Formation of Porous Heterostructure Nanowires through Solid-state Diffusion Reaction

• Main Authors: Ho, Jo-Hsuan, 何若瑄
• Other Authors: Wu, Wen-Wei
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/57mucp

碩士 === 國立交通大學 === 材料科學與工程學系所 === 105 === Metal oxide materials have been widely investigated owing to their various and excellent physical and chemical properties. Among these transitional metal oxides, zinc oxide and iron oxide each play an important role in applications of photoelectric and magnetic. Zinc oxide is naturally a direct band-gap, n-type semiconductor which has wide band-gap. As a result, it exhibits significant physical properties in optical, electrical and piezoelectric fields. Iron is known for its magnetic properties, which possesses various oxidation states, including wüstite(FeO), hematite(α-Fe2O3), maghemite(γ-Fe2O3) and magnetite(Fe3O4). In this study, we observe the diffusion behaviors between zinc oxide nanowire and iron metal by in-situ transmission electron microscope. Zinc oxide nanowires and iron metal are annealed under ultra-high-vacuum condition. By solid-state diffusion reaction, the Fe3O4 and ZnO/Fe3O4 heterostructure nanowires were formed. The diffusion of iron atoms in zinc oxide lattice can be observed at 800 K annealed for 10 minutes. As-formed porous Fe3O4 nanowire with voids can be divided into two types by their appearances : disc-like void and zigzag-like void. Disc-like voids are more common than zigzag-like voids. By HRTEM images and FFT diffraction pattern analysis, we found that disc-like voids formed along the close-packing plane of Fe3O4. Moreover, there is an epitaxial relationship between Fe3O4 crystal with disc-like voids and ZnO crystal. We also compare two voids type Fe3O4/ZnO heterostructure nanowires on the same sample. It indicated that the diffusion rate of disc-like Fe3O4 nanowire is much slower since it needs more time and energy to adjust the lattice mismatch and form epitaxial interface.