Ripplocations = surface ripples + dislocations ?

Dislocations are topological line defects in three-dimensional crystals. Same-sign dislocations repel according to Frank’ s rule . This rule is broken for dislocations in van der Waals (vdW) layers, which possess crystallographic Burgers vector as ordinary dislocations but feature “ surface ripples”  due to the ease of bending and weak vdW adhesion of the atomic layers. We term these line defects “ ripplocations”  in accordance to their dual “ surface ripple”  and “ crystallographic dislocation” characters. Unlike conventional ripples on noncrystalline (vacuum, amorphous or fluid substrates, ripplocations tend to be very straight, narrow, and crystallographically oriented. The self-energy of surface ripplocations scales sublinearly with the magnitude of the Burger's vector , indicating that same-sign ripplocations attract and tend to merge, opposite to conventional dislocations. Using in situ transmission electron microscopy, we directly observed ripplocation generation and motion when few-layer MoS2 films were lithiated or mechanically processed. Being a new subclass of elementary defects, ripplocations are expected to be important in the processing and defect engineering of vdW layers.