Tuning the phase transitions of VO₂thin films on silicon substrates using ultrathin Al₂O₃as buffer layers

Abstract

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 (~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 ~10 μA. 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.