In situ studies on twinning and cracking proximal to insulator-metal transition in self-supported VO2/Si3N4 membranes

Abstract

Mechanisms leading to correlation between structural phase transitions in functional oxides and consequent insulator-metal transitions driven by band gap closure are an active area of research. In cases where large volume changes are present, structural stability considerations become important. Here, we present in situ studies of mechanical instability of VO2 grown on self-supported Si3N4 membranes spanning the structural phase transition boundary of vanadium dioxide. We observe film cracking across the phase transition, and the transition-induced cracks correlate with the symmetry change and the corresponding changes in the optical/electrical response arising from the insulator-metal transition. Transmission electron microscopy studies revealed twinned platelets proximal to crack regions. Interestingly, the membranes are mechanically stable until a large fraction of resistance change occurs across the phase transition. The ability to manipulate the stability and controlled rupture of self-supported membranes through temperature or other stimuli could be of interest to microelectromechanical systems and sensor devices.