Pour réaliser des fonctions électroniques sur support souple, le transistor en couches minces (TFT) est indispensable. Cette thèse a pour objectif d’approfondir les connaissances sur ces dispositifs.L’état de l’art est synthétisé dans le chapitre 1. Cette partie présente tout d’abord les TFT et justifie l’utilisation de l’oxyde d’indium gallium zinc (IGZO). Ensuite les propriétés de cet oxyde semi-conducteur amorphe sont traitées ; et enfin le chapitre fait état des résultats obtenus avec des TFT en IGZO.Le chapitre 2 établie un lien entre les propriétés de l’IGZO et le dépôt par pulvérisation cathodique. L’étude des films a été réalisée par ellipsométrie spectroscopique. Celle-ci a mis en évidence des variations dans les propriétés optiques dues au temps de dépôt, à la concentration en oxygène et à la position sur le substrat. Ces résultats ont été comparés à des mesures de résistivité, pour comprendre plus précisément la cause de ces variations.Le chapitre 3 élabore un procédé complet permettant de réaliser des TFT sur support souple. Le choix des différents matériaux est discuté, et les différents outils de procédés sont adaptés afin de réaliser ces dispositifs. Les TFT obtenus sont caractérisés en fonction du temps de recuit et sous flexion. Ils ont atteint des mobilités 10 cm².V-1.s-1.Le chapitre 4 étudie le dépôt d’IGZO par impression jet d’encre. Une encre a été formulée et les différents paramètres d’impression ajustés. Afin de comparer les différentes techniques de dépôt, des TFT avec canal en IGZO imprimé ont été réalisé et les films imprimés ont été caractérisé par ellipsométrie spectroscopique. Ces dispositifs ont atteint des mobilités de 0,4 cm2.V-1.s-1. / In order to carry out electronics functions on flexible substrate, thin film transistor is essential. The aim of this thesis is to increase knowledge on this device.State of art of IGZO TFT is summarized in chapter 1. This part presents thin film transistor and justify the choice of IGZO as the semiconductor material. Then, properties of this amorphous oxide semiconductor are discussed. Finally, this chapter presents the results obtained in the literature for IGZO based thin film transistor.Chapter 2 establishes a link between IGZO properties and sputtering deposition. Films are studied by spectroscopic ellipsometry. Experiments show variations in optical properties due to deposition time, oxygen content and position on the wafer. Resistivity measurements are carried out to understand more deeply the causes of these variations.Chapter 3 develops a complete process to achieve TFT on flexible substrate. The choice of different materials and processes is discussed. The performances of the TFT are investigated versus the annealing time and characterized under mechanical stress. Mobility up to 10 cm2.V-1.s-1 can be achieved after an annealing at 300°C during 1h30. Mechanical stresses show a degradation of the transistor induced by cracks in the oxide layer.Chapter 4 focuses on IGZO's deposition by inkjet printing. An ink is formulated using metallic salts and a solvents mixture. The parameters of the printing system are also optimized. To compare the different techniques of deposition, printed IGZO TFTs are characterized and compared with the one fabricated with the standard PVD deposition technique. Mobility is relatively lower and equals 0.4 cm2.V-1.s-1.

