Schottky barriers at hexagonal boron nitride/metal interfaces: A first-principles study

The formation of a Schottky barrier at the interface between a metal and hexagonal boron nitride $(h-\mathrm{BN})$ is studied using density functional theory. For metals whose work functions range from 4.2 to 6.0 eV, we find Schottky barrier heights for holes between 1.2 and 2.3 eV. A central role in determining the Schottky barrier height is played by a potential step of between 0.4 and 1.8 eV that is formed at the $\mathrm{metal}|h-\mathrm{BN}$ interface and effectively lowers the metal work function. If $h-\mathrm{BN}$ is physisorbed, as is the case on fcc Cu, Al, Au, Ag, and Pt(111) substrates, the interface potential step is described well by a universal function that depends only on the distance separating $h-\mathrm{BN}$ from the metal surface. The interface potential step is largest when $h-\mathrm{BN}$ is chemisorbed, which is the case for hcp Co and Ti (0001) and for fcc Ni and Pd (111) substrates.