Van der Waals epitaxy for high-quality flexible VO2 film on mica substrate

Vanadium dioxide (VO2) has wide application prospects in the electronics industry because of its rapid, reversible, and multi-stimulus response phase transition behavior. The development of flexible VO2 films and devices can further promote the development of flexible electronic materials and may play an important role in the next generation of wearable electronics. Here, we directly fabricated flexible VO2 films on mica via a pulsed-laser deposition system. By selection and optimization of the deposited condition, a high-quality flexible VO2 film with excellent metal to insulator (MI) transition properties of about a 3 order resistance variation in magnitude is successfully prepared. The growth competitions with different phases and different epitaxial orientations in the selection of deposited conditions verify the van der Waals (vdW) epitaxial growth mechanism of VO2 films on mica substrates. The invariable sheet resistance of VO2 films under different bending radii and bending cycles indicate their excellent mechanical flexibility and bending stability. Moreover, benefiting from the vdW epitaxy, a millimeter-scale, totally free-standing and transferable VO2 film is further obtained by a simple wet method and it is expected to be integrated into conventional silicon electronics and other systems. The high-quality, flexible, and peelable VO2 film prepared in our work lays a solid foundation for the application of VO2 films in wearable and integrated electronics.