Current-induced electrical self-oscillations across out-of-plane threshold switches based on VO2 layers integrated in crossbars geometry
Résumé
Electrically activated metal-insulator transition (MIT) in vanadium dioxide (VO2) is widely studied
from both fundamental and practical points of view. It can give valuable insights on the currently
controversial phase transition mechanism in this material and, at the same time, allows the
development of original MIT-based electronic devices. Electrically triggered insulator-metal
transitions are demonstrated in novel out-of-plane, metal-oxide-metal type devices integrating a VO2
thin film, upon applying moderate threshold voltages. It is shown that the current-voltage
characteristics of such devices present clear negative differential resistance effects supporting the onset
of continuous, current-driven phase oscillations across the vanadium dioxide material. The frequencies
of these self-sustained oscillations are ranging from 90 to 300 kHz and they may be tuned by adjusting
the injected current. A phenomenological model of the device and its command circuit is developed,
and allows to extract the analytical expressions of the oscillation frequencies and to simulate the
electrical oscillatory phenomena developed across the VO2 material. Such out-of-plane devices may
further contribute to the general understanding of the driving mechanism in metal-insulator transition
materials and devices, a prerequisite to promising applications in high speed/high frequency networks
of oscillatory or resistive memories circuits.