Die ellipsometrische Lichtstreuung wird als eine neue, leistungsfähige Methode zur Charakterisierung von Schichten um kolloidale Partikel vorgestellt. Theoretische Grundlage der Methode ist die Mie-Theorie der Lichtstreuung. Experimentell wurde die Polarisationsoptik eines Null-Ellipsometers in den Strahlengang eines Lichtstreuaufbaus eingebaut. Wie in der Reflexionsellipsometrie um den Brewsterwinkel herum erhält man in der ellipsometrischen Streuung einen Winkelbereich, in dem die Methode empfindlich auf Schichten an der Oberfläche der Partikel ist. An verschiedenen Systemen wurde die Tauglichkeit der ellipsometrischen Streuung zur Charakterisierung von Schichten auf Partikeln demonstriert. So wurden Dicke und Brechungsindex einer thermosensitiven Schicht von Poly(N-isopropylacrylamid) auf einem Poly(methylmethacrylat)-Kern bestimmt. Damit ist es möglich, experimentell den Schichtbrechungsindex und damit den Quellungsgrad zu bestimmen. Des Weiteren wurde der Einfluss der NaCl-Konzentration auf die Polyelektrolythülle von Poly(methylmethacrylat)-Poly(styrolsulfonat)-Blockcopolymer-Partikeln untersucht. Die Polyelektrolytketten liegen im hier untersuchten Beispiel nicht gestreckt vor. Als drittes wurde die Verteilung von niedermolekularen Ionen um elektrostatisch stabilisierte Poly(styrol)-Latexpartikel in Wasser untersucht. Hier wurde gezeigt, dass die beobachteten Schichtdicken und Schichtbrechungsindizes viel größer sind, als nach der klassischen Poisson-Boltzmann-Theorie zu erwarten ist. Des Weiteren wurde die Doppelbrechung von unilamellaren Lipidvesikeln bestimmt. Außerdem wurden Messungen der dynamische Lichtstreuung im Intensitätsminimum der Ellipsometrie durchgeführt. Dabei wird ein Prozess mit einer Korrelationszeit, die unabhängig vom Streuvektor, aber abhängig von der verwendeten Wellenlänge ist, sichtbar. Die Natur dieses Prozesses konnte hier nicht vollständig geklärt werden. / Ellipsometric light scattering is introduced as a new and powerful technique to characterize layers on colloidal particles. For the experiments, the polarization optics used reflection ellipsometry was installed in the beam of a light scattering setup. Using the priciples of null ellipsometry, a small range of scattering angles is obtained, were the method is sensitive to layers on the surface of colloidal particles. This is an analogy to the layer sensitivity of reflection ellipsometry at planer interfaces close to the Brewster angle. The theoretical basis for ellipsometric scattering is the Mie theory with its modern supplements. The feasibility of characterizing layers on colloidal particles was demonstrated with several systems. First, layer thickness and layer refractive index of poly(N-isopropylacrylamide) layers on a poly(methylmethacrylate) core were determined. This was the first time that the refractive index and with that the degree of swelling of a layer was directly determined in an scattering experiment. Second, polyelectrolyte layers on Poly(methylmethacrylate)-Poly(styrenesulfonate)-blockcopolymer particles were characterized. The influence of the salt concentration on the parameters of the layer was determined. The results show that the polyelectrolyte chains in the system investigated are not streched. Third, layers of ions around electrostatically-stabilized poly(styrene) particles were characterized. The layer thickness and layer refractive index in these examples are shown to be much larger than predicted by the classical Poisson-Boltzmann-theory. In addition, the birefringence of lipid vesicles was determined. Another interesting application of the ellipsometric scattering is the dynamic light scattering with ellipsometric optics. Its results show a characteristic process with a correlation time independent of the scattering vector, but wavelength dependent. The origin of this mode is not yet completely clarified.

