Effect of nitrogen pressure on structure and optical properties of pulsed laser deposited BCN thin films

Amorphous boron carbon nitride (BCN) thin films were deposited on Si (100) and quartz substrates by laser ablation of a boron carbide (B4C) target in nitrogen atmosphere. The effects of the nitrogen pre ssure (pN2) on the film deposition rate, composition, structure and optical properties were investigated. The film deposition rate was measured by a surface profiler, which increased from 3.4 to 6.25 nm/min at elevated pN2. Structure and composition of the films were investigated by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) spectroscopy. FTIR and XPS analyses indicated that the as-deposited BCN films contained B–C, N–C and B–N chemical bonds, implying the formation of ternary BCN compounds. The nitrogen content in the films increased gradually and then saturated up to ∼ 26 at.% at 10 Pa pN2. The optical band gap (Eg) increased from 3.78 to 3.92 eV with increasing pN2 from 2 to 15 Pa. The evolution of Eg is in accordance with the change of film compositions and bonding states.