Dative epitaxy of commensurate monocrystalline covalent-van der Waals moir\'e supercrystal

TL;DR

This paper introduces dative epitaxy, a new method for growing monocrystalline covalent 2D crystals on vdW substrates, combining the advantages of covalent and van der Waals epitaxy for improved control and quality.

Contribution

It demonstrates the first example of covalent monocrystalline Cr5Te8 grown on WSe2 via dative epitaxy, establishing a new paradigm for thin film epitaxy.

Findings

Successful growth of monocrystalline Cr5Te8 on WSe2

Formation of a commensurate moire superlattice

Cr5Te8 crystals exhibit square magnetic hysteresis

Abstract

Realizing van der Waals (vdW) epitaxy in the 80s represents a breakthrough that circumvents the stringent lattice matching and processing compatibility requirements in conventional covalent heteroepitaxy. However, due to the weak vdW interactions, there is little control over film qualities by the substrate. Typically, discrete domains with a spread of misorientation angles are formed, limiting the applicability of vdW epitaxy. Here we report the epitaxial growth of monocrystalline, covalent Cr5Te8 2D crystals on monolayer vdW WSe2 by chemical vapor deposition, driven by interfacial dative bond formation. The lattice of Cr5Te8, with a lateral dimension of a few ten microns, is fully commensurate with that of WSe2 via 3 x 3 (Cr5Te8)-7 x 7 (WSe2) supercell matching, forming a single crystalline moire superlattice. Our work has established a conceptually distinct paradigm of thin film epitaxy termed dative epitaxy, which takes full advantage of covalent epitaxy with chemical bonding for fixing the atomic registry and crystal orientation, while circumventing its stringent lattice matching and processing compatibility requirements; conversely, it ensures the full flexibility of vdW epitaxy, while avoiding its poor orientation control. Cr5Te8 2D crystals grown by dative epitaxy exhibit square magnetic hysteresis, suggesting minimized interfacial defects that can serve as pinning sites.