Tailoring of TiO2 film microstructure by pulsed-DC and RF magnetron co-sputtering

In current study unconventional method of TiO2 film deposition by co-sputtering from two symmetrically placed inclined pulsed-DC and RF powered magnetrons has been tested. The differences in crystallinity, crystal texture and surface morphology of the films deposited by single magnetron and two magnetron co-sputtering process were investigated. For most of the practical applications anatase phase TiO2 with high fraction of {001} facets is desired. However, it was demonstrated that at maximum nominal power without sample heating/calcination single pulsed-DC magnetron sputtering tends to form smooth amorphous TiO2 films. On the other hand, due to the higher energetics of physical vapour condensation under similar conditions single RF magnetron sputtering deposits relatively rough films with highly oriented crystalline rutile and anatase TiO2 phases (phase orientations (110) and (101) respectively). By introducing pulsed-DC and RF magnetron co-sputtering approach it was possible to tailor the nucleation and growth of TiO2 crystalline domains and to form purely anatase phase TiO2 films with relatively high fraction of photocatalyticaly the most active {001} facets. Main insights into the advantages of the two magnetron co-sputtering process as well as general guidelines on promotion of specific crystal phases with different crystallographic orientation are provided.