[Formulae and special characters can not be reproduced here. Please see the pdf version of the Abstract for an accurate reproduction.] Indium nitride is an important III-V nitride semiconductor with many potential applications such as in high frequency transistors, laser diodes and photo voltaic cells. The mobility and peak drift velocity of this material are predicted to be extremely high and superior to that of gallium nitride. However, many material properties such as the origin of the n-type conductivity and the electronic band gap are not well understood. Moreover, there is limited information on the stoichiometry and the level of impurity contaminations in the films from different growth techniques. The n-type conductivity observed for as-grown indium nitride films has long been attributed to nitrogen vacancies, implying that the material is nitrogen deficient. A band gap value around 2 eV, as measured by the optical absorption method, is suggested by some authors to be a result of the formation of an InNIn2O3 alloy. Alternatively, the observation of a lower absorption edge, suggesting a band gap around 0.7 eV, may be caused by Mie scattering at indium clusters that may form during film growth. Secondary ion mass spectroscopy and x-ray techniques provide only qualitative composition information. The quantitative interpretation of the results relies on calibration samples which are not available for indium nitride. In Rutherford backscattering spectroscopy, while quantitative, the carbon, nitrogen and oxygen signals cannot be separated unless the film is very thin ([tilde]150 nm). However, with heavy ion Elastic Recoil Detection (ERD) analysis all the elements in indium nitride films can be fully separated even for a film thickness of [tilde] 800 nm. In this work, indium nitride films from different growth techniques have been analysed with ERD using 200 MeV 197Au projectiles. The observed nitrogen depletion during the ERD analysis was monitored as a function of projectile fluence using a gas ionisation detector with a large solid angle. Different models have been tested and it has been shown that the bulk molecular recombination model accurately describes the nitrogen depletion so that the original nitrogen-to- indium ratio can be measured with an accuracy of [plus or minus]3 [percent]. The correlation of nitrogen depletion rate and stopping power of the projectile ion has been investigated. The study has shown that the rate of depletion is slower for low-Z projectiles. It has been shown that for a film with good structural properties, no loss of nitrogen occurs during the ERD analysis with low-Z projectiles such as 42 MeV 32S. Thus, the original nitrogen-to-indium ratio can be obtained without any theoretical modelling, and with a precision of better than [plus or minus]1 [percent]. All the indium nitride films studied in this work, for which X-ray diffraction shows no metallic indium, are nitrogen-rich which is contradictory to expectation. Therefore, the common assertion that nitrogen vacancies are the cause of n-type conductivity in as-grown films is diffcult to explain. Instead, the existence of In vacancies, N antisites and interstitial N2 may be speculated. The carbon and oxygen contamination is an issue for films grown by all common growth techniques. However, the suggested correlation of oxygen content in the film with the apparent band gap is not supported by the ERD results. Instead, a correlation between nitrogen-to-indium ratio and the measured band gap has been observed for films grown by RF-sputtering. This work reports the implantation of radioisotope probes using negative ions. The 111In/Cd probe was selected for this work as it is a common Perturbed Angular Correlation (PAC) probe and ideally suited for the study of indium nitride. For the synthesis of the probe 111In/Cd, several possibilities, such as the production of 111In/Cd via nuclear fusion evaporation reactions and from commercially available 111InCl3 solutions, were explored. Different materials, including powders of Al2O3 and In2O3, were investigated as a carrier for the probe in the ion source of the radioisotope implanter. It has been established that combining the 111InCl3 solution as the source and In2O3 powder as the carrier material gives optimum implantation efficiency. The radioisotope implanter facility has been developed to a stage that the radioisotope probe 111In/Cd can be routinely implanted into materials as molecular 111InO?? ions. An implantation rate of 3x10 4[th] Becquerel per hour has been demonstrated. Measurements on different materials (Ag, In, Ni, Si, InP) have shown that condensed matter spectroscopies such as Low Temperature Nuclear Orientation, Nuclear Magnetic Resonance on Oriented Nuclei (NMRON) and Perturbed Angular Correlation can be reliably performed. NMRON measurements on silver indicate a new resonance frequency of 75.08 MHz for 111InAg at 8.0 T. The local lattice environment of indium nitride thin films has been investigated with PAC spectroscopy. Several methods of introducing a radioisotope probe into a host material have been investigated for indium nitride. The thermal diffusion of the radioisotope probe 111In/Cd into indium nitride at a temperature below the dissociation temperature (about 550 [degrees] C) was not possible. The probe was, however, successfully introduced into indium nitride films with ion implantation techniques. Recoil implantation at MeV energies following fusion evaporation reactions and ion implantation at keV energies, both have been investigated for indium nitride films. An interaction frequency of v = 28 MHz has been measured for the 111In/Cd probe in indium nitride. This result is consistent with that obtained for indium nitride bulk grains. The PAC results suggest that all types of indium nitride films have a highly disordered lattice which could only be partially improved by annealing. Furnace annealing in nitrogen atmosphere above 400 [degrees] C resulted in the dissociation of the film. However, such dissociation could be avoided with rapid thermal annealing up to 600 [degrees] C. More detailed defect studies with PAC require the availability of better material. This study has also shown that indium nitride is highly sensitive to ion beam irradiation. Severe depletion of nitrogen during exposure to ions with MeV and KeV energies is an issue for the ion beam characterisation and processing of indium nitride.

