Large Single-Crystal Hexagonal Boron Nitride Monolayer Domains with Controlled Morphology and Straight Merging Boundaries

Hexagonal boron nitride monolayers with domain sizes up to 700 μm² and geometry from triangle to hexagon are fabricated through a refined control over the precursor and morphology of the copper substrate. Hydrogen etching is shown to tailor the h-BN monolayers precisely along the grain boundaries, providing their morphology over micrometer scale and a new avenue toward fabricating nanoribbons.