| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 95 === Nanowires, nanotips, and nanobelts, became hot research field with uniqueness optical, electrical and mechanical properties recently. 1D nanostructure had attracted much attention on their special optical and electrical properties in the past, but there only seldom investigation mentions about magnetic behavior. My investigation will focus on cobalt doped gallium nitride nanowires with their structure influencing and magnetic nature. The research of semiconductor has already entered the process in nano scale, and we must begin to consider the carriers’ spin and their conductive properties in this small world. The investigation of diluted magnetic semiconductors has attracted the attention of a lot of relevant researchers, and was regarded as the key material combining electricity and magnetism in the future. Moreover one dimensional structure possesses functions of devices too, so one dimensional nanostructure can be efficiently applied in Spintronics and integrated circuit system.
In 2000, T. Dietl utilized theoretical simulation to be contrasted with the experimental, and he found the manganese doped gallium arsenide were identical, and derive other magnetic characteristics in its relevant semiconductor materials. In this study, gallium nitride nanowires were successfully grown on Silicon substrate using a simple resistive heated furnace, APCVD system, at room temperature. Then we used tandem accelerator to implant magnetic atoms. Finally, the sample will be annealed by the furnace for defect removing. From scanning electron microscopy (SEM), x-ray diffraction (XRD) spectra, high resolution electron microscope (HRTEM) measurement and energy dispersive X-ray spectroscopy (EDS), analysis revealed that single crystalline of cobalt doped gallium nitride nanowires. The scanning electron microscope (SEM) investigations on the gallium nitride (GaN) nanowires show a surface morphology, and we can clearly see the wires bended and surface damaged. X-ray diffraction (XRD) spectra show no secondary phase formation after ion implantation, and the lattice was extended and short ranged distorted. This phenomenon was predicted by stress in the nanowires. After thermal annealing, the structure shows recrystallization clearly in the XRD spectra. High resolution electron microscope (HRTEM) measurement and energy dispersive X-ray spectroscopy (EDS) show no clusters obviously and atomic analysis on the surface. Finally, we used superconducting quantum interference device (SQUID) for magnetic measurement, and saw a hysteretic curve at 300K. The result shows the cobalt doped gallium nitride nanowires with room temperature ferromagnetic properties.
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