Ternary chalcopyrite compounds are the semiconductors with suitable properties to be used as absorber materials in thin film solar cells. AgInSe2 is a promising candidate with its several advantages over the widely used CuInSe2. The purpose of this study was to optimize the physical properties of the Ag-In-Se (AIS) thin films that were deposited by e-beam evaporation of Ag3In5Se9 single crystal powder for solar cell applications by means of post-annealing process under nitrogen atmosphere. The as-grown AIS thin films were annealed at 200, 300 and 400oC and their structural, optical, electrical and photoelectrical properties were examined to observe the effects of post-annealing process. Structural characterization of the films was performed by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analyses. Optical properties of the films were investigated by optical transmittance measurements. Electrical and photoelectrical properties of the films were examined by temperature dependent conductivity, photoconductivity under different illumination intensities and spectral photoresponse measurements. It was discovered that the annealing of AIS thin films at 200oC resulted in the best physical properties for solar cell applications. The obtained films were polycrystalline with mixed binary and ternary crystalline phases, such as Ag3In5Se9, AgInSe2 and InSe, and showed n-type conductivity with room temperature conductivity value of 2.3x10-6 (Ohm&shy / cm)-1. The band gap energy of the 200oC-annealed films was determined as 1.68 eV from spectral photoresponse measurements. The results of the study revealed that the inadequate Ag incorporation and segregation and/or reevaporation of Se atoms at high annealing temperatures were the major problems encountered in producing single phase polycrystalline AgInSe2 thin films. The required stoichiometry of thin films should be maintained during the growth of the films by means of an alternative deposition procedure and the films should be selenized during post-annealing process.

[Formulae and special characters can not be reproduced here. Please see the pdf version of the Abstract for an accurate reproduction.] Indium nitride is an important III-V nitride semiconductor with many potential applications such as in high frequency transistors, laser diodes and photo voltaic cells. The mobility and peak drift velocity of this material are predicted to be extremely high and superior to that of gallium nitride. However, many material properties such as the origin of the n-type conductivity and the electronic band gap are not well understood. Moreover, there is limited information on the stoichiometry and the level of impurity contaminations in the films from different growth techniques. The n-type conductivity observed for as-grown indium nitride films has long been attributed to nitrogen vacancies, implying that the material is nitrogen deficient. A band gap value around 2 eV, as measured by the optical absorption method, is suggested by some authors to be a result of the formation of an InNIn2O3 alloy. Alternatively, the observation of a lower absorption edge, suggesting a band gap around 0.7 eV, may be caused by Mie scattering at indium clusters that may form during film growth. Secondary ion mass spectroscopy and x-ray techniques provide only qualitative composition information. The quantitative interpretation of the results relies on calibration samples which are not available for indium nitride. In Rutherford backscattering spectroscopy, while quantitative, the carbon, nitrogen and oxygen signals cannot be separated unless the film is very thin ([tilde]150 nm). However, with heavy ion Elastic Recoil Detection (ERD) analysis all the elements in indium nitride films can be fully separated even for a film thickness of [tilde] 800 nm. In this work, indium nitride films from different growth techniques have been analysed with ERD using 200 MeV 197Au projectiles. The observed nitrogen depletion during the ERD analysis was monitored as a function of projectile fluence using a gas ionisation detector with a large solid angle. Different models have been tested and it has been shown that the bulk molecular recombination model accurately describes the nitrogen depletion so that the original nitrogen-to- indium ratio can be measured with an accuracy of [plus or minus]3 [percent]. The correlation of nitrogen depletion rate and stopping power of the projectile ion has been investigated. The study has shown that the rate of depletion is slower for low-Z projectiles. It has been shown that for a film with good structural properties, no loss of nitrogen occurs during the ERD analysis with low-Z projectiles such as 42 MeV 32S. Thus, the original nitrogen-to-indium ratio can be obtained without any theoretical modelling, and with a precision of better than [plus or minus]1 [percent]. All the indium nitride films studied in this work, for which X-ray diffraction shows no metallic indium, are nitrogen-rich which is contradictory to expectation. Therefore, the common assertion that nitrogen vacancies are the cause of n-type conductivity in as-grown films is diffcult to explain. Instead, the existence of In vacancies, N antisites and interstitial N2 may be speculated. The carbon and oxygen contamination is an issue for films grown by all common growth techniques. However, the suggested correlation of oxygen content in the film with the apparent band gap is not supported by the ERD results. Instead, a correlation between nitrogen-to-indium ratio and the measured band gap has been observed for films grown by RF-sputtering. This work reports the implantation of radioisotope probes using negative ions. The 111In/Cd probe was selected for this work as it is a common Perturbed Angular Correlation (PAC) probe and ideally suited for the study of indium nitride. For the synthesis of the probe 111In/Cd, several possibilities, such as the production of 111In/Cd via nuclear fusion evaporation reactions and from commercially available 111InCl3 solutions, were explored. Different materials, including powders of Al2O3 and In2O3, were investigated as a carrier for the probe in the ion source of the radioisotope implanter. It has been established that combining the 111InCl3 solution as the source and In2O3 powder as the carrier material gives optimum implantation efficiency. The radioisotope implanter facility has been developed to a stage that the radioisotope probe 111In/Cd can be routinely implanted into materials as molecular 111InO?? ions. An implantation rate of 3x10 4[th] Becquerel per hour has been demonstrated. Measurements on different materials (Ag, In, Ni, Si, InP) have shown that condensed matter spectroscopies such as Low Temperature Nuclear Orientation, Nuclear Magnetic Resonance on Oriented Nuclei (NMRON) and Perturbed Angular Correlation can be reliably performed. NMRON measurements on silver indicate a new resonance frequency of 75.08 MHz