Semiconductor nanostructures have attracted considerable research interest due to their unique physical and chemical properties at nanoscale which open new frontiers for applications in electronics and sensing. Zinc oxide nanostructures with a wide range of applications, especially in optoelectronic devices and bio sensing, have been the focus of research over the past few decades. However ZnO nanostructures have failed to penetrate the market as they were expected to, a few years ago. The two main reasons widely recognized as bottleneck for ZnO nanostructures are (1) Synthesis technique which is fast, economical, and environmentally benign which would allow the growth on arbitrary substrates and (2) Difficulty in producing stable p-type doping. The main objective of this research work is to address these two bottlenecks and find a solution that is inexpensive, environmentally benign and CMOS compatible. To achieve this, we developed a Sonochemical method to synthesize 1D ZnO Nanorods, core-shell nanorods, 2D nanowalls and nanoflakes on arbitrary substrates which is a rapid, inexpensive, CMOS compatible and environmentally benign method and allows us to grow ZnO nanostructures on any arbitrary substrate at ambient conditions while most other popular methods used are either very slow or involve extreme conditions such as high temperatures and low pressure. A stable, reproducible p-type doping in ZnO is one of the most sought out application in the field of optoelectronics. Here in this project, we doped ZnO nanostructures using sonochemical method to achieve a stable and reproducible doping in ZnO. We have fabricated a homogeneous ZnO radial p-n junction by growing a p-type shell around an n-type core in a controlled way using the sonochemical synthesis method to realize ZnO homogeneous core-shell radial p-n junction for UV detection. ZnO has a wide range of applications from sensing to energy harvesting. In this work, we demonstrate the successful fabrication of an electrochemical immunosensor using ZnO nanoflakes to detect Cortisol and compare their performance with that of ZnO nanorods. We have explored the use of ZnO nanorods in energy harvesting in the form of Dye Sensitized Solar Cells (DSSC) and Perovskite Solar Cells.

This thesis presents an investigation into the factors affecting the morphology of hybrid inorganic/organic photoactive layers used in photovoltaic cells. Although optimisation of the organic (polymer) phase has received substantial attention, research into the morphology of the inorganic phase (semiconducting nanocrystals) remains limited. It is believed that there is a strong link between the morphology of the final photoactive film and the quality of the initial nanocrystal dispersion. To this end, two nanocrystal systems were investigated; zinc oxide (ZnO) and lead sulphide (PbS). ZnO nanocrystals were synthesised and found to possess reproducible characteristics. It was determined that colloid stability was initially dependent upon the presence of acetate groups bound to the surface, which in turn required a small quantity of methanol to be present in the organic dispersant. It was also discovered that while methanol evaporated readily from the surface of the nanocrystals, another molecule, 1-propylamine (1-PA), did not. Further investigations showed that while methanol only weakly physisorbed to the surface of ZnO nanocrystals, 1-PA formed strong, dative covalent bonds with Zn2+, preventing evaporation despite a low boiling point. Subsequent investigations into the effects of different ligands upon colloid stability found that amine-based groups typically possessed superior stabilising capabilities compared to alcohol-based analogues. The characteristics of nanocrystal / polymer blends were also investigated. It was determined that the nanocrystal dispersion became unstable at higher concentrations of polymer due to depletion aggregation. Films of nanocrystal / polymer blends were cast from dispersions containing either alcohol or amine-based ligands, and it was observed that dispersions stabilised with 1-PA possessed smooth morphologies on the micrometer scale. Investigations at the nanometer scale, however, revealed aggregates large enough to favour recombination.The latter half of this thesis regards the characterisation of PbS nanocrystals and investigations into triggered aggregation. It was determined that while PbS nanocrystals possessed reproducible characteristics, the stabilising molecule, oleic acid (OA) was insulating. The effects of exchanging the OA groups for a shorter ligand, butylamine (BA) were investigated.Finally, PbS nanocrystals were treated with a bidentate ligand, 1,2-ethanedithiol (EDT) to induce triggered aggregation. It was observed that the system was highly sensitive to the concentration of EDT in dispersion, forming small, relatively dispersed aggregates at low [EDT], and micrometer-sized crystalline structures at high [EDT]. The characterisation and entrapment of these nanocrystal structures within semi-conducting polymer films is also discussed.

