Electric-Field-Induced Multistep Resistance Switching in Planar VO2/c-Al2O3 Structure

The electric-field-induced resistance switching of vanadium dioxide (VO 2 ) films grown on c -Al 2 O 3 (001) substrates was studied in planar devices with two terminal electrodes. We demonstrated multistep resistance switching in a device with dimensions of 5/1500 µm (electrode gap/electrode length), while only a single-step resistance switching was observed in a device with dimensions of 10/10 µm. Each step in the multistep resistance switching occurred within 100 ns and exhibited a time-independent constant value. Optical microscope observations of a filamentary current path in a VO 2 layer imply that initial filamentary current path formation and its development are responsible for the multistep resistance switching. Temperature-controlled X-ray diffraction (XRD) measurements suggested the coexistence of regions with a variety of transition temperatures, which is considered to be closely related to the appearance of the multistep resistance switching. The multistep resistance switching in the VO 2 -based planar device is promising not only for functional electronic device applications but also as a fundamental research for switching mechanism in oxide materials.