Coarsening of polycrystalline patterns in atomically thin surface crystals

Abstract

Atomically thin phases that crystallize on the surfaces of liquids above their melting point represent an emerging class of 2D crystals. Using AuSi as a model system, we show that their formation results in polycrystalline patterns that, unlike current generation 2D crystals, naturally coarsen as they form. The dynamics of the low-dimensional grain boundaries and their junctions is strongly coupled to the supporting liquid. The reorientation necessary for curvature driven interfacial kinetics entails diffusional dissipation with the liquid via mobile antisite defects, leading to a scale-independent power law dependence of the coarsening rate. Our study highlights natural thermal evolution of these polycrystals as a viable pathway for engineering the grain boundary networks in 2D surface crystals, motivating the search for a broader set of stable 2D surface crystals in multicomponent liquids and amorphous solids.