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 (∼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. (paper)