A Reconfigurable Remotely Epitaxial VO Electrical Heterostructure.

The reconfigurability of the electrical heterostructure featured with external variables, such as temperature, voltage, and strain, enabled electronic/optical phase transition in functional layers has great potential for future photonics, computing, and adaptive circuits. VO has been regarded as an archetypal phase transition building block with superior metal-insulator transition characteristics. However, the reconfigurable VO-based heterostructure and the associated devices are rare due to the fundamental challenge in integrating high-quality VO in technologically important substrates. In this report, for the first time, we show the remote epitaxy of VO and the demonstration of a vertical diode device in a graphene/epitaxial VO/single-crystalline BN/graphite structure with VO as a reconfigurable phase-change material and hexagonal boron nitride (h-BN) as an insulating layer. By diffraction and electrical transport studies, we show that the remote epitaxial VO films exhibit higher structural and electrical quality than direct epitaxial ones. By high-resolution transmission electron microscopy and Cs-corrected scanning transmission electron microscopy, we show that a graphene buffered substrate leads to a less strained VO film than the bare substrate. In the reconfigurable diode, we find that the Fermi level change and spectral weight shift along with the metal-insulator transition of VO could modify the transport characteristics. The work suggests the feasibility of developing a single-crystalline VO-based reconfigurable heterostructure with arbitrary substrates and sheds light on designing novel adaptive photonics and electrical devices and circuits.