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

In situ Reflection Electron Energy Loss Spectroscopy (REELS) analyses, perf ormed at various primary electron energies, enable us to distinguish betwee n sp(3) and sp(2) bonding in BN films. Consequences on the c-BN growth mode lling are discussed based on the result that polycrystalline cubic BN films grown using IBAD always exhibit a superficial zone of three to four sp(2) bonded monolayers. Increasing the ion energy enlarges the sp(2) 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 Nm and reveals a layered structure incl uding 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. (C) 1999 Elsevier Science B.V . All rights reserved.