Abstract
Vanadium dioxide (VO2) typically is a strongly correlated material that undergoes a characteristic metal-insulator phase transition at ~341 K. The phase transition is accompanied with notable changes in various properties, enabling the extensive and emerging applications of VO2-based devices, such as smart windows, Mott field-effect transistors, optical modulators, and thermal actuators. Despite these admiring advances, VO2 related studies yet suffer from poor control on the fabrication of high-quality VO2 materials; this is a challenging topic and very significant to numerous promising application requirements. This thesis mainly focuses on the controllable fabrication and property modulation of one-dimensional VO2 materials, e.g., micro-/nano-scale beams, as well as their advanced applications. Two typical reaction approaches are applied to produce VO2. Wherein, hydrothermal reactions are used to facilitate the scalable fabrication of VO2 nanocrystals for macro-scale devices, and chemical vapor deposition reactions are used to fabricate high-quality VO2 single crystals for the investigation about their phase transition properties. Notably, oxide-assisted growth strategies are applied to the controllable growth of VO2, where different oxides serve as seed crystals, dopants, or inhibitors in the reactions. The kinetics of the VO2 growth are thus facilely manipulated in the modified reaction systems, enabling various morphologies and properties of as-grown samples. Consequently, wafer-scale vertically grown VO2 nanowire arrays and super-aligned VO2 nanobeam films that can be used for high-performance insect-sized soft robots are successfully fabricated. Furthermore, the as-grown VO2 single crystals present spatially ordered domain evolution processes and unique phase transition properties, potential for novel device applications such as nanoscale thermometers and single-crystalline actuators with outstanding performance.
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