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 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.
| Original language | English (US) |
|---|---|
| Article number | 155430 |
| Journal | Physical Review B |
| Volume | 99 |
| Issue number | 15 |
| DOIs | |
| State | Published - Apr 29 2019 |
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All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
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Full orientation control of epitaxial MoS2 on hBN assisted by substrate defects. / Zhang, Fu; Wang, Yuanxi; Erb, Chad; Wang, Ke; Moradifar, Parivash; Crespi, Vincent Henry; Alem, Nasim.
In: Physical Review B, Vol. 99, No. 15, 155430, 29.04.2019.Research output: Contribution to journal › Article
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 Henry
AU - Alem, Nasim
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
VL - 99
JO - Physical Review B
JF - Physical Review B
SN - 2469-9950
IS - 15
M1 - 155430
ER -