Nanotechnology is a technology of the design and the applications of nanoscale materials with their fundamentally new properties and functions. Nanosensor devices based on nanomaterials provide very fast response, low-cost, long-life time, easy to use for unskilled users, and provide high-efficiency. 1-D ZnO nanostructures materials have great potential applications in various sensing applications. ZnO is a wide band gap (3.37 eV at room temperature) semiconductor materials having large exciton binding energy (60 meV) and excellent chemical stability, electrical, optical, piezoelectric and pyroelectric properties. By doping the transition metals (TM) into ZnO matrix, the properties of ZnO nanostructures can be tuned and its room  temperature ferromagnetic behavior can be enhanced, which provide the TM-doped ZnO nanostructures as promising candidate for optoelectronic, spintronics and high performance sensors based devices. The synthesis of ZnO and TM-doped ZnO nanostructures via the low temperature hydrothermal method is considered a promising technique due to low cost, environmental friendly, simple solution process, diverse 1-D ZnO nanostructures can be achieved, and large scale production on any type of substrate, and their properties can be controlled by the growth parameters. However, to synthesize 1-D ZnO and TM-doped ZnO nanostructures with controlled shape, structure and uniform size distribution on large area substrates with desirable properties, low cost and simple processes are of high interest and it is a big challenge at present. The main purpose of this dissertation aims to develop new techniques to synthesize 1-D ZnO and (Fe, Mn)-doped ZnO nanostructures via the hydrothermal method, to characterize and to enhance their functional properties for developing sensing devices such as biosensors for clinical diagnoses and environmental monitoring applications, piezoresistive sensors and UV photodetector. The first part of the dissertation deals with the hydrothermal synthesis of ZnO nanostructures with controlled shape, structure and uniform size distribution under different conditions and their structural characterization. The possible parameters affecting the growth which can alter the morphology, uniformity and properties of the ZnO nanostructures were investigated. Well-aligned ZnO nanorods have been fabricated for high sensitive piezoresistive sensor. The development of creatinine biosensor for clinical diagnoses purpose and the development of glucose biosensor for indirect determination of mercury ions for an inexpensive and unskilled users for environmental monitoring applications with highly sensitive, selective, stable, reproducible, interference resistant, and fast response time have been fabricated based on ZnO nanorods. The second part of the dissertation presents a new hydrothermal synthesis of (Fe, Mn)-doped-ZnO nanostructures under different preparation conditions, their properties characterization and the fabrication of piezoresistive sensors and UV photodetectors based devices were demonstrated. The solution preparation condition and growth parameters that influences on the morphology, structures and properties of the nanostructures were investigated. The fabrication of Mn-doped-ZnO NRs/PEDOT:PSS Schottky diodes used as high performance piezoresistive sensor and UV photodetector have been studied and Fe-doped ZnO NRs/FTO Schottky diode has also been fabricated for high performance of UV photodetector. Finally, a brief outlook into future challenges and relating new opportunities are presented in the last part of the dissertation.

Widespread use of organic light emitting diodes (OLEDs) in solid state lighting and display technologies require efficiency and lifetime improvements, as well as cost reductions, inclusive of the transparent conducting oxide (TCO). Indium tin oxide (ITO) is the standard TCO anode in OLEDs, but indium is expensive and the Earth's reserve of this element is limited. Zinc oxide (ZnO) and its variants such as aluminum-doped ZnO (AZO) exhibit comparable electrical conductivity and transmissivity to ITO, and are of interest for TCO applications. However, the workfunction of ZnO and AZO is smaller compared to ITO. The smaller workfunction of AZO results in a higher hole injection barrier at the anode/organic interface, and methods of tuning its workfunction are required. This dissertation tested the hypothesis that workfunction tuning of AZO films could be achieved by surface modification with electronegative oxygen and fluorine plasmas, or, via use of nanoscale transition metal oxide layers (MoOx, VOx and WOx). Extensive UPS, XPS and optical spectroscopy studies indicate that O2 and CFx plasma treatment results in an electronegative surface, surface charge redistribution, and a surface dipole moment which reinforces the original surface dipole leading to workfunction increases. Donor-like gap states associated with partially occupied d-bands due to non-stoichiometry determine the effective increased workfunction of the AZO/transition-metal oxide stacks. Reduced hole injection barriers were engineered by ensuring that the surface ad-layers were sufficiently thin to facilitate Fowler-Nordheim tunneling. Improved band alignments resulted in improved hole injection from the surface modified AZO anodes, as demonstrated by I-V characterization of hole only structures. Energy band alignments are proposed based on the aforementioned spectroscopies. Simple bilayer OLEDs employing the surface modified AZO anodes were fabricated and characterized to compare their performance with standard ITO. Anodes consisting of AZO with MoOx or VOx interfacial layers exhibited 50% and 71% improvement in power efficiency (PE) and external quantum efficiency (EQE), respectively, compared to ITO at a working voltage of 9 V. The efficiencies of dipole reinforced AZO (O2/CFx plasma treated) anodes were comparable to ITO. The improved performance of the surface modified AZO anodes compared to as-deposited AZO is ascribed to improved hole injection, improved charge balance, and improved radiative recombination kinetics. The results suggest that surface modified AZO anodes are a promising alternative to ITO, given the lower cost and Earth abundance of Al and Zn.

