First-principles Study of Intrinsic hBN Island Nucleated During CVD Initial Growth on Cu(111)

The initial growth mechanisms of intrinsic hexagonal boron nitride (hBN) islands on Cu(111) terraces during chemical vapor deposition (CVD) are investigated using density functional theory calculations. Edge energies are calculated with high accuracy, and critical sizes for previously unexamined island shapes are predicted. The formation energies of small hBN islands are found to be strongly influenced by the curl effect. Through two-dimensional variation of the chemical potential, three of the most stable structures at the critical size—zigzag hexagonal, zigzag boron-edge triangular, and zigzag nitrogen-edge triangular—are identified. Generalization of these shapes enables the drawing of two types of phase diagrams, demonstrating a strong dependence of shape stability on the chemical potential. It is further revealed that maintaining the chemical potential near a specific value is essential for increasing the critical size. These results provide explanations for the experimentally observed hBN island shapes on Cu surfaces during CVD and propose chemical potential conditions for growing hBN films with superior single crystallinity.