Phase evolution and electrical resistance properties in vanadium dioxide nanobeams with mechanical deformation-induced strain gradients

Abstract

Understanding the effect of strain on the physical properties of vanadium dioxide (VO2) is crucial for its effective use in flexible devices exposed to various strains. Stress (or strain) applied to VO2 plays a critical role in modulating its electrical and optical properties. Herein, we investigate the structural and electronic responses of VO2 nanobeams to bending deformation using interfacial adhesion between the VO2 and substrate, which can provide a route for understanding the correlation between the structural inhomogeneity and electrical properties associated with the strain gradient. The temperature-dependent phase evolution associated with the strain gradient in the bent nanobeam is resolved by characteristic Raman shifts and synchrotron diffraction, combined with stress analyses using a finite element method. The electrical resistance change and electro-thermal simulations reveal that the strain gradient-induced multiple phases in the bent nanobeam result in a higher resistance in the insulating state region, a higher transition temperature, a much broader transition range, and a smaller Joule heating effect, compared to the straight nanobeam. Our results may provide insight into the impact of the strain gradient in correlated materials, and can enable the deliberate control of physical properties using the strain gradient in nanostructures for flexible device applications.