Surface reactions of low-energy carbon ions with boron nitride thin films

The chemical reactions between hyperthermal species from a methane plasma and the boron nitride surface have been studied. In this work we report an x-ray photoemission study of the boron nitride with varying degrees of carburization. The carbon ions react, forming C–B and C–N bonds; for surface carbon concentration, smaller than ,∼0.30, C–B bonds are formed, while for higher surface carbon concentrations C–N bonds are also observed. In addition, the binding energy difference between the N1s and B1s core levels increases with increasing carbon content of the film. These chemical shifts are interpreted in terms of the decrease of the ionicity of the material as a consequence of the increase in the number of C–B and C–N bonds. For surface carbon concentration higher than 0.30, amorphous carbon is also formed that grows and finally forms a surface layer. The valence band spectra of the BNC compounds show that the density of states filling the gap at about 15 eV between the two characteristic peaks of the valence band of BN, marking the nitrogen 2s orbitals and the boron and nitrogen 2p electrons and the orbital hybridization between the 2s of boron and 2p states, increases with increasing carbon fluence as a consequence of the hybridization with carbon orbitals.