for 111InAg at 8.0 T. The local lattice environment of indium nitride thin films has been investigated with PAC spectroscopy. Several methods of introducing a radioisotope probe into a host material have been investigated for indium nitride. The thermal diffusion of the radioisotope probe 111In/Cd into indium nitride at a temperature below the dissociation temperature (about 550 [degrees] C) was not possible. The probe was, however, successfully introduced into indium nitride films with ion implantation techniques. Recoil implantation at MeV energies following fusion evaporation reactions and ion implantation at keV energies, both have been investigated for indium nitride films. An interaction frequency of v = 28 MHz has been measured for the 111In/Cd probe in indium nitride. This result is consistent with that obtained for indium nitride bulk grains. The PAC results suggest that all types of indium nitride films have a highly disordered lattice which could only be partially improved by annealing. Furnace annealing in nitrogen atmosphere above 400 [degrees] C resulted in the dissociation of the film. However, such dissociation could be avoided with rapid thermal annealing up to 600 [degrees] C. More detailed defect studies with PAC require the availability of better material. This study has also shown that indium nitride is highly sensitive to ion beam irradiation. Severe depletion of nitrogen during exposure to ions with MeV and KeV energies is an issue for the ion beam characterisation and processing of indium nitride.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / PbS quantum dots has been grown in oxide glasses by two distinct methodologies according to the dopants, using the fusing method at 1200ºC. The host glass matrices used were SNAB (SiO2.Na2CO3.Al2O3.B2O3) and SNABP (SiO2.Na2CO3.Al2O3.B2O3.PbO2), with PbS bulk and S (sulphur) added as dopants, respectively. Thermal treatments were applied in a systematic way in order to allow a controlled growth of quantum dots. Different experimental techniques were realized in order to study the growth kinetic of dots as a function of thermal treatment times and dopant concentrations. It was analyzed thermal properties of the glass matrices by Calorimetry Scanning Diferencial (DSC). Many techniques have allowed discussion of the optical properties by Optical Absorption (OA) and Photoluminescence (PL), morphologic properties by Atomic Force Microscopy (AFM), and structural properties by X-Ray Diffractometry (DRX) of the nanocrystals. Qualitative and quantitative analyse of the chemical composition of the samples has been possible by spectrometry of Fluorescence of Raios-X (FRX). Using the ] 4 4 [ . × p k r r method we were able to estimate the avarage diameter of the PbS quantum dots. Calculations of dispersion sizes of PbS quantum dots, from the AO bands, has been presented. We have found the dependence between the quantum dot gap and the dopant concentrations. The relation between the Stokes Shift and the average size of the PbS quantum dots was also presented. Through the previous results, we have defined the methodology referring the host glass matrix SNABP with S bulk added as the most favorable to the growth PbS quantum dots with low size dispersion. / Pontos Quânticos de PbS foram sintetizados em vidros à base de óxidos, a partir duas metodologias distintas quanto a dopagens, pelo método da fusão a 1200ºC. As matrizes vítreas hospedeiras utilizadas foram: SNAB (SiO2.Na2CO3.Al2O3.B2O3) e SNABP (SiO2.Na2CO3.Al2O3.B2O3.PbO2), e os dopantes adicionados à elas foram PbS bulk e S (enxôfre), respectivamente. Tratamentos Térmicos variados e adequados foram efetuados nestas amostras para permitir o crescimento controlado dos pontos quânticos de PbS. Com o objetivo de estudar e acompanhar a cinética de crescimento destes pontos em função dos tempos de tratamentos térmicos e das variadas concentrações de dopantes, foram efetuadas várias técnicas de caracterizações. Estas permitiram análises das propriedades térmicas dos vidros por Calorimetria Exploratória Diferencial (DSC); ópticas, por Absorção Óptica (AO) e Fotoluminescência (PL); morfológicas, por Imagens de Microscopia de Força Atômica (AFM); e estruturais, por Difratometria de Raios-X (DRX) dos referidos nanocristais. Análises qualitativas e quantitativas das composições químicas das amostras sintetizadas neste trabalho foram possíveis através da técnica de espectrometria de Fluorescência de Raios-X (FRX). Com o auxilio do método ] 4 4 [ . × p k r r , foi possível estimar o diâmetro médio dos pontos quânticos de PbS. Cálculos de dispersão de tamanhos ξ a partir da largura a meia altura (W) das bandas de AO e discussões sobre a dependência de energia e o tamanho médio dos pontos quânticos foram apresentados e discutidos. Mostrouse graficamente a relação de dependência entre o Gap dos pontos quânticos e as concentrações de dopantes adicionados às matrizes vítreas. Apresentou-se de forma gráfica a relação entre o deslocamento Stokes e o tamanho médio dos pontos quânticos de PbS. A partir de análises dos resultados obtidos, definiu-se então a metodologia correspondente à matriz SNABP dopada com S bulk como sendo a mais favorável para a formação e crescimento dos pontos quânticos de PbS com menor dispersão de tamanhos entre si. / Mestre em Física

Este trabalho apresenta os resultados da construção de um espectrômetro utilizando a espectroscopia ótica por absorção diferencial (DOAS) para determinação de poluentes na atmosfera. A determinação e a quantificação de gases-traço contaminantes na atmosfera são possíveis pelo registro da transmitância, e posterior avaliação das estruturas de absorção características de cada espécie, em um caminho ótico aberto conhecido na atmosfera. As partes óticas e eletrônicas foram caracterizadas e o software de comando e processamento espectral foi desenvolvido. O sistema construído foi testado em laboratório e medidas de emissões veiculares de quatro automóveis foram realizadas. Os resultados das emissões veiculares apresentaram uma sensível diferença entre os veículos no regime de operação (motor frio e quente) por um fator que varia entre 5 e 8. / This work presents the results of the construction of a spectrometer using the differential optical absorption spectroscopy (DOAS) for determination of pollutants in the atmosphere. The determination and quantification of trace gas contaminations in atmosphere is possible by recording and later evaluation of characteristic absorption structures in a known path length in open atmosphere. The parts optics and electronic had been characterized and the software of command and spectral processing was developed. The system was built and tested in laboratory and vehicle emissions measures of four cars were performed. The results in vehicle emissions showed a noticeable difference between vehicles in the system of operation (hot and cold engine) by a factor ranging between 5 and 8.

