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

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.