Influence of nitrogen pressure on bonding structure and mechanical properties of pulsed laser deposited BCN thin films

Boron carbon nitride (BCN) thin films were deposited on Si (100) substrates by pulsed laser deposition (PLD) under various nitrogen pressures (p(N2)) changing from 2.5 to 5.0 Pa. The influences of p(N2) on the deposition rate, bonding structure and hardness of the films were studied, so as to explore the possibility of improving their mechanical properties by controlling bonding structure. The deposition rate was found to be increased with increasing p(N2), while the hardness of the films fluctuated in the scope of 14.8 to 25.2 GPa. The bonding structure identified by X-ray photoelectron spectroscopy indicated the coexistence of B-N, B-C, and N-C bonds in the films, suggesting the formation of a ternary B-C-N hybridization. The variation of hardness as a function of p(N2) was in accordance with the evolution of C-B and sp(3) N-C bonds whereas contrary to that of sp(2) h-B-N bond. The hardness reached the maximum value of 25.2 GPa at p(N2) = 3.5 Pa, where the BCN films possessed the highest intensity of C-B and sp(3) N-C bonds and the lowest fraction of sp(2) h-B-N bond. (C) 2015 Elsevier B.V. All rights reserved.