Temperature and electric field induced metal-insulator transition in atomic layer deposited VO2 thin films.

Amorphous vanadium oxide (VO 2 ) films deposited by atomic layer deposition (ALD) were crystallized with an ex situ anneal at 660–670 °C for 1–2 h under a low oxygen pressure (10 −4 to 10 −5 Torr). Under these conditions the crystalline VO 2 phase was maintained, while formation of the V 2 O 5 phase was suppressed. Electrical transition from the insulator to the metallic phase was observed in the 37–60 °C range, with an R OFF /R ON ratio of up to about 750 and ΔT C ≅ 7–10 °C. Lateral electric field applied across two-terminal device structures induced a reversible phase change, with a room temperature transition field of about 25 kV/cm in the VO 2 sample processed with the 2 h long O 2 anneal. Both the width and slope of the field induced MIT I-V hysteresis were dependent upon the VO 2 crystalline quality. [ABSTRACT FROM AUTHOR]