A fully automated Temperature Dependent Hall (TDH) measurement setup has been assembled for the purposes of this study. This TDH setup is capable of measuring samples in the 20 K to 370 K temperature range. Sample sizes of up to 20 mm × 20 mm can be accommodated by the custom designed and manufactured sample holder. Samples with a resistance in the 1Ω to 250 MΩ range can be measured with this setup provided that the mobility of the sample is greater than 1 cm²/Vs. The computer program controlling the automated measurement processwas written in LabView™ version 6.1. Single crystal Zinc Oxide (ZnO) was the material under investigation in this study. Bulk ZnO samples grown by three different methods, namely pressurized melt growth, seeded chemical vapor transport (SCVT) growth and hydrothermal growth, were measured in the 20 K to 370 K range. The effect of annealing in argon atmosphere in the 550 ºC to 930 ºC range was investigated on all three ZnO types. In addition, hydrogen-implanted layers on semi-insulating hydrothermally grown ZnO were studied. These samples were annealed in the 200 ºC to 400 ºC range and Hall measurements in the 20 K to 330 K range were performed. Programs were written to fit, wherever possible, the obtained temperature dependent carrier concentration and mobility profiles to suitable theoretical models. The carrier concentration data was fitted to a multi-donor single acceptor charge balance equation for the purpose of extracting donor concentrations and activation energies. Before fitting, the data was corrected for the Hall scattering factor and, where necessary, for two-layer effects particularly a degenerate surface conduction channel that developed through annealing on the SCVT-grown and hydrothermally grown samples. The acceptor concentrations of the samples were obtained by fitting the mobility data to a model based on D.L. Rode’s method of solving the Boltzmann transport equation. Scattering mechanisms included in the model were piezoelectric and deformation potential acoustic modes, polar optic modes and ionized impurity scattering. It was found that the mobility data did not fit the model very well without assigning questionable values to other parameters, in this case the deformation potential. Plausible values for the acceptor concentration were however obtained. The carrier concentration data fitted the model well, but due to the large number of parameters to be extracted (up to six parameters in the case of three donors) there was often not much certainty in the extracted values This study shows that TDH analysis is a valuable tool to assess the quality of semiconductors. Bulk and degenerate surface (or interfacial) conduction are separated with relative ease, and shallow defect concentrations as well as compensation level concentrations could be extracted. The generally observed uncertainty in values obtained in the multi-parameter regression of carrier concentration data indicates that supplementary techniques such as photoluminescence are needed to support results obtained by the TDH technique. / Dissertation (MSc (Physics))--University of Pretoria, 2007. / Physics / MSc / unrestricted

Recently, efforts have been made for self-powering the batteries and portable electronic devices by piezoelectric nanogenerators. The piezoelectric nanogenerators can work as a power source for nano-systems and also as an active sensor. The piezoelectric nanogenerator is a device that converts random mechanical energy into electrical energy by utilizing the semiconducting and piezoelectric properties. Also, the mechanical energy is always available in and around us for powering these nano devices. The aim of the present thesis work is to explore 1D and 2D ZnO nanostructures (nanorods and nanosheets) on metal alloy substrates for the development of piezoelectric nanogenerators in energy harvesting and sensors applications. Hydrothermal synthesis method was adopted for the growth of ZnO nanostructures. The nanogenerators were fabricated by using the optimized synthesis parameters and subsequently studied their performance for power generation and as an active speed sensor. These 1D and 2D nanostructures based nanogenerators have opened up a new window for the energy harvesting applications and sensors development. The thesis is divided into following six chapters. Chapter 1: This chapter gives a general introduction about energy harvesting devices such as nanogenerators, available energy sources, mechanical energy harvesting, ZnO material and the details on hydrothermal synthesis process. A brief literature survey on different applications of piezoelectric nanogenerators is also included. Chapter 2: A novel flexible metal alloy (Phynox) and its properties along with its applications are discussed in this chapter. Details on the synthesis of 1D ZnO nanorods on Phynox alloy substrate by hydrothermal method are presented. Further, the optimization of parameters such as growth temperature, seed layer annealing and substrate temperature effects on the synthesis of ZnO nanorods are discussed in detail. As-synthesized ZnO nanorods have been characterized using XRD, FE-SEM, TEM and XPS. Chapter 3: It reports on the fabrication of piezoelectric nanogenerator on Phynox alloy substrate as power generating device by harvesting the mechanical energy. Initially, the performance of the nanogenerator for power generation due to finger tip impacts was studied and subsequently its switching polarity test was also carried out. Output voltage measurements were carried out using the in-house developed experimental setup. Stability test was also carried out to see the robustness of the nanogenerator. Finally, the output voltage response of the nanogenerator was studied for its use as an active speed sensor. Chapter 4: Synthesis of Al doped 2D ZnO nanorsheets on Aluminum alloy (AA-6061) substrate by hydrothermal method is reported in this chapter. The optimized parameters such as growth temperature and growth time effects on the synthesis of ZnO nanosheets are discussed. As-synthesized ZnO nanosheets were characterized using XRD, FE-SEM, TEM and XPS. The Al doping in ZnO is confirmed by EDXS and XPS analysis. Chapter 5: Cost effective fabrication of Al doped 2D ZnO nanosheets based nanogenerator for direct current (DC) power generation is reported in this chapter. The performance of the nanogenerator for DC power generation due to finger tip impacts was studied and subsequently its switching polarity test was also carried out. Output voltage measurements were carried out using the in-house developed experimental setup. Stability test was also carried out to see the robustness of the nanogenerator. Finally, the DC output voltage response of the nanogenerator was studied for its use as an active speed sensor. Chapter 6: The first section summarizes the significant features of the work presented in this thesis. In the second section the scope for carrying out the further work is given.