Líquidos iônicos (LIs) são sais que se encontram no estado líquido em temperaturas menores que 100ºC e que vêm ganhando protagonismo na área chamada química verde, prometendo: substituir solventes nocivos ao meio ambiente, aprimorar componentes eletrônicos, favorecer biocatálises dentre outros. Sua alta estabilidade e baixa toxicidade são frequentemente afirmadas, porém, devem ainda ser melhor investigadas. Com o objetivo de implementar o entendimento da interação dos líquidos iônicos com sistemas de relevância biológica, realizamos um estudo sistemático acerca da interação de 3 diferentes líquidos iônicos anfifílicos de mesma cabeça polar e diferentes caudas carbônicas ([C10mim][Cl], [C12mim][Cl] e [C14mim][Cl]) com 3 diferentes proteínas modelo, através das técnicas de absorção óptica, fluorescência, dicroísmo circular (CD) e espalhamento de raios-X a baixos ângulos (SAXS). Para Tanto, utilizamos as proteínas BSA e HSA (Albuminas de Soro Bovino e Humano, respectivamente) além da lisozima. Observamos a supressão da fluorescência das proteínas em todos os casos analisados, onde a diminuição da intensidade correspondeu a, para as proteínas BSA, HSA e lisozima, respectivamente, (55±3)%, (16.1±0.8)% e (4.1±0.2)%, em presença de 0.6mM de [C14mim][Cl], (38±2)%, (13.2±0.7)% e (0.6±0.1)% em presença de 0.6mM de [C12mim][Cl] e (11.0±0.5)%, (9.2±0.5)% e (0.0±0.1)% em presença de 0.6mM de [C10mim][Cl]. Os espectros de absorbância e fluorescência de todos os sistemas nos indicam uma interação de contato entre as proteínas e os líquidos iônicos. Constatamos também o deslocamento do pico de fluorescência, das proteínas BSA e HSA, para menores comprimentos de onda (blue-shift), na medida em que a concentração de LI era aumentada. O máximo deslocamento () alcançado correspondeu a (21±1)nm para ambas albuminas, enquanto que a lisozima não apresentou deslocamento significativo. O blue-shift pode ser explicado pela aproximação das cadeias carbônicas e formações de pontes de hidrogênio nas proximidades dos triptofanos. De acordo com a técnica de SAXS, evidenciamos o aumento do raio de giro das proteínas, na medida em que adicionamos LIs. O raio de giro da BSA, da HSA e lisozima em ausência de LI são (29±1)Å, (30±1)Å e (15±1)Å, respectivamente, e passam para (46±1)Å, (44±1)Å e (20±1)Å respectivamente, em presença de 0.6mM de [C14mim][Cl]. As curvas de SAXS também apresentaram o indício da formação de estruturas micelares a partir de uma dada concentração. Além da alteração em sua estrutura terciária, os dados de CD indicam uma leve perda de estrutura secundária de ambas as albuminas (BSA e HSA), passando de 80 para 65% de -hélice em ausência e presença de 0.6mM de [C14mim][Cl], respectivamente. Sugerimos que as interações das proteínas com os líquidos iônicos, embora inicialmente movidas por forças eletroestática, possuem como principal fator o efeito hidrofóbico, portanto quanto maior a cadeia carbônica do LI maior é sua interação com a proteína. Tal interação causa o desenovelamento das proteínas e formação de um complexo e estruturas micelares a altas concentrações de LI. Acreditamos que este trabalho traz novas informações acerca da interação dos LIs com proteínas modelo, indicando sua capacidade de alterar a conformação das mesmas. / Ionic liquids (ILs) are salts that are liquid at temperatures smaller than 100 ° C and are gaining prominence in the so-called green chemistry, promising: replace harmful solvents to the environment, improve electronic components, and favor biocatalysis, among others. Its high stability and low toxicity are often asserted; nevertheless, they are ascribed to ILs due to its small volatility. With the aim of improving the understanding of the interaction of ILs with biological relevant systems, we conducted a systematic study of the interaction of three different ionic liquids of the same polar head and different paraffinic tails ([C10mim][Cl], [C12mim][Cl] and [C14mim][Cl]) with three different model proteins, through the techniques of optical absorption, fluorescence, circular dicrhoism (CD) and small angle X-ray scattering (SAXS). To do so, we use BSA and HSA proteins (Bovine Serum Albumin and the Human Serum Albumin, respectively) and lysozyme. We observed fluorescence quenching, of all studied proteins, where the decrease in the fluorescence was (for BSA, HAS and lysozyme, respectively): (55 ± 3)%, (16.1 ± 0.8)% to (4.1 ± 0.2 )% in the presence of 0.6mm [C14mim][Cl], (38 ± 2)%, (13.2 ± 0.7)% to (0.6 ± 0.1)% in the presence of 0.6mm [C12mim][Cl] and ( 11.0 ± 0.5)% (9.2 ± 0.5)% and (0.0 ± 0.1)% in the presence of 0.6mm [C10mim][Cl]. UV-vis absorbance spectra and fluorescence indicate all systems in a contact interaction between proteins and ionic liquids. We also note the shift of the fluorescent peak of BSA and HSA proteins for shorter wavelengths (blue-shift), as the IL content was increased. The maximum shift () achieved corresponded to (21 ± 1) nm for both albumins, whereas no significant displacement was observed