Synthesis and characterization of boron carbon nitride films by radio frequency magnetron sputtering

Boron carbon nitride (BCN) films were deposited on silicon substrates by radio frequency (r.f.) (13.56 MHz) magnetron sputtering from hexagonal boron nitride (h-BN) and graphite targets in an Ar–N2 gas mixture of a constant pressure of 1.0 Pa. During deposition, the substrates were maintained at a temperature of 400°C and negatively biased using a pulsed voltage with a frequency of 330 kHz. Different analysis techniques such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD) and scanning Auger electron microscopy (SAM) were used for characterization. In addition, the mechanical and tribological properties of the films were investigated by nano-indentation and micro-scratching. The carbon concentration in the films could be adjusted by the coverage area of a graphite sheet on the h-BN target, and decreased with increasing bias voltage. It was found that the ternary compound films within the B–C–N composition triangle possessed a less ordered structure. BN, BC and CN chemical bonds were established in the films, and no phase separation of graphite and h-BN occurred. At zero bias voltage, amorphous BC2N films with atomically smooth surface could be obtained, and the microfriction coefficient was 0.11 under a normal load of 1000 μN. Hardness as determined by nano-indentation was usually in the range of 10–30 GPa, whereas the Young’s modulus was within 100–200 GPa.