Twin-domain Epitaxial Growth and Metal-insulator Transition of VO 2 Thin Film on C-Plane Sapphire

We report heteroepitaxial growth of VO2 thin film onc-plane sapphire by pulsed DC magnetron sputtering. X-ray diffraction experiment indicates that the 150 nm thick film is in triple-domain (020)-epitaxial structure with six-fold rotational symmetry in the basal plane; in particular, off-axisΦ scans from (011) and (220) show twin and triple peaks in each group of the diffraction profiles due to angle β mismatch and V4+-V4+ dimerization, respectively. The epitaxial relationship between VO2 andc-plane sapphire can be concluded as be VO2 [010] ∥ Al2O3 [0001] and , with the in-plane lattice mismatch of 2.66% (tensile) along $\left[ {\bar 202} \right]$ and the out-of-plane lattice mismatch of -2.19% (compressive). Temperature dependence of resistivity in van der Pauw method shows that the resistivity changes by ~5 orders of magnitude through the metal-insulator transition, and a narrow hysteresis window of ~3 K is obtained between cooling and heating cycles with respect to phase-transition temperatures at 347.1 and 350.1 K.