Electrochemically Prepared Polycrystalline Copper Surface for the Growth of Hexagonal Boron Nitride

The controlled and reproducible growth of hexagonal boron nitride (h-BN) by chemical vapor deposition on polycrystalline copper foil substrates remains a challenge as typical growth surfaces contain microscopic ridges (height ≈ 100 μm) arising from the foil manufacturing process. In this work, we report a method to prepare commercially cold-rolled polycrystalline copper substrates for greatly improved growth of h-BN by a combination of thermal annealing in a reducing environment and electrochemical polishing to create an excellent surface that enables control of BN nucleation sites. We report a root mean square roughness of ∼1.2 nm for the Cu substrate after electropolishing and a reduction of nucleation sites along with enlargement of h-BN crystals with this combined approach. We also assess the potential role of surface features that exist on the Cu surface as nucleation sites. The development of an electrochemical process to prepare two-dimensional (2D) material growth substrates and demonstration of greatly improved growth of 2D materials directly point to more pragmatic large scale processing of 2D materials since such techniques are already utilized in large scale industrial processing.