Optimization of conditions for growth of vanadium dioxide thin films on silicon by pulsed-laser deposition

We systematically examined the effects of the substrate temperature (T-S) and the oxygen pressure (P-O2) on the structural and optical properties polycrystalline VO2 films grown directly on Si(100) substrates by pulsed-laser deposition. A rutile-type VO2 phase was formed at a T-S >= 450 degrees C at P-O2 values ranging from 5 to 20 mTorr, whereas other structures of vanadium oxides were stabilized at lower temperatures or higher oxygen pressures. The surface roughness of the VO2 films significantly increased at growth temperatures of 550 degrees C or more due to agglomeration of VO2 on the surface of the silicon substrate. An apparent change in the refractive index across the metal-insulator transition (MIT) temperature was observed in VO2 films grown at a T-S of 450 degrees C or more. The difference in the refractive index at a wavelength of 1550 nm above and below the MIT temperature was influenced by both the T-S and P-O2, and was maximal for a VO2 film grown at 450 degrees C under 20 mTorr. Based on the results, we derived the P-O2 versus 1/T-S phase diagram for the films of vanadium oxides, which will provide a guide to optimizing the conditions for growth of VO2 films on silicon platforms. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.