Atomically Thin Hexagonal Boron Nitride Nanofilm for Cu Protection: The Importance of Film Perfection

Coatings are routinely applied to protect metallic surfaces, and polymer coatings have been conventionally used where the thickness is not a dramatic issue.[1] For the next generation of nanoelectronics, nanoscale coatings are needed to accommo-date the compact design. 2D materials that can be fabricated into atomically thin film as a coating over the substrate can be a great choice. Graphene has recently been considered for this purpose, since it is robust and flexible, and the hexagonal hon-eycomb structure can effectively block any species, including helium.[2] Mixed results, however, have been reported.[3-7] Good short-term anti-corrosion performance was observed,[3-5] but over time, accelerated Cu oxidation and corrosion in air were found in the presence of graphene compared to the bare Cu substrate.[8,9] This acceleration is likely due to the high con-ductivity that assists electron transfer in the two-component galvanic cell between Cu and graphene, facilitating oxygen reduction and Cu oxidation around the defects in the long run.