Vanadium dioxide deposited by pulsed laser deposition: from materials optimization to applications in terahertz modulation
Date
2025
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Publisher
University of Delaware
Abstract
This dissertation discusses the synthesis, characterization, and application of phase transition materials, particularly vanadium dioxide (VO2), in dynamically tunable terahertz (THz) modulators. By leveraging pulsed laser deposition (PLD), this work demonstrates the fabrication of VO2 thin films with high quality, large-scale uniformity, and exceptional consistency, providing a foundation for THz modulation using phase transition materials. ☐ The dissertation begins by reviewing conventional THz modulation approaches, highlighting the advantages of utilizing phase transition materials and THz waves. Different methods of THz modulation and their advantages are discussed. The physical and electronic properties of VO2, including its insulator-to-metal transition, are explored, along with a comparison with other synthesis methods of phase change materials. ☐ A key part of this work is the optimized deposition of polycrystalline VO2 thin films using PLD. A comprehensive study on the VO2 deposition recipes and the quality of VO2 thin films are discussed. Characterization, including ellipsometry, resistance-temperature measurements, and terahertz time-domain spectroscopy (THz-TDS), confirms the high quality and reproducibility of the deposited VO2 thin films. ☐ The dissertation further presents the design, fabrication, and experimental results of a VO2-based THz beam steering metasurface. It achieves nearly 100% ordinary transmission in the "OFF" state and demonstrates broadband THz beam control. ☐ Furthermore, it introduces MEMS-actuated THz metamaterials, where the mechanical deformation of VO2 thin films serves as the actuator of a THz polarization modulator. The results reveal strong THz polarization modulation capabilities and enhanced tunability, which could be used in reconfigurable THz devices. ☐ In summary, the dissertation focuses on phase transition materials VO2 and THz modulation, providing new design concepts and operational mechanisms that can be further utilized in various devices and platforms. With optimized performance and capabilities, advanced optical applications, such as improved THz telecommunications, imaging, and sensing, could be realized.
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Keywords
Phase transition materials, Pulsed laser deposition, Vanadium dioxide, Terahertz modulation, Thin films