Origins of Moire Patterns in CVD-grown MoS2 Bilayer Structures at the Atomic Scales
J Wang and R Namburu and M Dubey and AM Dongare, SCIENTIFIC REPORTS, 8, 9439 (2018).
The chemical vapor deposition (CVD)-grown two-dimensional molybdenum disulfide (MoS2) structures comprise of flakes of few layers with different dimensions. The top layers are relatively smaller in size than the bottom layers, resulting in the formation of edges/steps across adjacent layers. The strain response of such few-layer terraced structures is therefore likely to be different from exfoliated few- layered structures with similar dimensions without any terraces. In this study, the strain response of CVD-grown few-layered MoS2 terraced structures is investigated at the atomic scales using classic molecular dynamics (MD) simulations. MD simulations suggest that the strain relaxation of CVD grown triangular terraced structures is observed in the vertical displacement of the atoms across the layers that results in the formation of Moire patterns. The Moire islands are observed to nucleate at the corners or edges of the few-layered structure and propagate inwards under both tensile and compressive strains. The nucleation of these islands is observed to happen at tensile strains of 2% and at compressive strains of similar to 2.5%. The vertical displacements of the atoms and the dimensions of the Moire islands predicted using the MD simulation are in excellent agreement with that observed experimentally.
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