First-principles study of the growth and diffusion of B and N atoms on the sapphire surface with h-BN as the buffer layer

Currently,the preparation of large-size and high-quality hexagonal boron nitride is still an urgent problem.In this study,we investigated the growth and diffusion of boron and nitrogen atoms on the sapphire/h-BN buffer layer by first-principles calculations based on density functional theory.The surface of the single buffer layer provides several metastable adsorption sites for free B and N atoms due to exothermic reaction.The adsorption sites at the ideal growth point for B atoms have the lowest adsorption energy,but the N atoms are easily trapped by the N atoms on the surface to form N-N bonds.With the increasing buffer layers,the adsorption process of free atoms on the surface changes from exothermic to endothermic.The diffusion rate of B atoms is much higher than that of the N atoms thus the B atoms play a major role in the formation of B-N bonds.The introduction of buffer layers can effectively shield the negative effect of sapphire on the formation of B-N bonds.This makes the crystal growth on the buffer layer tends to two-dimensional growth,beneficial to the uniform distribution of B and N atoms.These findings provide an effective reference for the h-BN growth.