Tuning the phase transitions of VO2 thin films on silicon substrates using ultrathin Al2O3 as buffer layers

High quality VO2 thin films have been fabricated on silicon substrates using magnetron sputtering by introducing Al2O3 thin films as a buffer. The ultrathin Al2O3 deposited by plasma-assisted atomic layer deposition leads to a greatly improved crystallinity and textures in VO2 films. Dramatic change in electrical resistivity (4 orders of magnitude) and a small thermal hysteresis loop (similar to 4 K) are obtained across the metal-insulator phase transition (MIT). Remarkably, by applying perpendicular voltage to a VO2/Al2O3 based metal/VO2/ semiconductor device, electrically driven MIT switching characteristics have been observed with a tiny tunneling leakage current of similar to 10 mu A. These results show that an electric field alone is sufficient to trigger the MIT, and the realization of VO2 based ultrafast electrical switching devices on a silicon substrate is possible.