemical properties of the BrC (AS/MG) aerosol particles including hygroscopic growth using a tandem-differential mobility analyzer. Compared to AS, BrC aerosol particles are found to have lower deliquescence relative humidity (DRH), efflorescence relative humidity (ERH), and hygroscopic growth at the same relative humidity values. Second, we investigated the optical properties of the water soluble products of limonene BrC generated from ozonolysis of d-limonene with further aging by AS. Optical constants for the dried limonene BrC aerosol product were measured at 403 nm by CRDS over the course of 9 days of aging. While the fresh limonene BrC aerosol showed a significant non-zero absorption index, the aged samples showed absorption index values consistent with zero. This result was somewhat unexpected because UV-vis absorption spectra of the bulk reaction solution showed a continued increase in absorption as the solution aged. One possible explanation for this result is that there could be an increase in the fraction of volatile chromophores as the solution ages, that are then removed in the aerosol drying process. Third, we investigated optical properties and chemical compositions of several humic substance (HS) reference samples including humic acid (HA) and fulvic acid (FA) standards by CRDS, UV-vis spectroscopy, elemental analysis, and 13C NMR spectroscopy. Measurements of the optical properties of HS is important in atmospheric science, because it is thought that HS samples have similar optical properties to organic materials, such as HUmic-Like Substances (HULIS), that exist in clouds, fogs, rainwater, and atmospheric aerosol. The humic acid aerosol samples generally showed higher absorption index values than the fulvic acid aerosol samples. We also found a correlation between the absorption index and chemical composition, with the value for k generally increasing with both increasing carbon-to-oxygen atomic ratio and sample aromaticity. In addition, we compared our measured optical constants for the HS aerosol samples with results from previous studies of field collected HULIS. The absorption index values for the fulvic acid aerosol samples give a better match than the humic acid samples when compared to the results from the field collected samples. Overall, these studies provide new details of the optical and physicochemical properties of a class of brown carbon organic aerosol which may have important implications for atmospheric chemistry and climate.

The use of solar cells for energy production has indeed a bright future. Reduction of cost for fabrication along with increased efficiency are key features for a market boom, both achieved as a result of increased knowledge of the technology. Especially the thin film solar cell technology with absorbers made of Cu(In,Ga)Se2 (CIGS) is promising since it has proven high power conversion efficiency in combination with a true potential for low cost fabrication. In this thesis different recipes for fabrication of the Cu(In,Ga)Se2 absorber layer have been studied. The deposition technique used has been co-evaporation from elemental sources. For all depositions the substrate has been heated to a constant temperature of 500 ºC in order for the growing absorber to form a chalcopyrite phase, necessary for the photovoltaic functionality. The selenium has been evaporated such to always be in excess during depositions whereas the metal ratio Cu/(In+Ga) has been varied according to different recipes but always to be less than one at the end of the process. In the work emphasis has been on the radiative properties of the CIGS film during growth. The substrate heater has been temperature controlled to maintain the constant set temperature of the substrate, regardless of varying emitted power caused by changing surface emissivity. Depending on the growth conditions the emissivity of the growing film is changing, leading to a readable variation in the electrical power to the substrate heater. Since the thermal radiation from the substrate during growth has been of central focus, this has been studied in detail. For this reason the substrate has been treated as an optical stack composed of glass/Mo/Cu(In,Ga)Se2/CuxSe which determine the thermally radiated power by its emissivity. An optical model has been adopted to simulate the emissivity of the stack. In order to use the model, the optical constants for Cu(In,Ga)Se2 and CuxSe have been derived for the wavelength interval 2 μm to 20 μm. The simulation of the emissivity of the stack during CIGS growth agreed well with what has been seen for actual growth. Features of the OP-signal could hereby be explained as a result of film thickness of Cu(In,Ga)Se2 and CuxSe respectively. This is an important knowledge for an efficient fabrication in large scale.

Zirconium carbide (ZrC) powders were produced by carbothermal reduction reactions using fine-scale carbon/metal oxide mixtures as the starting materials. The reactant mixtures were prepared by pyrolytic decomposition of solution-derived precursors. The latter precursors were synthesized via hydrolysis/condensation of metal-organic compounds. The first step in the solution process involved refluxing zirconium alkoxide with 2,4 pentanedione ("acacH") in order to partially or fully convert the zirconium alkoxy groups to a chelated zirconium diketonate structure ("zirconium acac"). This was followed by the addition of water (under acidic conditions) in order to promote hydrolysis/condensation reactions. Precursors with variable carbon/metal ratios were produced by varying the concentrations of the solution reactants (i.e., the zirconium alkoxide, "acacH," water, and acid concentrations.) It was necessary to add a secondary soluble carbon source (i.e., phenolic resin or glycerol) during solution processing in order to obtain a C/Zr molar ratio close to 3 (as required for stoichiometry) in the pyrolyzed powders. The phase development during carbothermal reduction was investigated for oxide-rich carbon-deficient and slightly carbon-rich compositions. The reaction was substantially completed after heat treatments in the range of ~1400-1500oC. The crystallite sizes were in the range of ~100-130 nm. However, some oxygen dissolved in the lattice and some free carbon was present. Heat treatment at temperatures >1600oC was required to complete the reaction. The dry-pressed powder compacts, with varying C/Zr molar ratios, were pressureless sintered to relative densities in the range of ~98-100% at 1950oC.