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With the recent development of in situ transmission electron microscopy (TEM) characterization techniques, the real time study of property-structure correlations in nanomaterials becomes possible. This dissertation reports the direct observations of deformation behavior of Al2O3-ZrO2-MgAl2O4 (AZM) bulk ceramic nanocomposites, strengthening mechanism of twins in YBa2Cu3O7-x (YBCO) thin film, work hardening event in nanocrystalline nickel and deformation of 2wt% Al doped ZnO (AZO) thin film with nanorod structures using the in situ TEM nanoindentation tool. The combined in situ movies with quantitative loading-unloading curves reveal the deformation mechanism of the above nanomaterial systems. At room temperature, in situ dynamic deformation studies show that the AZM nanocomposites undergo the deformation mainly through the grain-boundary sliding and rotation of small grains, i.e., ZrO2 grains, and some of the large grains, i.e., MgAl2O4 grains. We observed both plastic and elastic deformations in different sample regions in these multi-phase ceramic nanocomposites at room temperature. Both ex situ (conventional) and in situ nanoindentation were conducted to reveal the deformation of YBCO films from the directions perpendicular and parallel to the twin interfaces. Hardness measured perpendicular to twin interfaces is ~50% and 40% higher than that measured parallel to twin interfaces, by ex situ and in situ, respectively. By using an in situ nanoindentation tool inside TEM, dynamic work hardening event in nanocrystalline nickel was directly observed. During stain hardening stage, abundant Lomer-Cottrell (L-C) locks formed both within nanograins and against twin boundaries. Two major mechanisms were identified during interactions between L-C locks and twin boundaries. Quantitative nanoindentation experiments recorded during in situ experiments show an increase of yield strength from 1.64 to 2.29 GPa during multiple loading-unloading cycles. In situ TEM nanoindentation has been conducted to explore the size dependent deformation behavior of two different types (type I: ~ 0.51 of width/length ratio and type II: ~ 088 ratio) of AZO nanorods. During the indentation on type I nanord structure, annihilation of defects has been observed which is caused by limitation of the defect activities by relatively small size of the width. On the other hand, type II nanorod shows dislocation activities which enhanced the grain rotation under the external force applied on more isotropic direction through type II nanorod.

A new set of thermal neutron detectors has been developed as a near term 3He tube replacement. The zinc oxide scintillator is an ultrafast scintillator which can be doped to have performance equal to or superior to 3He tubes. Originally investigated in the early 1950s, this room temperature semiconductor has been evaluated as a thermal neutron scintillator. Zinc oxide can be doped with different nuclei to tune the band gap, improve optical clarity, and improve the thermal neutron detection efficiency. The effects of various dopant effects on the scintillation properties, materials properties, and crystal growth parameters have been analyzed. Two different growth modalities were investigated: bulk melt grown materials as well as thin film scintillators grown by metalorganic chemical vapor deposition (MOCVD). MOCVD has shown significant advantages including precise thickness control, high dopant incorporation, and epitaxial coatings of neutron target nuclei. Detector designs were modeled and simulated to design an improved thermal neutron detector using doped ZnO layers, conformal coatings and light collection improvements including Bragg reflectors and photonic crystal structures. The detectors have been tested for crystalline quality by XRD and FTIR spectroscopy, for scintillation efficiency by photo-luminescence spectroscopy, and for neutron detection efficiency by alpha and neutron radiation tests. Lastly, a novel method for improving light collection efficiency has been investigated, the creation of a photonic crystal scintillator. Here, the flow of optical light photons is controlled through an engineered structure created with the scintillator materials. This work has resulted in a novel radiation detection material for the near term replacement of 3He tubes with performance characteristics equal to or superior to that of 3He.

