A variety of nanostructures of tin (IV) oxide (TO) are synthesized using two fabrication methods: a solution spin-coating method followed by post-annealing in an oxygen flow and a newly developed catalyst-assisted pulsed laser deposition (PLD) technique. The spin-coating method is used to fabricate granular TO films with monodisperse, stable, ultra-small nanocrystallites (4-5 nm in size), the size of which is found to increase exponentially with post-anneal above 500??C. These nanocrystalline films are conductive and highly transparent, and their bandgap shows broadening due to a high carrier concentration. Their resistivity behavior as a function of temperature in the 50-280 K range can be explained by a two-medium transport model, i.e. transport through the crystalline grains and across the grain boundaries, and through the charge-depletion layer, where a potential barrier is found for transport across the grain boundaries. Electronic transport in these films follows a 3D-variable range hopping model, which reveals an increase in the localization length of carriers with increasing the TAnneal above the onset of exponential growth at TAnneal= 500??C. By homogenously doping Eu3+ in these nanocrystalline films up to a high doping level of ~ 8%, optical luminescence and magnetic orderings can be introduced into these nanocrystalline TO films. Both characteristic Eu3+ emission and defect-related TO emissions are observed in the otherwise transparent TO films upon UV-excitation. In spite of the non-magnetic nature of Eu3+ ions, magnetic orderings appear in the highly doped TO films below 50 K upon the emergence of Eu2Sn2O7 phase. In the second part of this work, we employ a layer of gold nanoislands with controlled sizes (10-50 nm) as catalysts for pulsed laser deposition of TO nanostructures. Highly crystalline TO nanobricks, cuboid nanoparticles, nanowires and nanobelts are obtained for the first time through vapour-solid or vapour-liquid-solid (VLS) mechanisms. Of particular interest are the micron long one-dimensional (1D) nanowires and nanobelts, with the smallest square and rectangular cross-sections, respectively, ever reported. These single-crystalline nanostructures are obtained at relatively low temperatures of 600??C, for nanowires, and 500??C, for nanobelts, and their cross-sectional sizes can be easily controlled by the size of the gold nanoislands. The nanobelts are found to grow along the [100] and [101] axes, while the nanowires appear to grow along the [100] axis. The growth evolution of the nanobelts are also investigated in detail revealing their VLS growth mode and their single-crystalline structure throughout the growth, which opens the prospect of controlling their growth axis and consequently their side-surface planes by pinning the base to the substrate at the desired crystalline orientation. Together, the two fabrication methods developed in the present work offer facile approaches to growing two scientifically and technologically important classes of TO nanostructures, i.e., nanocrystalline film and 1D nanostructures. Thorough characterization of the resulted nanostructured materials using advanced microscopic, spectroscopic and other techniques, including Helium Ion Microscopy, has been provided. Modification of structure, morphology and physical properties of these functional nanostructured materials are also illustrated by controlling the growth parameters and by (Eu-)doping, which pave the way for introducing new properties for applications in chemical sensing, (opto)electronics and displays.

Applications of zinc oxide (ZnO) for optoelectronic devices, including light emitting diodes, semiconductor lasers, and solar cells have not yet been realized due to the lack of high-quality p-type ZnO. In the research presented herein, pulsed laser deposition is employed to grow Ag-doped ZnO thin films, which are characterized in an attempt to understand the ability of Ag to act as a p-type dopant. By correlating the effects of the substrate temperature, oxygen pressure, and laser energy on the electrical and microstructural properties of Ag-doped ZnO films grown on c-cut sapphire substrates, p-type conductivity is achieved under elevated substrate temperatures. Characteristic stacking fault features have been continuously observed by transmission electron microscopy in all of the p-type films. Photoluminescence studies on n-type and p-type Ag-doped ZnO thin films demonstrate the role of stacking faults in determining the conductivity of the films. Exciton emission attributed to basal plane stacking faults suggests that the acceptor impurities are localized nearby the stacking faults in the n-type films. The photoluminescence investigation provides a correlation between microstructural characteristics and electrical properties of Ag- doped ZnO thin films; a link that enables further understanding of the doping nature of Ag impurities in ZnO. Under optimized deposition conditions, various substrates are investigated as potential candidates for ZnO thin film growth, including r -cut sapphire, quartz, and amorphous glass. Electrical results indicated that despite narrow conditions for obtaining p-type conductivity at a given substrate temperature, flexibility in substrate choice enables improved electrical properties. In parallel, N+-ion implantation at elevated temperatures is explored as an alternative approach to achieve p-type ZnO. The ion implantation fluence and temperature have been optimized to achieve p-type conductivity. Transmission electron microscopy reveals that characteristic stacking fault features are present throughout the p-type films, however in n-type N-doped films high-density defect clusters are observed. These results suggest that the temperature under which ion implantation is performed plays a critical role in determining the amount of dynamic defect re- combination that can take place, as well as defect cluster formation processes. Ion implantation at elevated temperatures is shown to be an effective method to introduce increased concentrations of p-type N dopants while reducing the amount of stable post-implantation disorder. Finally, the fabrication and properties of p-type Ag-doped ZnO/n-type ZnO and p-type N-doped ZnO/n-type ZnO thin film junctions were reported. For the N-doped sample, a rectifying behavior was observed in the I-V curve, consistent with N-doped ZnO being p-type and forming a p-n junction. The turn-on voltage of the device was ∼2.3 V under forward bias. The Ag-doped samples did not result in rectifying behavior as a result of conversion of the p-type layer to n-type behavior under the n- type layer deposition conditions. The systematic studies in this dissertation provide possible routes to grow p-type Ag-doped ZnO films and in-situ thermal activation of N-implanted dopant ions, to overcome the growth temperature limits, and to push one step closer to the future integration of ZnO-based devices.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 199-216.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 18, 2008) Includes bibliographical references.

