Full orientation control of epitaxial MoS2 on hBN assisted by substrate defects

Abstract

Inversion asymmetry in two-dimensional materials grants them fascinating properties such as spin-coupled valley degrees of freedom and piezoelectricity, but at the cost of inversion domain boundaries if the epitaxy of the grown 2D layer -- on a polar substrate -- cannot adequately distinguish what are often near-degenerate 0° and 180° orientations. We employ first-principles calculations to identify a method to lift this near-degeneracy: the energetic distinction between eclipsed and staggered configurations during nucleation at a point defect in the substrate. For monolayer MoS2 grown on hexagonal boron nitride, the predicted defect complex can be more stable than common MoS2 point defects because it is both a donor-acceptor pair and a Frenkel pair shared between adjacent layers of a 2D heterostack. Orientation control is verified in experiments that achieve ~90% consistency in the orientation of as-grown triangular MoS2 flakes on hBN, as confirmed by aberration-corrected scanning/transmission electron microscopy. This defect-enhanced orientational epitaxy could provide a general mechanism to break the near-degeneracy of 0/180° orientations of polar 2D materials on polar substrates, overcoming a long-standing impediment to scalable synthesis of single-crystal 2D semiconductors.

Published version updated. SI included

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Cited by in corpus (7)

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• Pinhole-seeded lateral epitaxy and exfoliation of GaSb films on graphene-terminated surfaces
• Selective-area van der Waals epitaxy of h-BN/graphene heterostructures via He${}^{+}$ irradiation-induced defect-engineering in 2D substrates
• Dynamic Growth/Etching Model for the Synthesis of Two-Dimensional Transition Metal Dichalcogenides via Chemical Vapour Deposition
• Microscopic mechanism of van der Waals heteroepitaxy in the formation of MoS2/hBN vertical heterostructures
• Interstitially bridged van der Waals interface enabling stacking-fault-free, layer-by-layer epitaxy
• Photoluminescence efficiency of MBE-grown MoSe${}_2$ monolayers featuring sharp excitonic lines and diverse grain structures