Self-Pixelation Through Fracture in VO2 Thin Films

Vanadium dioxide (VO2) is an archetypal Mott material with a metal-insulator transition (MIT) at near room temperature. In thin films, this transition is affected by substrate-induced strain but as film thickness increases, the strain is gradually relaxed and the bulk properties are recovered. Epitaxial films of VO2 on (001)-oriented rutile titanium dioxide (TiO2) relax substrate strain by forming a network of fracture lines that crisscross the film along well-defined crystallographic directions. This work shows that the electronic properties associated with these lines result in a pattern that resembles a "street map" of fully strained metallic VO2 blocks separated by insulating VO2 stripes. Each block of VO2 is thus electronically self-insulated from its neighbors, and its MIT can be locally induced optically with a laser, or electronically via the tip of a scanning probe microscope so that the films behave functionally as self-patterned pixel arrays.