Growth of large single-crystalline two-dimensional boron nitride hexagons on electropolished copper.

ABSTRACT

Hexagonal-boron nitride (h-BN) or "white graphene" has many outstanding properties including high thermal conductivity, high mechanical strength, chemical inertness, and high electrical resistance, which open up a wide range of applications such as thermal interface material, protective coatings, and dielectric in nanoelectronics that easily exceed the current advertised benefits pertaining to the graphene-based applications. The development of h-BN films using chemical vapor deposition (CVD) has thus far led into nucleation of triangular or asymmetric diamond shapes on different metallic surfaces. Additionally, the average size of the triangular domains has remained relatively small (∼ 0.5 µm(2)) leading to a large number of grain boundaries and defects. While the morphology of Cu surfaces for CVD-grown graphene may have impacts on the nucleation density, domain sizes, thickness, and uniformity, the effects of the decreased roughness of Cu surface to develop h-BN films are unknown. Here, we report the growth and characterization of novel large area h-BN hexagons using highly electropolished Cu substrate under atmospheric pressure CVD conditions. We found that the nucleation density of h-BN is significantly reduced while domain sizes increase. In this study, the largest hexagonal-shape h-BN domain observed is 35 µm(2), which is an order of magnitude larger than a typical triangular domain. As the domains coalesce to form a continuous film, the larger grain size offers a more pristine and smoother film with lesser grain boundaries induced defects.