Orientador: Luis Vicente de Andrade Scalvi / Resumo: Este trabalho visa apresentar o desenvolvimento e as principais conclusões referentes à combinação de heterojunções a base de GaAs com óxidos semicondutores, para aplicações em dispositivos optoeletrônicos. O texto foi dividido em duas partes principais, sendo a primeira parte voltada para a síntese e produção do SnO2, relacionada com a formação da heteroestrutura GaAs/SnO2; e a segunda parte é focada na produção dos ressonadores de onda acústicas de bulk,na ordem de GHz, a base de GaAs/ZnO. Na primeira parte, priorizou-se filmes de SnO2, que foram depositados por duas técnicas: sol-gel dip-coating e evaporação resistiva. Os filmes foram depositados sobre substratos de vidro soda-lime, e sobre substratos de GaAs, de quartzo e de a-SiO2. SnO2 foi também depositado sobre filme de GaAs depositado por sputtering. No caso da evaporação resistiva, a rota sol-gel é utilizada também para a preparação do pó que é utilizado como precursor para a evaporação resistiva de filmes de SnO2, combinando essas duas técnicas. Foram investigadas as propriedades ópticas e elétricas de filmes finos de SnO2 dopado com 1% de Er3+ e estruturas hibridas de GaAs/SnO2: Er3+. Entre os principais resultados, verificou-se: 1) espectros de luminescência diferentes do íon Er3+ ao se depositar SnO2 sobre substrato de vidro ou GaAs; 2) Microscopia eletrônica de varredura (MEV) e espectroscopia de energia dispersiva de raios-x (EDX) para filmes de SnO2, depositados por evaporação resistiva, atestaram uma relação... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work aims to present the development and the main conclusions obtained so far regarding the combination of GaAs-based heterojunctions with semiconductor oxides, for applications in optoelectronic devices. The text has been divided in two main parts, where the first one is related to the synthesis and production of SnO2, associated with the formation of the heterostructure GaAs/SnO2; and the second one if focused on the production of bulk acoustic wave resonators, with frequencies in GHz range, based on GaAs/ZnO. In the first part, attention was given to SnO2 films, deposited by two techniques: sol-gel dipcoating and resistive evaporation, on soda-lime glass substrates, and on GaAs, quartz and a-SiO2 substrates. SnO2 was also deposited on GaAs film deposited by sputtering. In the case of resistive evaporation, the sol-gel route is also used to prepare the powder which is used as a precursor for resistive evaporation of SnO2 films, then, by combining these two techniques. Optical and electrical properties of Er3+ -doped SnO2 thin films were investigated as well as the hybrid structure GaAs/SnO2 .Among the main results were: 1) different luminescence spectra of Er3+ ion when depositing SnO2 on glass or GaAs substrate; 2) scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) for SnO2 films deposited by resistive evaporation show a relationship of the thermal annealing temperature with the concentration of Er ions in the surface layers; 3) this con... (Complete abstract click electronic access below) / Doutor

This thesis deals with the study of growth of zinc oxide crystals from supersaturated solutions using a scanning electron microscope and XRD methods. The work is divided into a theoretical and an experimental part. The theoretical part analyses issues related to the principle of operation of electrochemical cells with an emphasis on Ni-Zn batteries and phenomena limiting the life and efficiency of Ni-Zn batteries with a focus on phenomena that affect precipitation processes of zinc oxide crystals. It also analyses and compares the appropriateness of the methods that have been used to study the growth of the prepared zinc oxide crystals. The experimental part describes the preparation of a supersaturated solution, the process of each analysis and its evaluation. The results of each method are compared with the theoretical assumptions and among themselves. The experimental part also contains a chapter dealing with the design of in situ X-ray diffraction analysis methods of the obtained zinc oxide crystals.

