Understanding the Phase Transition Evolution Mechanism of Partially M2 Phased VO₂ Film by Hydrogen Incorporation

Studies on the hydrogen incorporated M1 phase of VO₂ film have been widely reported. However, there are few works on an M2 phase of VO₂. Recently, the M2 phase in VO₂ has received considerable attention due to the possibility of realizing a Mott transition field-effect transistor. By varying the postannealing environment, systematic variations of the M2 phase in (020)-oriented VO₂ films grown on Al₂O₃(0001) were observed. The M2 phase converted to the metallic M1 phase at first and then to the metallic rutile phase after hydrogen annealing (i.e., for H₂/N₂ mixture and H₂ environments). From the diffraction and spectroscopy measurements, the transition is attributed to suppressed electron interactions, not structural modification caused by hydrogen incorporation. Our results suggest the understanding of the phase transition process of the M2 phase by hydrogen incorporation and the possibility of realization of the M2 phased-based Mott transition field-effect transistor.