Direct measurement of compositional complexity-induced electronic inhomogeneity in VO2 thin films grown on gate dielectrics

We report on measurements of variation in metal-insulator transition characteristics through thickness in VO2 film grown on model SiO2 gate insulator by nanometric scale controlled etching followed by electrical and compositional measurements. The phase transition magnitude defined as ratio of resistivity at 25 degrees C to that at 100 degrees C of VO2 decreases from similar to 159 at the surface to similar to 14 at similar to 10 nm away from a VO2/SiO2 interface, showing a difference of > 10 times, while that for a VO2 thin film grown with identical conditions on single crystal sapphire only shows similar to 3 times difference. The off-stoichiometric composition near the VO2/SiO2 interface induced by unoriented growth on amorphous SiO2 is likely responsible for the dramatic change in transition characteristics. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3590920]