Evidence for the layered structure of c-BN films by in situ REELS analyses and depth profiling

In situ Reflection Electron Energy Loss Spectroscopy REELS.analyses, performed at various primary electron energies, enable us to distinguish between sp3 and sp2 bonding in BN films. Consequences on the c-BN growth modelling are discussed based on the result that polycrystalline cubic BN films grown using IBAD always exhibit a superficial zone of three to four sp2 bonded monolayers. Increasing the ion energy enlarges the sp2 superficial zone, while ion beam etching at grazing incidence decreases its thickness. In addition, REELS depth profiling, based on the complementary use of ion beam etching at grazing incidence and REELS analyses, clearly evidences the phase distribution within the c-BN film and reveals a layered structure including a thin layer of a-BN close to the substrate followed by an h-BN basal layer and then by a nearly pure c-BN volume. q1999 Elsevier Science B.V. All rights reserved