Cette thèse s’inscrit dans le cadre d’une cotutelle internationale entre l’Université de Bourgogne Franche-Comté en France et l’Université de Sherbrooke au Canada. Elle porte sur le développement d'un biocapteur miniature pour la détection et la quantification de bactéries dans des milieux liquides complexes. La bactérie visée est l’Escherichia coli (E. coli), régulièrement mise en cause dans des épidémies d'infections alimentaires, et parfois meurtrière.La géométrie du biocapteur consiste en une membrane en arséniure de gallium (GaAs) sur laquelle est déposé un film mince piézoélectrique d’oxyde de zinc (ZnO). L'apport du ZnO structuré en couche mince constitue un réel atout pour atteindre de meilleures performances du transducteur piézoélectrique et consécutivement une meilleure sensibilité de détection. Une paire d'électrodes déposée sur le film de ZnO permet de générer sous une tension sinusoïdale une onde acoustique se propageant dans le GaAs, à une fréquence donnée. La face arrière de la membrane, quant à elle, est fonctionnalisée avec une monocouche auto-assemblée (SAM) d'alkanethiols et des anticorps anti-E. coli, conférant la spécificité de la détection. Ainsi, le biocapteur bénéficie à la fois des technologies de microfabrication et de bio-fonctionnalisation du GaAs, déjà validées au sein de l’équipe de recherche, et des propriétés piézoélectriques prometteuses du ZnO, afin d’atteindre potentiellement une détection hautement sensible et spécifique de la bactérie d’intérêt. Le défi consiste à pouvoir détecter et quantifier cette bactérie à de très faibles concentrations dans un échantillon liquide et/ou biologique complexe.Les travaux de recherche ont en partie porté sur les dépôts et caractérisations de couches minces piézoélectriques de ZnO sur des substrats de GaAs. L’effet de l’orientation cristalline du GaAs ainsi que l’utilisation d’une couche intermédiaire de Platine entre le ZnO et le GaAs ont été étudiés par différentes techniques de caractérisation structurale (diffraction des rayons X, spectroscopie Raman, spectrométrie de masse à ionisation secondaire), topographique (microscopie à force atomique), optique (ellipsométrie) et électrique. Après la réalisation des contacts électriques, la membrane en GaAs a été usinée par gravure humide. Une fois fabriqué, le transducteur a été testé en air et en milieu liquide par des mesures électriques, afin de déterminer les fréquences de résonance pour les modes de cisaillement d’épaisseur. Un protocole de bio-fonctionnalisation de surface, validé au sein du laboratoire, a été appliqué à la face arrière du biocapteur pour l’ancrage des SAMs et des anticorps, tout en protégeant la face avant. De plus, les conditions de greffage d’anticorps en termes de concentration utilisée, pH et durée d’incubation, ont été étudiées, afin d’optimiser la capture de bactérie. Par ailleurs, l’impact du pH et de la conductivité de l’échantillon à tester sur la réponse du biocapteur a été déterminé. Les performances du biocapteur ont été évaluées par des tests de détection de la bactérie cible, E. coli, tout en corrélant les mesures électriques avec celles de fluorescence. Des tests de détection ont été réalisés en variant la concentration d’E. coli dans des milieux de complexité croissante. Différents types de contrôles ont été réalisés pour valider les critères de spécificité. En raison de sa petite taille, de son faible coût de fabrication et de sa réponse rapide, le