for lysozyme. The blue-shift can be explained by the approach of carbon chains and formation of hydrogen bonds in the vicinity of tryptophan. SAXS data indicate an increasing in the proteins radius of gyration value as ILs was added in the solution. The turning radius of BSA, HSA and lysozyme in the absence of IL are (29 ± 1) Å, (30 ± 1) Å and (15 ± 1) Å, respectively, and go to (46 ± 1) Å, ( 44 ± 1) Å and (20 ± 1) Å, respectively, in the presence of 0.6mm [C14mim][Cl]. The SAXS curves also show evidence of the formation of micellar structures from a given concentration. Besides the change in its tertiary structure, the CD data indicates a slight loss of secondary structure of both albumins (BSA and HSA), from 80 to 65% of -helix in the absence and presence of 0.6mm [C14mim][Cl], respectively. We suggest that the interactions of the protein with the ionic liquid, although initially driven by electrostatic forces, have a major factor hydrophobic effect and thus the higher the carbon chain of greater IL is its interaction with the protein. This interaction causes unfolding of the protein and formation of a micellar structures at high concentrations of IL. We believe this work provides new information about the interaction of ILs with model proteins, indicating its ability to alter the conformation of the same.

Dotierung ist ein technologisches Schlüsselverfahren zur Kontrolle der Ladungsträgerdichte und der Position des Fermi-Levels in Halbleitern. Für organische Halbleiter hat sich die Verwendung von starken molekularen Elektronenakzeptoren und -donatoren als p- bzw. n-Dotanten als zuverlässigster Ansatz erwiesen. In der vorliegenden Arbeit wird eine Reihe von Themen im Zusammenhang mit der molekularen Dotierung von organischen Halbleitern untersucht. Zuerst wird die Eignung zweier verschiedener Materialparameter zur Vorhersage der Ionenpaarbildung bei der molekularen Dotierung überprüft: i) Redox-Potentiale, gemessen durch Cyclovoltammetrie (CV), und ii) Ionisationsenergie (IE) / Elektronenaffinität (EA), gemessen mittels (inverser) Photoelektronenspektroskopie (PES/IPES). Optische Absorptionsmessungen zeigen, dass Redox-Potentiale besser geeignet sind passende Materialpaare zu identifizieren als IE/EA-Werte. Zweitens wird die n-Dotierung eines prototypischen, p-artigen Co-Polymers durch metallorganische Dimere erforscht. Eine Kombination von PES/IPES, optischen Absorptions- und Leitfähigkeitsmessungen zeigt, dass das p-Polymer durch Dotierung zu einem n-Polymer transformiert werden kann. Drittens wird die p-Dotierung des Polymers P3HT durch ein bor-basiertes organisches Salz analysiert. Ein multi-experimenteller Ansatz zeigt die Bildung von Polaronen bei niedrigen und von Bipolaronen bei hohen Dotanten-Konzentrationen von über zehn Prozent. Zuletzt wird die Modifikation von elektronenselektiven Kontakten in organisch-anorganischen Metallhalogenid-Perowskit-Solarzellen (PSCs) untersucht, um Elektronensammel-Verluste zu minimieren. Hierzu wird eine Zwischenschicht aus metallorganischen Dimeren zwischen Elektrode und org. Elektronentransportschicht (ETL) eingebracht, um einen ohmschen Kontakt herzustellen. PSCs, die aus derart modifizierten elektronenselektiven Kontakte bestehen, weisen erhöhte Wirkungsgrade auf. / Doping is a key technological procedure to control the charge carrier density and Fermi level position in semiconductors. For organic semiconductors, the use of strong molecular electron acceptors and donors as p-type and n-type dopants, respectively, has emerged as the most reliable approach. In the present thesis, a variety of topics related to the molecular doping of organic semiconductors will be investigated. First, the suitability of two different material parameters to predict ion pair formation in molecular doping is explored: i) redox-potentials measured by cyclic voltammetry (CV) and ii) ionization energy (IE) / electron affinity (EA) measured by (inverse) photoelectron spectroscopy (PES/IPES). Optical absorption spectroscopy measurements reveal redox-potentials to be better suited to identify matching material pairs than IE/EA values. Secondly, the n-type doping of a prototypical p-type co-polymer by an organometallic dimer is studied. Combined PES/IPES, optical absorption and conductivity measurements show that the p type polymer can be rendered n-type upon doping. Thirdly, the p-type doping of the polymer P3HT by a boron based organic salt is investigated. A multi-experimental approach shows the formation of polarons at low and bipolarons at high dopant concentrations above ten percent. Finally, the modification of electron-selective contacts in organic-inorganic metal halide perovskite solar cells (PSCs) is studied in order to minimize electron collection losses. Here, an interlayer of organometallic dimers is introduced between electrode and organic electron transport layer in order to form an Ohmic contact. PSCs employing such modified electron-selective contacts show increased power conversion efficiencies.

