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 a 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, whereas 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 formation of an amorphous insulating VOx (x>2.6) phase coexisting with VO2 and the high vanadium vacancy concentration of the VO2. These phenomena are the result of the excess oxygen during the growth and the interaction between the silicon substrate and the growing film.