Vanadium oxide (VOx, x=0 similar to 2.5) films with several different structures were deposited using reactive unbalanced magnetron sputtering; a metallic vanadium target was used. Helium gas was introduced to the deposition process to cause Penning ionization, which was enhanced by the ’unbalanced’ magnetic field arrangement at the cathode. The transition region corresponding to the oxidation of a target surface was observed at the lower reactive gas (oxygen) partial pressure. A thermochromic film, rutile VO2, and its metastable phase, VO2(B), were successfully deposited at 400 degrees C by controlling the oxygen and helium partial pressures. The plasma diagnostics, examined by optical emission monitoring, revealed that the relative electron temperature was also increased by the Helium introduction, which should result in an increasing plasma potential close to the substrate surface and hence an increase in the ion-bombardment energy during the film growth.