Characterization of structural dynamics of VO2 thin film on c-Al2O3 using in-air time-resolved x-ray diffraction

概要

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The lattice motion and displacement of atoms in the unit cell in vanadium dioxide (VO2) grown on c-Al2O3 were characterized by static and time-resolved x-ray diffraction (XRD) measurements. The monoclinic-tetragonal phase transition of the VO2 unit cell and the twist motion of vanadium atoms in the unit cell were observed. The time-resolved XRD measurements were performed in air using a tabletop high-repetition femtosecond laser. The results obtained from the time-resolved XRD measurements suggested that the unit cell of the low-temperature monoclinic VO2 transformed into the high-temperature tetragonal phase extremely rapidly (within 25 ps); however, the atoms in the unit cell fluctuated or vibrated about the center of the tetragonal coordinates, which abated within ∼100 ps. Thus, the time-resolved XRD measurements of the Bragg angle, intensity, and width of the diffraction lines simultaneously revealed the phase transition of VO2 and the atomic motion in the unit cell.