The aim of the work presented in this thesis is to contribute to a fundamental understanding of polarizing phenomena in some scarab beetles. The aim is also to study the beetle structures as inspiration in fabrication of artificially sculptured films. The three investigated species Cetonia aurata, Potosia cuprea and Liocola marmorata are of the family Scarabaediae and subfamily Cetoniianae (Guldbaggar). They were all collected at Swedish locations and are the only species of Cetoniinae scarabs in Sweden. This work reports on their optical properties represented by Mueller matrix elements, degree of polarization data and trace curves in the Cartesian complex plane representation of polarized light. From these results we verifyan earlier structural model for the Cetonia aurata and make way for similar models of the other two species. The ellipsometer used in this work is of dual rotating compensator type from which the complete Mueller-matrix for the medium examined can be obtained. The ellipsometric measurements were conducted on the scutellum for four different angles of incidence, 45°, 55°, 65° and 75° over a wave-length range of 245-1000 nm. Common for all examined species is that left polarization is observed in the wavelength range of 400 800 nm. For most of these species the polarization state is close to circular at some wavelengths especially at smaller angles of incidence. In general the degree of polarization is high (above 50%) when the polarization is near-circular. The degree of polarization also shows a clear dependence on the angle of incidence. The earlier model for Cetonia aurata shows a good agreement with the experimental data of this work. The model is also found as a good basis to work from to create models for the other two species.

Due to increasing problems with bacterial resistance development, there is a growing need for identifying new types of antibiotics. Antimicrobial peptides constitute an interesting group of substances for this purpose, since they are believed to act mainly by disrupting the bacterial membrane, which is a fast and non-specific mechanism. In order to understand the details on this action simplified phospholipid model membranes based on liposomes, monolayers and bilayers, were employed in this thesis. By in situ ellipsometry studies on supported lipid bilayers in combination with leakage from liposomes it was found that peptide-induced membrane rupture to a great extent is related to peptide adsorption. The peptide activity and mechanism of action is highly dependent on peptide properties such as length, topology, charge, and hydrophobicity. Electrostatic interactions are crucial for peptide adsorption, whereas α-helix formation is of less importance, demonstrated by the dominating peptide conformation being random coil both in absence and presence of membranes, as investigated by circular dichroism. Comparable effects were observed in both mono- and bilayer systems, showing that formation of transmembrane structures is no prerequisite for membrane rupture by complement-derived peptides. Electrochemical studies on these peptides further demonstrated that hydrophobic interactions facilitate peptide penetration into the membrane, causing defects in close proximity to the peptides, while strong electrostatic interactions arrest the peptide in the headgroup region. Increasing the peptide hydrophobicity, by e.g., tryptophan end-tagging, also increases salt resistance. Good correlations were found between model membrane investigations and antibacterial activity towards both Gram-negative and Gram-positive bacteria, showing that membrane rupture is a key mechanism of action for the peptides investigated. In addition, for all peptides investigated cell toxicity is low.

This dissertation is focused on theoretical and experimental studies of optical properties of materials and multilayer structures composing liquid crystal displays (LCDs) and electrochromic (EC) devices. By applying spectroscopic ellipsometry, we have determined the optical constants of thin films of electrochromic tungsten oxide (WOx) and nickel oxide (NiOy), the films’ thickness and roughness. These films, which were obtained at spattering conditions possess high transmittance that is important for achieving good visibility and high contrast in an EC device. Another application of the general spectroscopic ellipsometry relates to the study of a photo-alignment layer of a mixture of azo-dyes SD-1 and SDA-2. We have found the optical constants of this mixture before and after illuminating it by polarized UV light. The results obtained confirm the diffusion model to explain the formation of the photo-induced order in azo-dye films. We have developed new techniques for fast characterization of twisted nematic LC cells in transmissive and reflective modes. Our techniques are based on the characteristics functions that we have introduced for determination of parameters of non-uniform birefringent media. These characteristic functions are found by simple procedures and can be utilised for simultaneous determination of retardation, its wavelength dispersion, and twist angle, as well as for solving associated optimization problems. Cholesteric LCD that possesses some unique properties, such as bistability and good selective scattering, however, has a disadvantage – relatively high driving voltage (tens of volts). The way we propose to reduce the driving voltage consists of applying a stack of thin (~1µm) LC layers. We have studied the ability of a layer of a surface stabilized ferroelectric liquid crystal coupled with several retardation plates for birefringent color generation. We have demonstrated that in order to accomplish good color characteristics and high brightness of the display, one or two retardation plates are sufficient.