biocapteur proposé pourrait être potentiellement utilisé dans les laboratoires de diagnostic clinique pour la détection d’E. coli. / This thesis was conducted in the frame of an international collaboration between Université de Bourgogne Franche-Comté in France and Université de Sherbrooke in Canada. It addresses the development of a miniaturized biosensor for the detection and quantification of bacteria in complex liquid media. The targeted bacteria is Escherichia coli (E. coli), regularly implicated in outbreaks of foodborne infections, and sometimes fatal.The adopted geometry of the biosensor consists of a gallium arsenide (GaAs) membrane with a thin layer of piezoelectric zinc oxide (ZnO) on its front side. The contribution of ZnO structured in a thin film is a real asset to achieve better performances of the piezoelectric transducer and consecutively a better sensitivity of detection. A pair of electrodes deposited on the ZnO film allows the generation of an acoustic wave propagating in GaAs under a sinusoidal voltage, at a given frequency. The backside of the membrane is functionalized with a self-assembled monolayer (SAM) of alkanethiols and antibodies anti-E. coli, providing the specificity of detection. Thus, the biosensor benefits from the microfabrication and bio-functionalization technologies of GaAs, validated within the research team, and the promising piezoelectric properties of ZnO, to potentially achieve a highly sensitive and specific detection of the bacteria of interest. The challenge is to be able to detect and quantify these bacteria at very low concentrations in a complex liquid and/or biological sample.The research work partly focused on the deposition and characterization of piezoelectric ZnO thin films on GaAs substrates. The effect of the crystalline orientation of GaAs and the use of a titanium / platinum buffer layer between ZnO and GaAs were studied using different structural (X-ray diffraction, Raman spectroscopy, secondary ionization mass spectrometry), topographic (atomic force microscopy), optical (ellipsometry) and electrical characterizations. After the realization of the electrical contacts on top of the ZnO film, the GaAs membrane was micromachined using chemical wet etching. Once fabricated, the transducer was tested in air and liquid medium by electrical measurements, in order to determine the resonance frequencies for thickness shear mode. A protocol for surface bio-functionalization, validated in the laboratory, was applied to the back of the biosensor for anchoring SAMs and antibodies, while protecting the top side. Furthermore, different conditions of antibody grafting such as the concentration, pH and incubation time, were tested to optimize the immunocapture of bacteria. In addition, the impact of the pH and the conductivity of the solution to be tested on the response of the biosensor has been determined. The performances of the biosensor were evaluated by detection tests of the targeted bacteria, E. coli, while correlating electrical measurements with fluorescence microscopy. Detection tests were completed by varying the concentration of E. coli in environments of increasing complexity. Various types of controls were performed to validate the specificity criteria. Thanks to its small size, low cost of fabrication and rapid response, the proposed biosensor has the potential of being applied in clinical diagnostic laboratories for the detection of E. coli.

