Stress relaxation effect on transport properties of strained vanadium dioxide epitaxial thin films

A stress relaxation effect on the transport properties of strained vanadium dioxide epitaxial thin films grown on Ti O2 (001) single crystal was investigated. When varying the film thickness ranging from 10 to 30 nm, there were no significant changes on the crystal structures identified by x-ray diffraction, i.e., no observable stress relaxation effects. On the other hand, increasing the film thickness resulted in the drastic changes on the transport properties including emerging the multisteps of the metal-insulator transition and also increasing the resistivity. The discrepancy between the observed crystal structure and the transport properties was related to the presence of the nanoscale line cracks due to thermal stress. Thus controlling thermal stress relaxation rather than the stress due to the lattice mismatch is critical to investigate the intrinsic nature on the transport properties of strained vanadium dioxide epitaxial thin films.