Bonding structure and mechanical properties of B-C-N thin films synthesized by pulsed laser deposition at different laser fluences

Abstract

Boron carbon nitride (B-C-N) thin films have been grown by pulsed laser deposition under different laser fluences changing from 1.0 to 3.0J/cm2. The influence of laser fluence on microstructure, bonding structure, and mechanical properties of the films was studied, so as to explore the possibility of improving their mechanical properties by controlling bonding structure. The bonding structure identified by FT-IR and XPS indicated the coexistence of B-N, B-C, N-C and NC bonds in the films, suggesting the formation of a ternary B-C-N hybridization. There is a clear evolution of bonding structure in the B-C-N films with the increasing of laser fluence. The variation of the mechanical properties as a function of laser fluence was also in accordance with the evolution of B-C and sp3 N-C bonds whereas contrary to that of sp2 B-N and NC bonds. The hardness and modulus reached the maximum value of 33.7GPa and 256GPa, respectively, at a laser fluence of 3.0J/cm2, where the B-C-N thin films synthesized by pulsed laser deposition possessed the highest intensity of B-C and N-C bonds and the lowest fraction of B-N and NC bonds.