Characterization of structural dynamics ofVO2thin film onc-Al2O3using in-air time-resolved x-ray diffraction

Abstract

The lattice motion and displacement of atoms in the unit cell in vanadium dioxide $({\text{VO}}_{2})$ grown on $c{\text{-Al}}_{2}{\text{O}}_{3}$ were characterized by static and time-resolved x-ray diffraction (XRD) measurements. The monoclinic-tetragonal phase transition of the ${\text{VO}}_{2}$ 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 ${\text{VO}}_{2}$ 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 $\ensuremath{\sim}100\text{ }\text{ps}$. Thus, the time-resolved XRD measurements of the Bragg angle, intensity, and width of the diffraction lines simultaneously revealed the phase transition of ${\text{VO}}_{2}$ and the atomic motion in the unit cell.