Optical properties of copper oxide nanoparticles in a silica matrix thin film have been investigated. Films were prepared on Si substrates from a sol-gel by spin coating. Four samples with different thicknesses, from 14,5-109 nm, were fabricated. Optical properties were measured with Variable Angle Spectroscopic Ellipsometry. The aim of the project was to gain further understanding of these films that are interesting in applications for solar absorbers as solar selective coatings. Ellipsometricangles Ψ and Δ were measured in the wavelength range from 250-1700 nm. A dispersion model was developed and fitted to experimental data with acceptable results.

Two main subjects, ellipsometry and computer screen photo-assisted techniques (CSPT), form the main line in this thesis. Ellipsometry is an optical technique based on the detection of polarization changes of light upon interaction with a sample. As most optical detection techniques it is non-intrusive and an additional advantage is its high surface sensitivity: thickness resolution in the order of pm can in principle be achieved. Therefore, ellipsometry is widely used as a technique for determination of optical constants and layer thickness for thin-layer structures. Lately ellipsometry has also been proposed for sensing applications, utilizing the detection of changes in the properties of thin layers. One application is described in this thesis concerning the detection of volatile organic solvents in gas phase using modified porous silicon layers, fabricated by electrochemical etching of silicon to create nm-sized pores. This greatly increases the surface area, promoting gas detection because the number of adsorption sites increases. Other applications of ellipsometry discussed in this thesis are based on combination with CSPT. CSPT is a way to exploit existing optical techniques for use in low-cost applications. In CSPT the computer screen itself is used as a (programmable) light source for optical measurements. For detection a web camera can be used and the whole measurement platform is formed by the computer. Since computers are available almost everywhere, this is a promising way to create optical measurement techniques for widespread use, for example in home-diagnostics. Since the only thing that needs to be added is a sample holder governing the physical or chemical process and directing the light, the cost can be kept very low. First, the use of CSPT for the measurement of fluorescence is described. Fluorescence is used in many detection applications, usually by chemically attaching a fluorescent marker molecule to a suitable species in the process and monitoring the fluorescent emission. The detection of fluorescence is shown to be possible using CSPT, first in a cuvette-based setup, then using a custom designed micro array. In the latter, polarizers were used for contrast enhancement, which in turn led to the implementation of an existing idea to test CSPT for ellipsometry measurements. In a first demonstration, involving thickness measurement of silicon dioxide on silicon, a thickness resolution in the order of nm was already achieved. After improvement of the system, gradients in protein layers could be detected, opening the door toward biosensor applications. Some further development will be needed to make the CSPT applications described here ready for the market, but the results so far are certainly promising.

