| Summary: | 碩士 === 國立交通大學 === 材料科學與工程學系所 === 105 === This work aims at investigating the role played by charge carrier in relation to oxygen vacancy (Vo) in mediating the ferromagnetic order in Cu-doped ZnO nanoparticle(denoted Cu_ZnO). Synthesized by an environment-friendly anti-solvent method, Cu_ZnO exhibits localized ferromagnetic order at room temperature resulting from the broken symmetry spin (BSS) bound to dopant. We demonstrate an effective tuning of Cu_ZnO’s ferromagnetism by means of varying the carrier concentration (c.c.) via an Ar/O2-treated rapid thermal annealing process. Combining synchrotron-based spectroscopy and Mott-Schottky analyses, we found that the Ar-treatment could result in the rise of c.c. in Cu_ZnO with a simultaneous increase of the Vo concentration, while O2-treatment exerted an opposite effect on the evolution of c.c./Vo. Temperature-dependent magnetic phase characterizations revealed that both Ar-treated and O2-treated Cu_ZnO featured noticeable paramagnetism below room temperature, which signaled a lack of carrier mediation to form the ferromagnetic order. However, Ar-treated Cu_ZnO could yield a larger ferromagnetic moment as well as a higher sustainability to resist thermal fluctuation compared to O2-treated Cu_ZnO. By varying carrier concentration through Vo control, we hope to provide a better understanding to how to develop robust ferromagnetic order in wide-band-gap oxide materials in order to further advance semiconductor-based spintronics technology.
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