Les fibres optiques utilisées pour le transfert d’information présentent des pertes de signal pendant leur propagation. Ainsi, ces signaux ont besoin d’être régulièrement amplifiés. De nos jours, l’Amplification Raman, basée sur le principe de diffusion Raman stimulée, est une des techniques utilisées pour réaliser ces amplifications. Les nanoparticules de métaux nobles ont des propriétés optiques uniques provenant de l’oscillation collective des électrons lorsqu’elles interagissent avec une onde électromagnétique. Ces particules absorbent fortement le champ électromagnétique à une fréquence appelée fréquence de résonance de plasmon de surface. Ce travail de thèse concerne l’influence des nanoparticules métalliques sur l’amélioration de l’Amplification Raman. Il s’inscrit dans le cadre du projet ANR Fenoptic (2010-2012), réunissant l’entreprise Draka et plusieurs laboratoires français (ICB Dijon, CMCP Paris, LPCML Lyon), qui s’intéressent à l’intégration des nanoparticules de métaux nobles à l’intérieur des fibres optiques afin d’utiliser la résonance de plasmon de surface pour améliorer l’efficacité des amplificateurs optiques. Dans ce travail, différentes sources de nanoparticules métalliques ont été examinées (suspensions, couches, préformes de fibre optique). Les expériences ont porté sur la caractérisation (forme et position du plasmon) de nanoparticules de métaux nobles incluses en matrices vitreuses ainsi que sur des mesures de spectroscopie Raman au travers desquelles le phénomène de Diffusion Raman Exaltée de Surface (SERS) a particulièrement été étudié. Pour la première fois, nous avons mis en évidence l’exaltation du signal Raman d’une matrice vitreuse. / Signals in optical fibers used for the transfer of information are attenuated due to impurities, scattering, absorption… To compensate for these losses, several techniques were developed like Erbium Doped Fiber Amplifier (EDFA). An alternative to rare earth doped fiber amplifier is Raman Amplification, which results from stimulated Raman scattering. Noble metal nanoparticles have optical properties induced by the collective oscillation of their conduction electrons when they interact with an electromagnetic wave. These particles strongly absorb the electromagnetic field at a frequency called surface Plasmon resonance frequency. This work is mainly based on effects leading to the improvement of the Raman Amplification. The ANR project Fenoptic (2010-2012), gathering Draka and several French laboratories (ICB (Dijon), CMCP (Paris), LPCML (Lyon)) is interested in the integration of noble metal nanoparticles in optical fibers using properties of the surface Plasmon resonance to improve the efficiency of optical amplifiers. In this work, different kinds of samples (suspensions, layers, optical fiber performs) with metal nanoparticles were studied. The experiments were based on the characterization (form and position of the Plasmon band) of noble metal nanoparticles in amorphous matrix and Raman spectroscopy was used to study the Surface Enhanced Raman Spectroscopy (SERS) effect. For the first time, we found the Raman signal exaltation of an amorphous matrix.

Uma amostra de zoisita natural proveniente da região de Teófilo Otoni Minas Gerais foi caracterizada pelas técnicas de termoluminescência (TL), ressonância paramagnética eletrônica (EPR) e absorção óptica (AO). As curvas de emissão TL das amostras natural e sob irradiação gama apresentaram picos em 130, 150, 265, 350 e 435 ºC todos eles com uma forte superposição. Tratamentos térmicos (TT) entre 500 e 900 °C afetaram muito pouco a estrutura cristalina da zoisita, no entanto os nove picos em 135, 155, 175, 200, 225, 255, 285, 320 e 360 ºC, ajustados teoricamente por deconvolução à curva experimental, apresentaram um máximo de sensibilidade TL para TT entre 600 e 700 ºC. O espectro de emissão TL contém uma banda intensa em torno de 310 nm e outra fraca em torno de 270 nm indicando que existem dois centros de recombinação que participam do processo de TL, o primeiro devido ao alumínio e o segundo devido ao titânio respectivamente. Exposições de amostras com TT em 600 °C à luz ultravioleta (UV) revelaram uma alta sensibilidade dos picos TL até 300 ºC, o que torna a zoisita um potencial candidato para aplicações em dosimetria de luz UV. A resposta TL da zoisita sob irradiação de raios gama, beta e elétrons de 1,4 MeV é similar, a única diferença está no aparecimento do pico em 110 ºC na irradiação com fonte beta. O espectro de EPR apresentou as seis linhas hiperfinas típicas do íon de Mn2+, em torno de g = 2,0, sobrepostas à linha da transição -1/2 -- +1/2 do Fe3+ num ambiente octaédrico. Além disso, dois conjuntos de linhas entre 800 - 1500 Gauss e 1500 - 2000 Gauss foram atribuídos aos íons de Cr3+ e Fe3+ respectivamente. Ambos íons sob ação de um forte componente axial de campo cristalino (CC), onde o nível fundamental 4A2 do íon de Cr3+ é desdobrado em dois dubletos mS = ±1/2 e mS = ±3/2. Os parâmetros de campo cristalino, Delta = 15100 cm-1, B = 739,5 cm-1 e D/B = 2,19 foram calculados a partir das transições permitidas de spin 4A2 -- 4T1 e 4A2 -- 4T2 do íon de Cr3+ na região visível do espectro de AO. A quebra do nível 4T2 foi atribuída à redução da simetria do poliedro Al(Cr)-O e à transição proibida de spin 4A2 -- 2T1 que sugere a substituição do Al3+ pelo Cr3+ na posição M3 da estrutura da zoisita. Bandas de AO devido a íons hidroxila e água foram identificadas na região do infravermelho próximo, todas elas estáveis frente a TT até 800 ºC e doses gama adicionais até 50 kGy. Baseado nos comportamentos dos centros de alumínio, titânio e E1 foi proposto um mecanismo de emissão TL. / Natural