A Reconfigurable Remotely Epitaxial VO₂ Electrical Heterostructure

Abstract

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. VO2 has been regarded as an archetypal phase transition building block with superior metal–insulator transition characteristics. However, the reconfigurable VO2-based heterostructure and the associated devices are rare due to the fundamental challenge in integrating high-quality VO2 in technologically important substrates. In this report, for the first time, we show the remote epitaxy of VO2 and the demonstration of a vertical diode device in a graphene/epitaxial VO2/single-crystalline BN/graphite structure with VO2 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 VO2 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 VO2 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 VO2 could modify the transport characteristics. The work suggests the feasibility of developing a single-crystalline VO2-based reconfigurable heterostructure with arbitrary substrates and sheds light on designing novel adaptive photonics and electrical devices and circuits.

Thru-Hole Epitaxy: Is Remote Epitaxy Really Remote?

“…The remote epitaxy proposed by earlier studies [1][2][3][4][5][6][7][8] was validated mainly by the surface potential distribution calculated over a space layer complying with that of a substrate. We discussed some questions raised from the previous calculations in Supplementary Note3.…”

“…[1][2][3] Several other studies have also demonstrated the facile detachment of a film taken as evidence of remote epitaxy. [4][5][6][7][8] Strictly speaking, however, the easy detachability may not necessarily originate from the 'remoteness' of the remote epitaxy, but simply indicates that the binding between the film and space layer/substrate is weaker than the adhesion of the film to a detacher such as a thermal release tape. In fact, the entire remoteness of the remote epitaxy across the interface has never been rigorously verified yet.…”

Heterogeneous integration of single-crystalline rutile nanomembranes with steep phase transition on silicon substrates

“…Furthermore, surfaces of the released and transferred TiO 2 NM are uniform and intact without any defective boundaries 31 . Figure 2d shows that the entire area of TiO 2 films with lateral dimension of millimeter-scale and nanometer thickness was fully released from the VO 2 /TiO 2 substrates after this etching process.…”

MOVPE Growth of GaN via Graphene Layers on GaN/Sapphire Templates

“…Furthermore, the monolayer graphene does not completely screen the electrostatic potential of the substrate, which enables the epilayer to follow the crystalline template of the substrate [ 10 , 11 ]. The remote epitaxy and graphene-mediated exfoliation have been demonstrated for several material systems, including III-N [ 8 , 9 , 11 , 12 ], III-V [ 10 ], II-VI [ 9 ], transition metal dichalcogenides [ 13 ], perovskites [ 14 ], and other complex oxides [ 15 ].…”