Atomic layer-by-layer deposition of h-BN(0001) on cobalt: a building block for spintronics and graphene electronics

X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and Raman measurements demonstrate that macroscopically continuous hexagonal BN(0001) (h-BN) multilayer layer films can be grown by atomic layer deposition on Co(0001) substrates. The growth procedure involves alternating exposures of BCl₃ and NH₃ at 550 K, followed by annealing in ultrahigh vacuum above 700 K to induce long-range order. XPS data demonstrate that the films have a consistent B:N atomic ratio of 1:1. LEED data show that the BN layers are azimuthally in registry, with an estimated domain size of ∼170 Å. The films are continuous over a macroscopic (1 cm × 1 cm) area as demonstrated by the fact that exposure of a h-BN(0001) bi-layer film to ambient at room temperature yields no observable Co oxidation, although some N oxidation is observed, and long range order is lost. The ability to grow large area, continuous multilayer BN films on Co, with atomic level control of film thickness, makes possible an array of magnetic tunnel junction and spin filter applications. (paper)