| Summary: | 碩士 === 國立交通大學 === 物理研究所 === 98 === The electrical conduction mechanisms in nanoscale ZnO materials are an important and noticeable topic all the time. In this thesis, we have studied natively doped and Ga-doped ZnO nanowires. By measuring the temperature behavior of resistivities from 300 K down to liquid-helium temperatures and the magnetoresistances in low magnetic fields, we address the electrical conduction mechanisms in these nanowires.
We performed four-probe measurements on a series of natively doped ZnO nanowires. We found that our nanowires fell very close to the metal-insulator transition. Saturation of resistivity at the very low temperature region was observed. We found no appearance of variable-range hopping conduction. Instead, the combined thermal activation and nearest-neighbor hopping mechanisms dominated the overall temperature behavior of electrical resistivities.
In addition, we have measured the quantum-interference magnetoresistances of Ga-doped ZnO nanowires. We found that our nanowires were three-dimensional with regard to the weak-localization effect. The electron dephasing lengths were extracted. We found that, at temperatures above a few degrees Kelvin, the electron-phonon scattering dominated the dephasing, while the electron-electron scattering was negligibly small.
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