Nonclassical Nucleation of Hexagonal Boron Nitride Enables Independent Control of Nucleation and Growth Rate

Abstract

Growth of high-quality, large-scale hexagonal boron nitride (h-BN) monolayers requires either an extremely low nucleation density or the seamless coalescence of identically oriented nuclei. We report on the nucleation process of h-BN on Pt(110), a substrate on which large single-crystalline domains can be obtained. Nucleation was investigated by scanning tunneling microscopy and UV photoemission. Neither self-collimated growth nor step-induced grain orientation can explain the scarcity or absence of twin domains, which here is caused by an extremely low nucleation density primarily owing to nonclassical nucleation. Key to the unexpected single-domain growth on a template with different symmetry is the instability of the Pt(110) surface layer, which adapts to the h-BN structure at high temperatures in different ways depending on the size of the h-BN islands. The resulting nonclassical nucleation offers additional levers, which allow reconciling low nucleation density with high growth rates, while in classical nucleation, a low nucleation rate is invariably tied to low growth rate.