  We have grown VO2 thin films by laser ablation for electronic device
applications. In obtaining the thin films of the pure VO2 phase, oxygen partial
pressure is a critical parameter because vanadium oxides have several phases
with the oxygen concentration. It is found that the pure VO2 films are
epitaxially grown on Al2O3 substrate in the narrow ranges of 55-60 mTorr in an
Ar+10% O2 ambient, and that the mixed phase films are synthesized when the
deposition pressure slightly deviates from the optimum pressure. The (100)
oriented VO2 films undergo an abrupt metal-insulator transition (MIT) with
resistance change of an order of 104 at 338K. In the films of mixed phases, the
small change of the resistance is observed at the same temperature. The
polycrystalline films grown on SiO2/Si substrate undergo a broaden MIT of the
resistance. Furthermore, the abrupt MIT and collective current motion appearing
in metal are observed when the electric field is applied to the film.
