Hydrothermal method for doping of zinc oxide nanowires and fabrication of ultraviolet photodetectors

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2012
Afal, Ayşegül
Nanotechnology comprises of the understanding and control of materials and processes at the nanoscale. Among various nanostructured materials, semiconducting nanowires attract much interest for their novel physical properties and potential device applications. The unique properties of these nanowires are based on their high surface to volume ratio and quantum confinement effect. Zinc oxide, having a direct, wide bandgap and large exciton binding energy, is highly appealing for optoelectronic devices. Due to excellent optical and electrical properties, zinc oxide nanowires have been utilized to fabricate various devices such as solar cells, light emitting diodes, transistors and photodetectors. Furthermore, zinc oxide, in its natural state exhibits n-type conductivity. Addition of impurities often leads to remarkable changes in their electrical and optical properties, which open up new application areas. Among the many synthesis methods for zinc oxide nanowires, hydrothermal method is an attractive one due to its easy procedure, simple equipment and low temperature requirements. In this thesis, zinc oxide nanowires were grown and doped by hydrothermal method. Different metal dopants such as copper, silver and aluminum were used for this purpose. These metals were selected as dopants due to their effect on magnetic properties, p-type conduction and electrical conductivity of ZnO nanowires, respectively. Doped nanowires were fully characterized and the changes in their physical properties were investigated. In addition, hydrothermally synthesized pure and aluminum doped zinc oxide nanowires were used as the electrically active components in ultraviolet photodetectors. Silver nanowires were utilized as transparent electrodes. Optoelectronic properties of the detectors were examined. Effect of in-situ annealing and nanowire length was investigated. Short recovery time, around 4 seconds, with a decent on/off ratio of 2600 was obtained. This design provides a simple and cost effective approach for the fabrication of high performance ultraviolet photodetectors.

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Citation Formats
A. Afal, “Hydrothermal method for doping of zinc oxide nanowires and fabrication of ultraviolet photodetectors,” M.S. - Master of Science, Middle East Technical University, 2012.