Epitaxial Growth of Hexagonal Boron Nitride on Ir(111)

The formation of a hexagonal boron nitride (h-BN) layer through dissociation of borazine (B 3N 3H 6) molecules on Ir(111) has been investigated by a combination of X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure, temperature-programmed desorption, and low-energy electron diffraction. At low temperature (T = 170 K), molecular borazine adsorption occurs with the plane of the benzene-like ring parallel to the substrate. Dehydrogenation is observed at temperatures higher than 250 K and extends up to 900 K, with a maximum H 2 desorption rate around 300 K. Besides dehydrogenation, room temperature adsorption of borazine leads to the formation of atomic and molecular fragments due to the break-up of part of the BN bonds. The epitaxial growth of h-BN starts at temperature higher than 1000 K where an extended and long-range ordered layer is obtained. The presence of a corrugation in the h-BN layer with moiré periodicity of (13 × 13)/(12 × 12) BN/Ir unit cell is reflected in the double component structure of the B 1s and N 1s core level spectra.