zoisite from the locality of Teófilo Otoni in the state of Minas Gerais - Brazil was investigated utilizing the techniques of thermoluminescence (TL), electron paramagnetic resonance (EPR) and optical absorption (OA). Natural as well as gamma irradiated zoisite exhibited TL peaks at 130, 150, 265, 350 and 435 ºC with an overlap of one peak with the other. Crystal structure of zoisite was found to be little affected by heat treatments in the range 500 - 900 °C. Deconvolution analysis has shown nine TL peaks at 135, 155, 175, 200, 225, 255, 285, 320 and 360 ºC. High TL sensitization has been observed for heat treated samples at 600 and 700 °C. The TL emission spectrum has shown a strong band around 310 nm and a weak one at 270 nm indicating the existence of two recombination centers, the first one due to aluminum and second one to titanium are involved in the TL process. Heat treated zoisite at 600 ºC exhibited high TL sensitivity of all TL peaks up 300 ºC. This feature indicates that zoisite can be a strong candidate for applications in UV dosimetry. The TL response of zoisite to beta rays and 1.4 MeV accelerated electrons is similar to that of gamma rays, with the exception that the electrons produced a 110 ºC peak. This peak was not seen under gamma irradiation. The EPR spectrum has shown the typical Mn2+ six hyperfine lines around g = 2.0. 1/ 2 to +1/ 2 transition line of the Fe3+ ion in an octahedral environment is also seen and the Mn2+ lines are overlapped by the Fe3+ line. On the other hand, most significant results have been observed in the low magnetic field region. Cr3+ lines are seen in the 800 - 1500 Gauss region and lines attributable to Fe3+ ion are observed in the 1500 - 2000 Gauss region. Both ions are under strong axial component of the crystal field (CF), where 4A2 state is split in two doublets mS = ±1/2 and mS = ±3/2. The crystal field parameters, Delta = 15100 cm-1, B = 739.5 cm-1 and Dq/B = 2.19 were calculated from the allowed spin transitions 4A2 -- 4T1 and 4A2 -- 4T2 of the Cr3+ ion in the visible region. The lifting of the 4T2 level was attributed to the lower polyhedron symmetry Al(Cr)-O and to the forbidden spin transition 4A2 -- 2T1; this suggests a substitution of Al3+ by Cr3+ ion at the site known as M3 in the structure of zoisite. Absorption bands due to OH and water molecule have been identified in the near infrared region. These bands have been found to be stable up to 800 ºC heat treatment and gamma doses up to 50 kGy. A model for the observed TL emission has been proposed based on the thermal annealing behaviour Al, Ti and E1 centers.

NLO materials have been researched for nearly five decades from the point of view of understanding the basic mechanisms and also in the pursuit of new materials possessing improved properties. Materials satisfying a set of physico-chemical properties such as wide transmission range, good mechanical hardness, high po-larizablity, noncentric crystal structure, good chemical stability, etc are the ones which are sought after. Several organic and inorganic molecules have been synthe-sized with the hope of finding materials that possess the desired NLO properties. Most of the organic materials are known to possess high figure of merit. However, their poor mechanical strength and needle like growth habit are hindrances to practical applications. Inorganic NLO materials have better mechanical properties but many of them possess small deff and laser induced damage threshold. Semi-organic NLO materials are intended to have the merits of both organic and inorganic counterparts. In this investigation, three important NLO crystals, viz cesium hydrogen L-malate monohydrate (CsLM, CsH[C4H4O5]H2O), cesium lithium borate(CLBO,CsLiB6O10)and near stoichiometric lithium niobate codoped with Nd and Zn (Nd:Zn:LiNbO3)are chosen for detailed study. The thesis is organized into 6 chapters. First chapter contains the theoretical background of the physical and chemical phenomena including a review of nonlin-ear optics, second harmonic generation, multiphoton absorption & refraction con-cepts, single crystal growth, principles of ferroelectricity and the scope of the work involved. For better connectivity, a brief review of the earlier work carried out on the chosen materials is given in the beginning of each chapter. The second chapter discusses the methodology of work and experimental details used in the present study. The third chapter deals with studies on CsLM, the new organometallic NLO crystal. Its structure, electro-optical properties and dielectric properties in FIR region are reported very recently. This material is also reported to show a phase transition at 50 0C though not much is understood about its nature. Further details of crystal growth conditions, nonlinear optical properties and laser damage thresholds are little known on this newly discovered NLO material. In this chapter detailed crystal growth studies and investigations of physical properties are presented. During growth, CsLM crystals manifest in platy and prismatic morphologies depending on level of super saturation invoked. The maximum dimensions of the grown crystal are 20 x15 x35 mm3. It has very good transmission in the range, 250-1300 nm and dislocation density of ≈104/cm2 . The dc conductivity measurements place this crystal between an ionic conductor and a dielectric. Dielectric properties show considerable frequency dispersion and axial anisotropy with є′ being the highest along the polar b axis. Maker fringes experiment reveals that CsLM possesses good second harmonic generation efficiency, an order of magnitude higher than KDP. It also has high laser damage threshold for fundamental