Pagrindinis disertacijos tikslas – optinio ZnMgRE (RE = Y, Ho, Er) kvazikristalų atsako tyrimais atskleisti jų elektroninės posistemės ypatumus. Disertaciją sudaro eksperimentiniai rentgeno-difrakciniai (XRD) ir optiniai spektroskopiniai tyrimai, kvazikristalų elektroninės posistemės modelio konstravimas ir teorinis jų optinio atsako aprašymas. Atliktais eksperimentiniais XRD tyrimais buvo siekiama atskleisti kvazikristalų atvirkštinės gardelės vektorius, apibrėžiančius potencinį kvazikristalinį lauką, veikiantį į elektroninę posistemę. Optiniai spektroskopiniai tyrimai buvo atlikti kombinuotu spektroskopinės elipsometrijos ir atspindžio spektroskopijos metodu, paremtu darbe pasiūlyta inkaro lango duomenų analizės schema. Naudotas spektroskopinių tyrimų metodas įgalino atskleisti patikimus ZnMgRE optinio laidumo spektrus plačioje, 0.01 – 6 eV, spektrinėje srityje. Darbe išplėstas ZnMgRE elektronų posistemės modelis, kuris anksčiau buvo pasiūlytas kvazikristalų fotoemisinio atsako analizei. Nepriklausomų Fermi paviršiaus sankirtų su Bragg’ų plokštumomis schema formuluota išplėstiniame juostiniame atvaizdavime. Teorinė optinio laidumo skaičiavimų schema, anksčiau pasiūlyta kristalinių junginių optinio laidumo skaičiavimams, šiame darbe išplėsta įskaitant įvairias Fermi lygmens padėtis pseudotarpo atžvilgiu. Teoriniai ZnMgRE optinio laidumo skaičiavimai, atlikti darbe pasiūlyto elektroninės posistemės modelio rėmuose, detaliai atkartoja eksperimentinius optinio laidumo spektrus... [toliau žr. visą tekstą] / The main goal of the dissertation was to reveal the electronic structure of ZnMgRE (RE = Y, Ho, Er) quasicrystals by investigations of their optical response. The thesis comprises experimental X-ray diffraction (XRD) and optical spectroscopy studies of the quasicrystals, a construction of their electron subsystem model, and a theoretical description of their optical response. The XRD studies were carried out to determine the reciprocal quasicrystalline lattice vectors, which define the atomic potential field acting on an electron subsystem. The optical spectroscopy studies were carried out by the combined spectroscopic ellipsometry and reflectance spectroscopy technique, based on a suggested anchor-window method. High-accuracy ZnMgRE optical conductivity spectra were recorded in the wide, 0.01 – 6 eV, spectral range. The model of ZnMgRE electron energy spectrum, previously suggested for an interpretation of experimental ZnMgRE photoemission spectra, was developed. The nearly-free-electron gas model of independent intersections was formulated in the extended zone presentation. A scheme of the theoretical optical conductivity calculations was extended to account for various positions of the Fermi level with respect to a pseudogap. The experimental ZnMgRE optical conductivity spectra can be reproduced in detail by theoretical calculations performed within the framework of the suggested electron energy spectrum model. The set of the electron energy spectrum parameters determined... [to full text]

The main goal of the dissertation was to reveal the electronic structure of ZnMgRE (RE = Y, Ho, Er) quasicrystals by investigations of their optical response. The thesis comprises experimental X-ray diffraction (XRD) and optical spectroscopy studies of the quasicrystals, a construction of their electron subsystem model, and a theoretical description of their optical response. The XRD studies were carried out to determine the reciprocal quasicrystalline lattice vectors, which define the atomic potential field acting on an electron subsystem. The optical spectroscopy studies were carried out by the combined spectroscopic ellipsometry and reflectance spectroscopy technique, based on a suggested anchor-window method. High-accuracy ZnMgRE optical conductivity spectra were recorded in the wide, 0.01 – 6 eV, spectral range. The model of ZnMgRE electron energy spectrum, previously suggested for an interpretation of experimental ZnMgRE photoemission spectra, was developed. The nearly-free-electron gas model of independent intersections was formulated in the extended zone presentation. A scheme of the theoretical optical conductivity calculations was extended to account for various positions of the Fermi level with respect to a pseudogap. The experimental ZnMgRE optical conductivity spectra can be reproduced in detail by theoretical calculations performed within the framework of the suggested electron energy spectrum