Silicon based hydrogenated amorphous semiconducting (intrinsic and n/p doped a-Si:H and a-Si1-xCx:H) thin films have been deposited by plasma enhanced chemical vapor deposition (PECVD) system. In order to analyze the optical response of these amorphous films, intrinsic optical absorption mechanisms have resumed and spectral variations of absorption coefficient &amp / #61537 / (E) are derived. The exponential variation of absorption coefficient for energies below the band edge is discussed in the frame of randomly distributed square well like potential fluctuations of localized states. Urbach constant EU and the slope B are deduced as disorder parameters. Both intensity sensitive transmittance and reflectance, and amplitude/phase sensitive ellipsometric techniques for multilayer thin films are theoretically and practically treated. Various methodologies are developed for the determination of thickness, refractive index and absorption coefficient of the films. A reflectance unit is adapted to the spectrometer and all the measuring instruments are computerized and relevant software packets have been developed. IR spectroscopy has been used for determination of mainly hydrogen concentrations and bonding properties. Establishing the production-characterization-improved growth conditions cycle successfully, the following results are obtained: (a) determination of lateral inhomogeneity of films along the radial direction of the plasma reactor, (b) determination of vertical inhomogeneity due to both substrate and air ambient, (c) perfect adjustment of refractive index and band gap of a-Si1-xCx:H films by changing carbon content of the films, (d) effect of plasma power density on both growth and carbon content.

The fundamentals of the ellipsometry are reviewed in order to point out the strengths and weaknesses of the ellipsometric measurements. The effects of the surface conditions (such as degree of cleanliness, contaminated thin layer, roughness etc&hellip / ) on the ellipsometric variables are experimentally studied / the optimum procedures have been determined. Hydrogenated amorphous silicon carbide (a-Si1-xCx:H) thin films are produced by plasma enhanced chemical vapor deposition (PECVD) technique with a circular reactor, in a way that RF power and carbon contents are taken as variables. These samples are analyzed using multiple angle of incidence ellipsometer and uv-vis spectrometer. These measurements have inhomogeneities in optical constants, such as thicknesses, refractive indices and optical energy gaps along the radial direction of the reactor electrode for different power and carbon contents.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 73-77).