and second harmonic wavelengths of Nd:YAG pulsed laser. TGA/DTA experiments are performed on the crystals grown below and above the reported transition temperature(labelled as CsLM and Anhydrous-CsLM respectively). The present investigations on Anhydrous-CsLM show that it crystallizes in a structure different from that of CsLM and the nature of the reported ′phase transition ′is driven by sluggish hydration and dehydration processes. Recently UV transparent nonlinear optical materials were evaluated for the fab-rication of all solid state UVlasers and CLBO is one such NLO material. It crystal-lizes in non-centrosymmetric tetragonal space group, I42d. It is highly transparent in the wide range of wavelengths from 180 to 2500 nm and has good deff. It pos-sesses very good angular and spectral bandwidth tolerances compared to its contemporaries such as lithium triborate(LBO) and beta barium borate(β-BBO). There is, however, a problem associated with this material that it cracks when exposed to atmosphere due to its hygroscopic nature. This chapter details the fabrication of the required instrumentation to grow single crystals of this material and the study of possible solutions to avoid cracking problem besides its new nonlinear properties. Since the melts of borate materials are known to be highly viscous, the crystal growth apparatus should have the options for tuning the parameters like seed and crucible rotation rates, temperature isotherms, slow pulling rate, etc. Keeping the above in mind, a high temperature top seeded solution growth unit was designed and fabricated inhouse. Highly transparent single crystals of CLBO were grown using the above unit which were characterized for the defects/dislocations using X-ray topography. The average dislocation density estimated is ≈103/cm2. The nonlinear optical absorption(NLA) and refraction(NLR) properties are studied. Z-scan experiments reveal that five photon absorption(5PA )is responsible for nonlinear absorption when the wavelength and pulse width are 800 nm and 110 fs respectively. For 532 nm and 6 ns pulses, dielectric breakdown occurs before NLA could occur due to high pulse influence. CLBO is found to show negative nonlinear refraction under high intensities. Hygroscopicity of CLBO is attributed to the entry of water through the channels that are present along a and b axes, which in turn, cause cracking. Doping, is expected to modify the size of the channels. Since certain dopants are found to improve the stability of CLBO, substitution of Cs site with Zn and Gd is carried out to reduce the size of channels. As there was no significant improvement with doping experiments, an alternate approach is attempted by coating with SiO2 thin films on the optical elements to prevent the water molecules from entering lattice through the channels. The results and discussion of the above studies are presented in the chapter 4. Lithium niobate is the most widely used single crystal for fabricating optical modulators, waveguides, SAW devices and optical parametric oscillators. Although single crystals of this ferroelectric material were grown way back in 1965 by Ball-man and Fedulov independently, most of the work till the beginning of 90’s was concentrated on crystals with congruent composition(CLN) because there were no suitable methods available for growing homogeneous single crystals of stoichiomet-ric lithium niobate(SLN). Recently, Double Crucible Czochralski method with au-tomatic powder feeding technique and top seeded solution growth technique with Li2O and K2O fluxes are shown to produce SLN crystals. In this work, top seeded solution growth technique with58.6 mol% Li2O composition(self flux) is adopted to grow SLN crystals and the details of the growth and investigations are presented in chapter 5. Initially, crystal growth of SLN, and Zn & Nd codoped SLN are de-scribed. The maximum dimesions of the SLN crystals are 20 mm diameter and 35 mm length. CLN crystals(30mm diameter and 70 mm length) are also grown for comparison. The growth rate for SLN crystals is approximately 25 times lower than that for CLN. The maximum amount of Zn added to the melt is 2.5 mol%. For Nd codoping, four concentrations (0.2, 0.5, 0.9, 1.5 mol%) have been chosen with Zn concentration in the melt fixed at 2.5 mol%. Addition of Zn is to enhance the pho-torefractive damage threshold and Nd to use SLN as laser host. Structural studies on the grown crystals using powder X-ray diffraction show no additional phases. The domain structure analysis by chemical etching studies reveal that it is sensitive to doping and temperature gradient above the melt surface. The grown crystals possess good transmission in the UV-Vis-NIR region. Apparent increase in the dielectric constant found in doped crystals is attributed to space charge effect. In Nd:Zn codoped SLN, the parameters corresponding to lasing (Judd-Ofelt parameters, radiative transition probabilities, branching ratios) have been evaluated and found to be better than those obtained for codoped CLN. Surface laser damage and photorefractive damage thresholds are enhanced by 2 and 4 orders of magnitude respectively for the crystals grown with 2.5 mol% Zn in the melt. Nonlinear absorption and refraction studies using femtosecond Z-scan experiments reveal a correlation between the nonstoichiometric defects and nonlinear absorption & refraction coefficients. Polarization switching studies carried out on pure and Zn doped samples indicate an enhancement in switching rate at elevated temperatures. In the sixth and final chapter, a comprehensive summary of the present work and the scope for further investigations related to this work are given.