Study on the Failure Mechanism of Antioxidant on Copper Foils with Growing Hexagonal Boron Nitride Films

Abstract

Recently, hexagonal boron nitride (h-BN) films have been considered as an effective alternative material for preventing metal oxidation due to its electrical insulating properties and ultrathin thickness. However, there are some issues when using synthesized h-BN on metal protection, especially because its antioxidation performance will decrease after a period of time. To address this problem, the h-BN films were synthesized at commercial Cu foil by the chemical vapor deposition (CVD) method, and the failure mechanism is proposed by experimental and density functional theory (DFT) calculations. The results indicate that a twin boundary with 558-N/B structures would be formed when two different orientation domains meet, and the h-BN domains can seamlessly stitch together for the same orientations or h-BN domains located in the different adjacent single atomic layer. Next, the failure mechanism of the antioxidant is considered and the synthesized h-BN at the Cu foil was treated by thermal oxidation, and we found the generation of Cu₂O/CuO induced the decoupling phenomenon between h-BN and Cu. Further DFT calculations indicate that the presence of twin boundaries and point defects can also facilitate the diffusion of the O atom, and h-BN edges terminated with H can promote the diffusion of the O atom and the diffusion and decomposition of H₂O molecules more than Cu(111) passivated h-BN, which accelerates the oxidation of Cu foil, leading to the formation of Cu₂O/CuO. This process increases the distance between h-BN and Cu and decreases the amount of Bader transfer and orbital hybridization of B, N, and Cu atoms between h-BN and Cu foil, thereby reducing the coupling between h-BN and Cu foil. This study can provide experimental and theoretical explanations for the failure mechanism of h-BN films in protecting metals from oxidation.