Submitted by DIEGO ROSSI null (rossi_diego@ig.com.br) on 2016-02-16T18:58:22Z No. of bitstreams: 1 Dissertação D.Rossi - FINAL.pdf: 4611767 bytes, checksum: 71f830e143f447c9e962c2305462a623 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-02-17T16:11:21Z (GMT) No. of bitstreams: 1 rossi_d_me_bauru.pdf: 4611767 bytes, checksum: 71f830e143f447c9e962c2305462a623 (MD5) / Made available in DSpace on 2016-02-17T16:11:21Z (GMT). No. of bitstreams: 1 rossi_d_me_bauru.pdf: 4611767 bytes, checksum: 71f830e143f447c9e962c2305462a623 (MD5) Previous issue date: 2015-12-21 / Este trabalho tem por finalidade a deposição de filmes finos de carbono amorfo hidrogenado (a-C:H) e de filmes finos de carbono amorfo hidrogenado com silício (a-C:H:Si). Analisar a incorporação gradativa de cloro nos filmes, tornando-os clorados (a-C:H:Cl e a-C:H:Si:Cl). As técnicas utilizadas para a deposição dos filmes foram: (i) a deposição à vapor químico assistido por plasma (PECVD) e (ii) implantação iônica por imersão em plasma (PIIID). Os filmes foram produzidos a partir de misturas de vapores de propanol, CH3(CH2)2OH, vapores de tetrametilsilano, Si(CH3)4, vapores de clorofórmio, CHCl3, e argônio, Ar, respectivamente monômero 1, monômero 2, comonômero e gás plasmogênico. O aumento do clorofórmio na alimentação do reator acarretou em mudanças nas estruturas químicas do material depositado e também alterações nas suas características ópticas. Para averiguar as modificações nas propriedades ópticas dos filmes foram calculados o coeficiente de absorção, o índice de refração e o gap óptico com base em espectros de transmitância óptica na região do Ultravioleta, Visível e Infravermelho Próximo, (Uv/Vis/NIR). As modificações nas estruturas químicas dos filmes foram analisadas por espectroscopia de absorção no infravermelho por transformada de Fourier, FTIR, visando revelar os grupos químicos presentes nos filmes. Espectroscopia de fotoelétrons de raios X, (XPS), foi a técnica utilizada para desvendar a composição química elementar dos filmes e a 6concentração dos elementos presentes. As características de molhabilidade dos filmes foram medidas em um goniômetro, através da análise da interação da gota de um fluído com a superfície dos filmes. Espessuras medidas por perfilômetria foram comparadas a valores teóricos provenientes das constantes ópticas. Os resultados do XPS demonstraram a presença de cloro nos filmes, a concentração máxima obtida foi de ~ 8% at. Houve um aumento na taxa de deposição dos filmes em função do aumento da proporção de clorofórmio na entrada do reator. O ângulo de contato apresentou-se em torno de 75° para os filmes aC:H:Cl e em torno de 80° para os filmes a-C:H:Si:Cl. As análises ópticas Uv/Vis/NIR apresentaram índice de refração de ~1.5, calculadas por modelos computacionais iterativos, o gap de Tauc aumentou de 1,9 eV para 2,5 eV para filmes finos a-C:H clorados. / Thin hydrogenated amorphous carbon (a-C:H) and (a-C:H:Si) films were produced and the gradual incorporation of chlorine turn into a-C:H:Cl films and aC:H:Si:Cl films. The a-C:H:Cl and a-C:H:Si:Cl films were produced by plasma enhanced chemical vapor deposition (PECVD) from mixtures of vapor of propane, CH3(CH2)2OH, tetramethylsilane, Si(CH3)4, chloroform, CHCl3, and argon gas, Ar; respectively monomer 1, monomer 2, comonomer and argon gas. The increase of chloroform in the film composition resulted in changes in the chemical structure of the material and also changes in its optical characteristics. To investigate the changes in the optical properties of the films, the absorption coefficient, refractive index and band gap were calculated from optical transmittance spectra in the Ultraviolet, Visible and Near Infrared (Uv/Vis/NIR) regions. The modifications in chemical structures of the films were analyzed by Fourier transform infrared spectroscopy FTIR. X-ray photoelectron spectroscopy (XPS) was the technique used to measure the chemical composition of the films. The wettability characteristics were measured using a goniometer, through the analysis of the interaction of a fluid drop on the surface of the films. Film thicknesses were measured using perfilometry and compared with theoretical values derived from optical data. The XPS results showed chlorine in the film, and the maximum concentration was about 8% at. There was an increase in the deposition rate as 8chloroform proportion reactor inlet was added. The contact angle showed around 75° to a-C:H:Cl films and around 80° to a-C:H:Si:Cl films. The optical analyses Uv/Vis/NIR showed refractive index of ~1.5, calculated for interactive computer models. The Tauc band gap increased from 1,9 eV to 2,5 eV for a-C:H chlorinated films.

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<p>The fascinating optical properties of metallic nanostructures, dominated by collective oscillations of free electrons known as plasmons, open new opportunities for the development of devices fabrication based on noble metal nanoparticle composite materials. This thesis demonstrates a low-cost and versatile technique to produce stimuli-responsive ultrafast plasmonic nanostructures with reversible tunable optical properties. Albeit challenging, further control using thermal external stimuli to tune the local environment of gold nanoparticles embedded in VO2 host matrix would be ideal for the design of responsive functional nanocomposites. We prepared Au-VO2 nanocomposite thin films by the inverted cylindrical reactive magnetron sputtering (ICMS) known as hollow cathode magnetron sputtering for the first time and report the reversible tuning of surface plasmon resonance of Au nanoparticles by only adjusting the external temperature stimuli. The structural, morphological, interfacial analysis and optical properties of the optimized nanostructures have been studied. ICMS has been attracting much attention for its enclosed geometry and its ability to deposit on large area, uniform coating of smart nanocomposites at high deposition rate. Before achieving the aforementioned goals, a systematic study and optimization process of VO2 host matrix has been done by studying the influence of deposition parameters on the structural, morphological and optical switching properties of VO2 thin films. A reversible thermal tunability of the optical/dielectric constants of VO2 thin films by spectroscopic ellipsometry has been intensively also studied in order to bring more insights about the shift of the plasmon of gold nanoparticles imbedded in VO2 host matrix.</p>