TY - JOUR
T1 - Full orientation control of epitaxial MoS2 on hBN assisted by substrate defects
AU - Zhang, Fu
AU - Wang, Yuanxi
AU - Erb, Chad
AU - Wang, Ke
AU - Moradifar, Parivash
AU - Crespi, Vincent H.
AU - Alem, Nasim
N1 - Funding Information:
F.Z. and N.A. acknowledge support from the National Science Foundation (NSF) under EFRI 2-DARE Grant No. 1433378. Y.W. and V.H.C. acknowledge the NSF Materials Innovation Platform Two-Dimensional Crystal Consortium under Grant No. DMR-1539916 and the Extreme Science and Engineering Discovery Environment (XSEDE) for the allocation of computational resources (TG-DMR170050) on the LSU superMIC cluster. We also gratefully acknowledge the Center for 2-Dimensional and Layered Materials (2DLM) at the Pennsylvania State University. P.M. and N.A. acknowledge support from MRSEC under NSF Grant No. DMR-1420620. The authors are grateful to Professor J. Redwing for use of the APCVD system.
Publisher Copyright:
©2019 American Physical Society.
PY - 2019/4/29
Y1 - 2019/4/29
N2 - 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 two-dimensional (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.
AB - 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 two-dimensional (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.
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U2 - 10.1103/PhysRevB.99.155430
DO - 10.1103/PhysRevB.99.155430
M3 - Article
AN - SCOPUS:85065477815
VL - 99
JO - Physical Review B-Condensed Matter
JF - Physical Review B-Condensed Matter
SN - 2469-9950
IS - 15
M1 - 155430
ER -