The effects of vacuum annealing on the structure of VO2 thin films

Noncrystalline VOx thin films were deposited onto p-doped Si (100) substrates at 400 °C using magnetron sputtering. By vacuum annealing, we obtained polycrystalline VO2 thin films with two different structures under a variety of annealing conditions. With the annealing temperature increasing and the annealing time developing, structures of the films underwent the following transformation: amorphous structure→metastable VO2 (B)→VO2 (B) + VO2 (M). Vacuum annealing is useful of acquiring VO2 thin films with high surface quality, but too high annealing temperature (500 °C) and too long time (15 h) are harmful, which make the surface degenerate.