Effect of the substrate on the insulator-metal transition of vanadium dioxide films

Single-phase vanadium dioxide films grown on (0001) sapphire and (001) silicon substrates show very different insulator-metal electronic transition. A detailed description of the growth mechanisms and the substrate-film interaction is given, and the characteristics of the electronic transition are described by the morphology and grain boundary structure. (Tri-)epitaxy-stabilized columnar growth of VO2 takes place on the sapphire substrate, while on silicon the expected Zone II growth is identified. We have found that in the case of the Si substrate the reasons for the broader hysteresis and the lower switching amplitude are the higher average oxygen vacancy concentration and the VxSiyO built up in the grain boundaries. These phenomena are the result of the material transport between the silicon substrate and the growing film.