model. The set of the electron energy spectrum parameters determined... [to full text] / Pagrindinis disertacijos tikslas – optinio ZnMgRE (RE = Y, Ho, Er) kvazikristalų atsako tyrimais atskleisti jų elektroninės posistemės ypatumus. Disertaciją sudaro eksperimentiniai rentgeno-difrakciniai (XRD) ir optiniai spektroskopiniai tyrimai, kvazikristalų elektroninės posistemės modelio konstravimas ir teorinis jų optinio atsako aprašymas. Atliktais eksperimentiniais XRD tyrimais buvo siekiama atskleisti kvazikristalų atvirkštinės gardelės vektorius, apibrėžiančius potencinį kvazikristalinį lauką, veikiantį į elektroninę posistemę. Optiniai spektroskopiniai tyrimai buvo atlikti kombinuotu spektroskopinės elipsometrijos ir atspindžio spektroskopijos metodu, paremtu darbe pasiūlyta inkaro lango duomenų analizės schema. Naudotas spektroskopinių tyrimų metodas įgalino atskleisti patikimus ZnMgRE optinio laidumo spektrus plačioje, 0.01 – 6 eV, spektrinėje srityje. Darbe išplėstas ZnMgRE elektronų posistemės modelis, kuris anksčiau buvo pasiūlytas kvazikristalų fotoemisinio atsako analizei. Nepriklausomų Fermi paviršiaus sankirtų su Bragg’ų plokštumomis schema formuluota išplėstiniame juostiniame atvaizdavime. Teorinė optinio laidumo skaičiavimų schema, anksčiau pasiūlyta kristalinių junginių optinio laidumo skaičiavimams, šiame darbe išplėsta įskaitant įvairias Fermi lygmens padėtis pseudotarpo atžvilgiu. Teoriniai ZnMgRE optinio laidumo skaičiavimai, atlikti darbe pasiūlyto elektroninės posistemės modelio rėmuose, detaliai atkartoja eksperimentinius optinio laidumo spektrus... [toliau žr. visą tekstą]

The overall thrust of this project is to gain an insight into a class of surface-tethered cross-linked thin films of poly(N-alkylacrylamides) that display a lower critical solution temperature (LCST).The structure of the alkyl group and the modification of the amide groups determine the LCST and resultant volume-phase transition behavior. The aim of this study involves synthesis and characterization of thin films and to correlate the volume-transition behavior to the structure of the alkyl group. For better understanding the volume-transition behavior, the polymer films are perturbed by the Hofmeister salt series to examine trends between different alkyl groups. While most of the studies have been done with bulk gels, the majority of the applications require the use of gels at surfaces and interfaces. Surface attached polymer networks provide an alternative to bulk gels showing superior response times, thus efficiency. Hence it is significant to understand the impact of confinement on the phase transition behavior of a polymer network. Anchoring a polymer network to a surface produces volume phase transition perpendicular to the substrate. The parallel swelling and collapse of the network is highly restricted due to lateral confinement, thus impacting properties such as structure, mechanical properties, dynamics and permeability of the network. Several studies have been done with poly(N-isopropylacrylamide) anchored to a substrate, which have shown significantly different behavior than unconstrained networks. Notable examples include a gradual as opposed to a sharp volume-phase transition, and significantly less swelling above and below the LCST. These studies only looked at poly(NIPAAm); therefore it remains unknown if these results are universal and will apply to other LCST polymers. Hence, we expanded upon these studies to also investigate a library of different LCST polymers belonging to the category of N-alkylacrylamides. I have synthesized the copolymers comprising of N-alkylacrylamides and methacryloxybenzophenone (MaBP). The benzophenone moiety in MaBP is photoreactive, allowing us to cross-link the copolymers by UV irradiation. Surface attached thin films were fabricated by spin coating the solution of copolymers and cross-linking by UV irradiation. The volume phase transitions of the coatings were studied under the influence of temperature and the salts of the Hofmeister series. Information concerning the state of responsive layers, the precise temperature at which the collapse occurs, and the changes in the molecular environment during the transition were investigated by ellipsometry and ATR-FTIR. In a longer perspective, understanding the transition behavior and the influence of salts governing this transition provides a better understanding of the interactions of biopolymers in natural systems.

