Two-Dimensional Metal-Insulator Transition in Ultrathin VO2 Nanosheets via Remote van der Waals Epitaxy.

Vanadium dioxide (VO2) undergoes a rutile-to-monoclinic metal-insulator transition (MIT) at 340 K. Marked by abrupt resistivity changes of 104-105 Ω·cm, this property has long attracted interest for electronic applications. However, when VO2 is a few nanometers thick, substrate-induced strain destabilizes the MIT, which limits device performance. To overcome this, two-dimensional (2D) VO2 nanostructures grown with a remote distance from substrates can reveal intrinsic strain-free electrical behavior and enable high-performance MIT-based devices. We report the growth of few-nanometer-thick 2D VO2 via remote van der Waals epitaxy. Transmission electron microscopy confirmed the monoclinic (M1) crystal structure. Conductive atomic force microscopy (c-AFM) measurements demonstrated a complete onset of 2D MIT at 1.5 V, achieving an on/off ratio of nearly 104.