Transparent conductive oxides (TCOs) are key functional materials in existing and future electro-optical devices in the fields of energy efficiency, energy generation and information technology. The main application of TCOs is as thin films transparent electrodes where a combination of maximum electrical conductivity and transmittance in the visible to nearinfrared spectral range is required. However, due to the interdependence of the optical properties and the free electron density and mobility, respectively, these requirements cannot be achieved simultaneously in degenerately doped wide band-gap oxide semiconductors. Therefore, a detailed understanding of the mechanisms governing the generation of free charge carriers by extrinsic doping and the charge transport in these materials is essential for further development of high performance TCOs and corresponding deposition methods. The present work is aimed at a comprehensive investigation of the electrical, optical and structural properties as well as the elemental composition of (Al,Ga) doped ZnO and Nb doped TiO2 thin films prepared by pulsed DC reactive magnetron sputtering. The evolution of the film properties is studied in dependence of various deposition parameters through a combination of characterization techniques including Hall-effect, spectroscopic ellipsometry, spectral photometry, X-ray diffraction, X-ray near edge absorption, Rutherford backscattering spectrometry and particle induced X-ray emission. This approach resulted in the development of an alternative process control method based on the material specific current-voltage pressure characteristics of the reactive magnetron discharge which allows to precisely control the oxygen deficiency of the sputter deposited films. Based on the experimental data, models have been established that describe the room temperature charge transport properties and the dielectric function of the obtained ZnO and TiO2 based transparent conductors. On the one hand, these findings allow the prediction of material specific electron mobility limits by identifying the dominating charge carrier scattering mechanisms. On the other hand, new insight is gained into the origin of the observed transition from highly conductive to electrically insulating ZnO layers upon the incorporation of increasing concentrations of Al at elevated growth temperatures. Moreover, the Al and Ga dopant activation in ZnO have been quantified systematically for a wide range of Al concentrations and deposition conditions. A direct comparison of the Ga and Al doping efficiency demonstrates that Ga is a more efficient electron donor in ZnO. Further, it has been shown that high free electron mobilities in polycrystalline and epitaxial Nb:TiO2 layers can be achieved by reactive magnetron sputtering of TiNb alloy targets. The suppression of rutile phase formation and the control of the Nb dopant activation by fine tuning the oxygen deficiency have been identified as crucial for the growth of high quality TiO2 based TCO layers.

The commercial breakthrough of ZnO-based devices is hampered mainly by the unipolar n-type conductivity of this material. Hydrogen, which is known to form both electrically active and inactive complexes in ZnO, is considered as a main cause of this behavior. However, the existing literature is incomplete and partly contradictory. The object of the present thesis is a comprehensive investigation of the properties of two hydrogen-induced shallow donors HBC and HO, the hydrogen molecule H2, and a hydrogen-related defect, which gives rise to local vibrational modes (LVMs) at 3303 and 3320 cm-1, in ZnO and their interaction. The defects are characterized by Raman spectroscopy, infrared absorption spectroscopy, photoconductivtity (PC) and photoluminescence measurements. Based on the PC technique, a novel and highly sensitive spectroscopic approach is established, which is applicable for probing LVMs in strongly absorbing spectral regions. This technique enables the detection of the local modes of HO at 742 and 792 cm-1 in the neutral charge state. In consequence, earlier theoretical predictions regarding the microscopic structure of this shallow donor can be verified. In Raman measurements the electronic 1s→2s transition of HO is identified at 273 cm-1. This quantity is found to blue-shift with the HO defect concentration. A similar blue-shift of the 1s→2s(2p) donor transition of HBC is assigned to local lattice strain which was generated during high temperature processes. A Raman study of the H2 molecule covers its formation, stability, lattice position and interplay with the ZnO host. In particular, the role of H2 for the continuous