Ce manuscrit de thèse présente une étude expérimentale des propriétés optiques, électroniques et structurales du diamant fortement dopé au bore. Ce semi-conducteur à large bande interdite peut être synthétisé par dépôt chimique en phase vapeur assisté par plasma micro-onde (MPCVD). Il est intrinsèquement isolant mais devient métallique, voire supraconducteur conventionnel par dopage de type p. Ce travail s'articule autour de trois grands axes :Le premier concerne le développement de l'ellipsométrie spectroscopique pour la caractérisation de couches de diamant monocristallin. Dans un premier temps, des modèles optiques ont été développés afin de déduire les épaisseurs, résistivités et concentrations de porteurs de plusieurs séries d'échantillons mesurés ex situ. Ces valeurs ont été confrontées à celles obtenues par le biais de mesures SIMS (Spectroscopie par Emission d'ion Secondaires) et de transport électronique. Une masse effective optique des porteurs a pu ainsi être évaluée. Dans un second temps, cette technique a été mise en oeuvre in situ sur le réacteur. L'influence de la température et de la géométrie de la chambre de réaction a été évaluée et des suivis de croissance en temps réel sont présentés.Le second axe porte sur la synthèse des échantillons et l'optimisation des paramètres de croissance. Dans cette partie, nous révélons la présence d'un transitoire dans l'incorporation du bore conduisant à une inhomogénéité de dopage des échantillons. Une augmentation de l'incorporation du bore avec le débit a également été observée pour la première fois. Enfin, la détérioration de la qualité cristalline du diamant, au delà d'une concentration critique d'atomes de bore, est identifiée et discutée.Le troisième et dernier axe de ces travaux de recherche, est dédié à l'investigation des propriétés électroniques du diamant fortement dopé par magnéto-transport de 300K à 50 mK. Dans un premier temps, l'importance de la mésa-structuration de croix de Hall lors des mesures de transport est mise en évidence. L'utilisation d'une géométrie « maîtrisée », permet en effet de limiter les courants parasites dus à l'inhomogénéité de dopage des couches. Nous avons ainsi pu construire un diagramme de phase différent de celui qui avait été rapporté dans la littérature. Une phase métallique et non supraconductrice a été mise en évidence pour la première fois. Une étude de la transition métal-isolant est présentée, et les exposants critiques issus de sa modélisation sont discutés. L'étude de l'état supraconducteur enfin, nous a permis d'aboutir à une nouvelle dépendance de la température de transition (Tc) avec le dopage. Cette dernière est comparée aux calculs ab initio de la littérature. Aucune réduction de la Tc avec l'épaisseur n'a en revanche été observée dans la gamme des couches synthétisées à savoir de 10 nm à 2 µm. / This PhD thesis reports on an experimental study of optical, electronic and structural properties of heavily boron-doped diamond. This wide bandgap semiconductor can be synthesized by Plasma Enhanced Chemical Vapor (MPCVD). Diamond is an insulator that may turn metallic and even superconductor (conventional) upon p-type doping.This work can be divided into three main parts :The first one involves the development of spectroscopic ellipsometry for characterizing single crystal diamond epilayers. First, optical models have been developed to derive the thickness, resistivity and carrier concentrations of several sets of samples measured ex situ. These values were then compared to those obtained through SIMS profiles (Secondary Ion Mass Spectroscopy) and transport measurements. As a result, an optical effective mass of carriers was determined. Second, this technique has been implemented to be set up in situ on the reactor. The influence of the temperature and the geometry of the growth chamber has been evaluated, and real time growth monitoring was achieved.The second part is related to the sample synthesis and optimization of growth parameters. In this section, we reveal the presence of a transient regime in the boron incorporation leading to a doping inhomogeneity. An increase of boron incorporation with the gas flow was also observed for the first time. Finally, the deterioration of the crystalline structure of diamond, above a critical dopant concentration, was identified and discussed.The third axis of this research is dedicated to the investigation of the electronic properties of heavily doped diamond by magneto-transport from 300K to 50 mK. First, the importance of the Hall bar mesa patterning for transport measurements is stressed. The use of a “controlled” geometry limited parasitic currents associated with doping inhomogeneities. Thus we could construct a new phase diagram, differing from previous reports in the literature. A metallic and non-superconducting layer has been unveiled for the first time. A study of the metal-insulator transition is reported and the critical exponents deduced from its modelling are discussed. Finally, the study of the superconducting state revealed a new dependence of the transition temperature (Tc) on doping which is compared with ab initio calculations. However, not any significant reduction of Tc was observed when the layer thickness dropped from 2 µm to 10 nm.