Formation of boron nitride ultra-thin films on Si(111)

Chemical vapor deposition is employed to form hexagonal boron nitride (h-BN) monolayer films on Si(111) with a borazine precursor. The electronic structure and orientation of the films are analyzed by near edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). XPS analysis shows that monolayer-level stoichiometric BN films were formed. The B K-edge NEXAFS spectra show two discrete peaks that have graphite-like polarization dependence in the low-energy region. Polarization dependence analysis of the NEXAFS indicates that the BN films had two-dimensional orientation on the Si(111) substrate. Based on the density functional theory calculations, these discrete peaks are assigned to pi* peaks at an intact h-BN site and edge B-H site. Comparison with the electronic structures of bulk h-BN and h-BN/Ni(111) clarifies that the interaction between the BN layer and Si substrate was very small. This indicates that the h-BN monolayer was physisorbed on Si(111), making a steep interface and conserving the intrinsic electronic structure.