Analysis of the piezoelectric and current transport properties of zinc oxide nanostructures grown on fiber

Sammanfattning: It seems that nowadays the world is becoming as a small village due to the advancement in communication devices technology. These devices are playing an important role in the wellbeing of our life as almost each and every person is utilizing at least one of these devices. These devices consume energy and with our increased use of technology, we are faced  with energy crises. Therefore, the research community is keen in trying to explore alternative resources. One possibility is to search for the alternative resources from our environment. The attempt in this thesis was to utilize the piezoelectric properties by harvesting electrical energy from nanostructures. By utilizing the piezoelectric property of some materials, mechanical energy can be harvested as electrical output. It is worth mention that the ambient mechanical energy is the most available source of energy around us. Hence it is of interest to utilize it to develop future smart devices having the self-powered property. In this connection various experimental and mathematical techniques have been utilized for achieving this target.In this thesis zinc oxide (ZnO) nanostructures grown on textile substrates were the material. The use of textile as substrate is quite unique property of the presented work. Since textile is an essential and fundamental component of our everyday lives, therefore the use of textile as substrate can pave the way for the fabrication of novel self-powered devices. As in comparison with conventional and expensive substrates textile is very economical, lightweight, highly flexible, recyclable, reproducible, disposable, wearable and washable.I started my research work by integrating ZnO nanorods based nanogenerator on conductive textile fiber for the analysis of piezoelectric properties of ZnO nanorods. The acceptance of my work among the research community encouraged me to continue with it in order to improve the performance of the fabricated device. It is well known that piezoelectricity is a linear electromechanical coupling of the material in which mechanical energy is converted into electrical energy. Therefore, the piezoelectric properties of ZnO nanorods were investigated with regard to different physical parameters. In the electromechanical phenomena the analysis of the direct and the converse piezoelectric effect is also critical if conductive textile is used as a substrate. Therefore analysis of the direct and the converse piezoelectric effect was performed for ZnO nanowires grown on conductive textile fiber by using the nanoindentation method.Since the morphology of ZnO nanostructures can have an influence on the piezoelectric properties, the energy harvesting properties of ZnO nanoflowers were investigated and the achieved results confirmed that morphology has a strong influence on the piezoelectric properties. In addition, since there is an interest to generate a direct current (DC) piezoelectricity, a Schottky junction fabricated to one side of the nanogenerator material is needed. Therefore, ZnO nanorods based Schottky diode (Cu/ZnO) on textile fabric was fabricated and investigated. Moreover, frequency dependence electrical characterization was performed for analysis of current-transport properties of another Schottky diode (Au/ZnO) for understanding the carrier flow at the interface of the metal-semiconductor. Nevertheless, the consistency and stability of the constructed devices (ZnO nanogenerators and Schottky diodes) need some additional work to overcome these problems to achieve commercial realization of these devices in the future.