Structure and Metal‐to‐Insulator Transition of VO2 Nanowires Grown on Sapphire Substrates

Single‐crystalline VO2 nanowires exhibit interesting growth phenomena along three equivalent <11̄ 00> directions of the C‐planes of the sapphire substrates. Under certain growth conditions, VO2 nanowires form V‐shaped twining structures with uniform morphologies and interfaces. Due to the strong elastic stress at the interfaces, the metal‐to‐insulator transition (MIT) of individual VO2 nanowires grown directly on sapphire substrates were observed to display distinct electrical hysteresis loops relative to VO2 nanowires dispersed on sapphire substrates. The distinctive characteristics in the hysteresis loops, exhibited in the process of MIT, are shown to be correlated with the nucleation and growth of periodic/random domain structures in the nanowires during the heating and cooling processes. The periodic domain structures observed in the directly grown nanowires can be explained under the framework of a modified stress‐induced elastic energy model that was first developed for ferroelectric systems.