Fig. 1.

Nonvolatile resistive switching in Au/VO₂/Ge vertical devices. (A) Schematic illustration of the out-of-plane VO₂ device and the measurement setup. The Au and highly doped Ge are top and bottom electrodes, respectively. (B) Resistance as a function of temperature of 150-nm VO₂ film. (Inset) Low-temperature insulating VO₂ monoclinic phase (M1 VO₂) and high-temperature metallic VO₂ rutile phase (R VO₂). (C) Room-temperature I-V curve. (D) After electroforming, the R-T curve of the VO₂ device shows another metal-insulator transition behavior at low temperatures.