Dresden 2020 – scientific programme
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DS: Fachverband Dünne Schichten
DS 16: 2D semiconductors and van der Waals heterostructures III (joint session HL/DS)
DS 16.11: Talk
Tuesday, March 17, 2020, 12:45–13:00, POT 81
Surface Ripplocations in van der Waals materials: Structural & Electronic Properties — •James McHugh1, Pavlos Mouratidis1, Kenny Jolley1, and Patrick Briddon2 — 1Dept. of Chemistry, Loughborough University — 2School of Engineering, Newcastle University
Ripplocations are a new class of defect, unique to layered solids, which are characterised by the accommodation of extra material at sharp, localised folds. Dislocations in three-dimensional materials arise from the balance of strain and disregistry. In contrast, anisotropic van der Waals materials may completely alleviate strain through out-of-plane buckling.
We have conducted first-principles and analytical investigation of the properties of surface ripplocations on van der Waals layers. Analytical expressions for the formation energy, height and width of ripplocations are derived and compared to ab-initio simulations, showing that surface ripplocations readily form epitaxially on van der Waals materials.
The accommodation of extra material across a ripple is considered in terms of a Frenkel-Kontorova model, where it is found that ripplocations exhibit a "double kink" structure owing to the interplay of curvature and disregistry across the defect. Additionally, it is found that ripplocations induce a reduction in the band gap of layered semiconductors, with PDOS simulations identifying this change with the transition metal atoms across the curved regions. In combination with their high mobility this suggests the possibility of using ripplocations as a defect engineering platform.