Control of melting using nanoscale coatings

This article summarizes previous work using density-functional simulations to investigate the effects of nanoscale surface coatings on the dynamics of semiconductor surfaces near their melting points. We demonstrate that a coating of GaAs only a single monolayer thick causes a dramatic reduction in the diffusive motion of the surface atoms of a Ge(110) crystal, and causes superheating of the bulk at temperatures well above the Ge melting point, on the 10 ps time scale. In direct contrast, a similar single-monolayer coating of Ge will induce melting of a GaAs(110) surface, even 300 K below the bulk GaAs melting point. Using these atomicscale simulations, we suggest that the Ge monolayer causes the GaAs(110) surface to melt through transient penetration into the bulk, initiating collective diffusive motion of the Ga and As atoms. This work has important implications for high-temperature materials design, while simultaneously uncovering the fundamental causes of the melting phase transition.