Low-Dimensional ZrO₂　and HfO₂　Nanomaterials: Synthesis, Characterization And Properties

Owing to unique physical and chemical properties, nanostructured zirconium oxide and hafnium oxide have exhibited promising applications in electrics, optics, temperature-resistant and other fields. Preparing low-dimensional nanostructures by phycal and chemical methods and investigating their general formation mechanism may be a solution to the precise control of their structure, morphology and properties. In this dissertation, systematic explorations have been carried out on synsthetic strategies of zirconium oxide and hafnium oxide, their formation mechanisms and properties.A simple synthetic method for nanobelts has been developed. ZrO2and HfO2nanowires, nanobelts were prepared in homemade electrospinning setup. The effects of electrospinning parameters such as solution concentration, the voltage and the distance between the cathode and the anode, ambient temperature on the morphology of nanobelts were systematic investigated. We found that the aspect ratio of nanobelts could be adjusted by controlling the polymer solution concentration. In addition, elevated ambient temperature is favorable to the formation of the nanobelts and ultra-thin nanobelts (-5nm) could be obtained at70℃. On this basis, the growth mechanism of nanobelts was discussed. It was found that phase separation effect is the main factor in the formation process of nanobelts and the rapid evaporation of solvent played an important role. Several polymer solutions with different solvent have been electrospun and corresponding nanobelts were fabricated by this method. The potential application of rare-earth-doped HfO2nanobelts in the light emitting devices was explored.To enhance the intensity of luminescence in nanoparticles, rare earth doped ZrO2nanoparticles coated with inert and active shells have been synthesized. The effects of the shell thickness and rare earth doped active shell on the luminescence of the nanoparticles have been demonstrated. The active-shell serves two purposes:one is to protect the luminescing rare earth ions from the non-radiative decay and the other is to transfer UV absorbed radiation to the luminescing core.HfO2has emerged as the most promising high dielectric for MOS devices. In this dissertation, HfO2thin films were prepared by reactive sputtering at silicon substrate. The impact of the deposition parameters and post-treatment on the structure and electrical property of HfO2films was analysed to explore the best preparation condition of HfO2film. Moreover, the formation mechanism of various defects was indicated and the defects effect on the electrical properties of the films was suggested.