ZnO window layers for CIGS solar cells are grown with a DC sputtering technique instead of a conventional RF sputtering technique. Transparent window layers and buffer layers are sputtered from the Zn target in the presence of Oxygen. The window layer is doped with Aluminum in order to achieve high electrical conductivity and thermal stability. The effect of different sputtering parameters on the electrical and optical properties of the films is elaborately studied. Sets of annealing experiments are also performed. Combinations of different deposition parameters are examined to design the optimum fabrication conditions. We are able to deposit 85% transparent, Al doped ZnO films having 002-axis orientation and 4e-4 ohm-cm resistivity, which is successfully, used on CIGS solar cells. Resistivity of undoped ZnO buffer layers is varied form 10-2 ohm-cm to unmeasurable by varying the sputtering parameters. The performance of a reactively sputtered window layer and a buffer layer have matched the performance of the RF sputtered ZnO on CIGS solar cells. There has been considerable effort to eliminate Chemical Bath Deposition of the CdS buffer layer from CIS solar cell fabrication. The performance of an undoped DC sputtered ZnO layer is examined on Cd free CIGS solar cells. The ZnO buffer layer is directly sputtered on an underlying CIGS material. The performance of Cd free solar cells is highly susceptible to the presence of Oxygen in the sputtering ambient of the buffer layer deposition [6]. As Oxygen is a growth component in reactive sputtering, the growth mechanisms of the DC-sputtered buffer layer are studied to improve the understanding. The performance of all reactively sputtered ZnO devices matched the values reported in the literature and the results for DC sputtered ZnO on Cd-free solar cells were encouraging.

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Dans la perspective d’améliorer les cellules du futur, nous avons élaboré respectivement des couches minces de ZnO dopé Mo par la méthode spray pyrolyse et dopé Yb par sputtering. Quel que soit la technique utilisée, toutes ces couches sont polycristallines, transparentes avec des surfaces uniformes. De plus les mesures d’effet Hall montrent une conductivité de type n dans le cas des deux systèmes étudiés. Concernant les films minces de ZnO dopé Mo, les propriétés électriques restent potentiellement intéressantes pour des applications en photovoltaïque en tant que dopant additionnel en plus des terres rares. Quant aux films minces de ZnOYb, les résultats de mesures PL ont clairement mis en évidence un couplage optique entre ZnO et l’Yb avec l’observation d’un photon infrarouge pour un photon UV incident. Ceci suggère que le concept « down-shift » est susceptible d’être validé. / In view of improving the cells of the future, we have elaborated respectively doped ZnO thin films by Mo spray pyrolysis method and doped Yb by sputtering. Whatever the technique used all these layers are polycrystalline, transparent with smooth surfaces. In addition, the Hall effect measurements show an n-type conductivity in the case of two systems studied. On thin films of ZnO doped Mo, the electrical properties are potentially interesting for photovoltaic applications as additional dopant in addition to rare earths. As for thin films ZnOYb, PL measurement results have clearly demonstrated an optical coupling between ZnO and Yb with the observation of a photon infrared photon UV incident. This suggests that the concept of "down-shift" is likely to be validated.