Thesis (Ph. D. in Chemical Engineering)--Vanderbilt University, Aug. 2008. / Title from title screen. Includes bibliographical references.

Thesis (M.Sc.-Res.)--University of Wollongong, 2007. / Typescript. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Mechanical Engineering. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: High Temperature Superconductors (HTS) exhibit exceptional electrical properties that make them attractive candidates for numerous electronic devices and applications. However, constructing working devices can be challenging due to fabrication difficulties of these brittle ceramics. This thesis investigates new methods to make the fabrication of high quality YBa2Cu3O7 (YBCO) thin films easier and compatible with more materials. We present the development of a universal add-on method that can be used in situ to improve the quality of superconducting thin films deposited by Pulsed Laser deposition (PLD). We investigate the in situ application of electric fields and voltage biasing to improve the thin film growth. Considering various electrode configurations, we have developed a final electrode design that is stable and produces reproducible results. By introducing an insulated high voltage (HV) electrode into the chamber during deposition, the quality of the deposited thin films can be modulated depending on the polarity of the voltage applied. Applying a positive voltage improves the film quality obtained. Applying a negative voltage degrades the superconducting properties of the films. A simple proof-of-concept HTS dual-mode microwave filter was designed, fabricated and tested. Only the filter produced using our novel PLD technique displayed the correct filtering action upon cooling to 77K. This is attributed to the thin films better superconducting properties due to our developed technique. / AFRIKAANSE OPSOMMING: Hoë Temperatuur Supergeleiers (HTS) vertoon aantreklike elektriese eienskappe wat hulle goeie kandidate maak vir verskeie elektroniese toepassings. Om werkende toestelle te ontwikkel kan 'n uitdaging wees, as gevolg van die vervaardigings probleme wat bestaan vir hierdie bros keramiek materiaal. Hierdie tesis ondersoek nuwe metodes om die vervaardiging van 'n hoë gehalte YBa2Cu3O7 (YBCO) dun films makliker en versoenbaar te maak met verskeie materiale. Ons toon die ontwikkeling van 'n algemene metode wat maklik bygevoeg kan word om in situ die gehalte van supergeleidende dun films, wat deur gepulseerde laser deponering (PLD) gedeponeer is, te verbeter. Ons ondersoek die in situ toepassing van elektriese velde en spannings om die dun film groei te verbeter. Verder oorweeg ons verskeie elektrode konfigurasies en ontwikkel 'n finale elektrode ontwerp wat stabiel is en herhaalbare resultate produseer. Die kwaliteit van die gedeponeerde dun films kan gemoduleer word deur die byvoeging van 'n geïsoleerde hoogspannings (HV) elektrode tydens deponering, afhangende van die polariteit van die aangelegde spanning. 'n Positiewe spanning verhoog die film kwaliteit, terwyl 'n negatiewe spanning die supergeleidende eienskappe van die films verlaag. 'n Eenvoudige HTS dubbele-modus mikrogolffilter is ontwerp, vervaardig en getoets, om as toepassings voorbeeld te dien. Slegs die filter wat geproduseer was met behulp van ons nuwe PLD tegniek, vertoon die beste filter oordrag by 77K. Dit word toegeskryf aan die beter supergeleidende eienskappe van die dun film, as gevolg van die toepassing van ons ontwikkelde tegniek.