Chemical Etching of Screw Dislocated Transition Metal Dichalcogenides.

Abstract

Chemical etching can create novel structures inaccessible by growth and provide complementary understanding on the growth mechanisms of complex nanostructures. Screw dislocation-driven growth influences the layer stackings of transition metal dichalcogenides (MX₂) resulting in complex spiral morphologies. Herein, we experimentally and theoretically study the etching of screw dislocated WS₂ and WSe₂ nanostructures using H₂O₂ etchant. The kinetic Wulff constructions and Monte Carlo simulations establish the etching principles of single MX₂ layers. Atomic force microscopy characterization reveals diverse etching morphology evolution behaviors around the dislocation cores and along the exterior edges, including triangular, hexagonal, or truncated hexagonal holes and smooth or rough edges. These behaviors are influenced by the edge orientations, layer stackings, and the strain of screw dislocations. <i>Ab initio</i> calculation and kinetic Monte Carlo simulations support the experimental observations and provide further mechanistic insights. This knowledge can help one to understand more complex structures created by screw dislocations through etching.