Le travail de thèse implique l'étude de matériaux conducteurs transparents sans indium (TCM), composants essentiels de nombreux dispositifs optoélectroniques, utilisant le dépôt spatial de couches atomiques sous pression atmosphérique (AP-SALD). Cette nouvelle technique partage les avantages principaux de l'ALD classique, mais en plus permet le dépôt de couches minces de haute qualité sur de grandes surfaces avec un contrôle précis à l’échelle nanométrique. Ce travail est focalisé sur l'optimisation des propriétés électriques des films d'oxyde de zinc dopé à l'aluminium (ZnO: Al), l'un des oxydes conducteurs les plus étudiés (TCOs). L'influence de plusieurs paramètres expérimentaux sur les propriétés physiques des films a été étudié. Le mécanisme de transport des porteurs de charge au niveau des joints de grains a été identifié comme étant l'émission tunnel plutôt que l’émission thermoïonique dans le ZnO fortement dopé, grâce à un nouveau modèle que nous avons développé en utilisant la méthode de la matrice de transfert à fonction Airy (AFTMM). En résumé, la densité du piège à électrons aux joints de grains pour les échantillons de ZnO:Al (2,2 × 10^20 cm-3) préparés par AP-SALD a été estimée à environ 7,6 ×10^13 cm-2. Notre modèle montre que la diffusion par les joints de grains est le mécanisme de diffusion dominant dans nos films fabriqués par AP-SALD. Nous avons trouvé que le recuit assisté par UV (~ 200 ° C) sous vide était une méthode efficace pour réduire les pièges aux joints de grains, entraînant une amélioration de la mobilité de 1 cm2V-1s-1 à 24 cm2V-1s-1 pour ZnO et à 6 cm2V -1s-1 pour ZnO:Al. Nous avons également utilisé AP-SALD pour fabriquer des TCM performants, stables et flexibles basés sur un réseau de nanofils métalliques. Pour cela, nous avons développé des électrodes composites en revêtant des nanofils argent ou cuivre (AgNWs ou CuNWs) avec ZnO, Al2O3, ou ZnO: Al. Un revêtement très conforme d’une épaisseur de quelques dizaines de nanomètres déposé par la technique AP-SALD améliore considérablement les stabilités thermique et électrique du réseau AgNWs ou CuNWs. Les propriétés optoélectroniques élevées (résistance de surface 10 ohms/carré, transmittance ~ 90%) du composite AgNW / ZnO: Al les rendent très appropriés pour une application en tant que TCM, en particulier pour les dispositifs flexibles.Enfin, en tant que technique de dépôt versatile, AP-SALD est bien compatible avec la technologie des cellules solaires à hétérojonction de silicium (Si-HET) en termes de passivation d'interface. L'intégration de TCM ZnO: Al et AgNWs à la cellule Si-HET a également été explorée. / The thesis work involves the study of Indium-free Transparent Conductive Materials (TCMs), key components of many optoelectronic devices, using Atmospheric Pressure Spatial Atomic Layer Deposition (AP-SALD). This new approach shares the main advantages of conventional ALD but allows open-air, very fast deposition of high-quality nanometer-thick materials over large surfaces. We focused on the optimization of the electrical properties of Aluminum doped Zinc Oxide (ZnO:Al) films, one of the most studied Transparent Conductive Oxides (TCOs). The effect of several experimental parameters on the physical properties of the deposited films has been evaluated. The carrier transport mechanism at grain boundaries was identified to be tunneling rather than thermionic emission in highly doped ZnO, thanks to a new model we have developed using the Airy Function Transfer Matrix Method. Accordingly, the electron trap density at grain boundaries for ZnO:Al samples (2.2×1020 cm-3) prepared by AP-SALD was estimated to be about 7.6×1013 cm-2. Our model shows that grain boundary scattering is the dominant scattering mechanism in our films. We found that UV assisted annealing (~ 200 °C) under vacuum was an efficient method to reduce grain boundary traps, resulting in an improvement of mobility from 1 cm2V-1s-1 to 24 cm2V-1s-1 for ZnO and to 6 cm2V-1s-1 for ZnO:Al. We have also used AP-SALD to fabricate high-performance, stable and flexible TCMs based on metallic nanowire network. For that, we developed composite electrodes by coating silver/copper nanowires (AgNWs/CuNWs) with ZnO, Al2O3, or ZnO:Al. A thin conformal coating deposited by AP-SALD technique enhanced drastically the thermal/electrical stability of the AgNWs/CuNWs network. High optoelectronic properties (resistivity ~ 10-4 Ωcm, transmittance ~ 90 %) of the AgNW/ZnO:Al composite make them very appropriate for application as TCM, especially for flexible devices.Finally, as a soft deposition technique, AP-SALD is completely compatible to the Silicon heterojunction (Si-HET) solar cell technology in terms of interface passivation. The integration of ZnO:Al and AgNWs based TCMs to Si-HET cell has also been explored.

L’oxyde de zinc dopé de type n est un excellent candidat pour la réalisation de films transparents et isolants thermiques grâce à ses propriétés d’absorption et de réflexion limitées aux domaines UV et IR. La synthèse en milieu polyol de particules nanostructurées d’oxyde de zinc dopé par du gallium a été utilisée afin de maîtriser la morphologie des cristallites. Il a été démontré expérimentalement et théoriquement que le maximum d’efficacité d’absorption IR est atteint pour un taux de dopant de 2,6 % molaire. Des suspensions de haute transmission dans le visible et absorption infrarouge significative ont été obtenues par l’encapsulation des particules avec un matériau fluoré d’indice de réfraction intermédiaire entre l’oxyde et le milieu dispersant, ainsi que par l’optimisation de l’état de dispersion de suspensions colloïdales grâce à l’adsorption de thioalcanes en surface des cristallites de ZnO dopés. / Thanks to its absorption / reflexion properties limited to the UV and the IR range, n-doped zinc oxide is a promising candidate for the elaboration of transparent and insulating films in smart windows. Nanostructured particles of Ga-doped zinc oxide were elaborated by polyol process. Polyol process was used in order to control the size and the morphology of the particles. Both experimental and theoretical data show that a maximum of IR absorption efficiency is obtained for a doping rate of 2.6 molar percent. Colloidal suspensions with high transmission in the visible range combined with significant absorption of the near infrared range were obtained using two strategies. The first one is the encapsulation of the Ga-doped ZnO particles by a fluoride shells with an intermediate refractive index between ZnO and the dispersion medium. The second one is the optimization of the dispersion state of nano-colloidal suspensions thanks to the adsorption of thioalkanes on the Ga-doped ZnO crystallite surfaces.