generation of HO and HBC and the related n-type behavior is elaborated. The analysis unambiguously confirms that the so-called “hidden hydrogen” species is indeed H2. Moreover, the observation of the ortho-para-conversion process and the coupling to the host phonons contribute to a general understanding of H2 in semiconductors. Experimental results of the LVMs of 3303 and 3320 cm-1 in conjunction with model calculations yield an underlying defect containing three hydrogen atoms. This complex Y–H3 exhibits two configurations, which differ only in the orientation of one chemical bond. The findings are consistent equally with a zinc vacancy decorated with three hydrogen atoms and an ammonia molecule, respectively. Earlier models proposed in the literature are discarded. Measurements of concentration profiles by using Raman spectroscopy reveal the local distribution of the hydrogen-related defects as well as lattice imperfections. At the surface, where oxygen vacancies are present, HO is identified as the dominant shallow donor. Below, in parts of the crystal with low damage, HBC is the prevalent defect. In the sample center, characterized by a significant amount of zinc vacancies, the concentrations of H2 and Y–H3 show their maxima. By recording concentration profiles after thermal treatments a spatially resolved investigation of the interplay of these hydrogen-related defects is possible. / Der kommerzielle Durchbruch von ZnO-basierten Bauelementen ist hauptsächlich durch die beständige n-Typ Leitung des Materials eingeschränkt. Wasserstoff, der sowohl elektrisch aktive als auch inaktive Komplexe in ZnO formt, gilt als ein Hauptverursacher dieses Verhaltens. Jedoch ist die bestehende Literatur zu derartigen Defekten unvollständig, teils auch widersprüchlich. Gegenstand der vorliegenden Arbeit sind umfassende Untersuchungen der beiden wasserstoffinduzierten Donatoren HBC und HO, des Wasserstoffmoleküls H2 und eines Wasserstoffdefekts mit lokalen Schwingungsmoden (LSMn) bei 3303 und 3320 cm-1 in ZnO hinsichtlich ihrer Eigenschaften und gegenseitigen Wechselwirkung. Die Charakterisierung der Komplexe erfolgt mit Hilfe von Raman-Spektroskopie, Infrarot-Absorptionsspektroskopie, Photoleitfähigkeits- (PC) und Photolumineszenzmessungen. Basierend auf der PC Technik wird eine neuartige, hochsensitive Spektroskopiemethode etabliert, welche auch in stark absorbierenden Spektralbereichen anwendbar ist. Diese Technik ermöglicht erstmals die Detektion der LSMn von HO bei 742 und 792 cm-1 im neutralen Ladungszustand. Das experimentelle Ergebnis verifiziert theoretische Vorhersagen zur mikroskopischen Struktur dieses flachen Donators. In Raman-Messungen wird der elektrische 1s→2s Übergang von HO bei 273 cm-1 identifiziert und eine Blauverschiebung dieser Größe mit zunehmender HO-Konzentration beobachtet. Der Donator HBC zeigt ebenfalls eine Blauverschiebung des elektrischen 1s→2s(2p) Übergangs, welche durch lokale Gitterverzerrungen nach Hochtemperaturbehandlungen bedingt ist. Eine Raman-Studie charakterisiert das H2-Molekül in Bezug auf seine Bildung, Stabilität, Gitterposition und die Wechselwirkung mit dem ZnO-Kristall. Insbesondere wird seine Rolle für die fortwährende Bildung der Donatoren HO und HBC und des damit verbundenen n-Typ Verhaltens herausgearbeitet. Die Analyse ergibt die eindeutige Identifizierung der in der Literatur mit „hidden hydrogen“ bezeichneten Spezies als H2. Darüber hinaus tragen die beobachteten Umwandlungsprozesse zwischen ortho-H2 und para-H2 sowie die Kopplung an das Phononenspektrum zu einem generellen Verständnis von Wasserstoffmolekülen in Halbleitern bei. Die experimentellen Ergebnisse der LSMn bei 3303 und 3320 cm-1 in Kombination mit Modellrechnungen ergeben einen zugrundeliegenden Defekt mit drei Wasserstoffatomen. Dieser Komplex Y–H3 weist zwei Konfigurationen auf, welche sich durch die Orientierung von nur einer chemischen Bindung unterscheiden. Die Beobachtungen sind mit einer Zinkvakanz besetzt mit drei Wasserstoffatomen bzw. einem Ammoniakmolekül als mikroskopische Struktur gleichermaßen erklärbar. Bisherige Modelle aus der Literatur können damit widerlegt werden. Messungen von Konzentrationsprofilen mit Raman-Spektroskopie offenbaren die lokale Verteilung der Wasserstoffdefekte sowie von Gitterstörungen. An der Oberfläche, im Beisein von Sauerstoffvakanzen, ist HO der dominante flache Donator. In dem sich anschließenden ungestörten Kristallverbund ist hingegen der Donator HBC vorherrschend. In Zentrum, welches von Zinkvakanzen geprägt ist, sind die Konzentrationen von H2 und Y–H3 maximal. In Verbindung mit Temperaturbehandlungen ist eine räumlich aufgelöste Untersuchung der Wechselwirkung möglich.