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

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