Increase in Adhesion Strength and Thickness of Cubic Boron Nitride Thin Films by Silicon Addition

Compositionally gradient boron nitride with silicon (BN:Si) thin films have been prepared on silicon (100) substrates by radio frequency magnetron sputtering. A hexagonal boron nitride (h-BN) target with uneven distribution of silicon plates was used for the deposition. The present study was focused on the investigation of the morphology, the microstructure, the determination of silicon composition, the bonding structure and the micro-hardness using scanning electron microscopy (SEAM), Rutherford back scattering spectroscopy (RBS), Fourier transform infra-red spectroscopy (FT-IR) and micro-hardness testing with a Vickers indenter. The BN:Si thin films with the thicknesses of 100 similar to 850 run were not peeled off as compared to the boron nitride thin films with the same thicknesses. Increasing the Si content of the boron nitride thin films induced a decrease in fraction of spa bonding. The cubic boron nitride (c-BN) thin film with silicon addition was deposited with a thickness of 850 nm at 5.2 mol% silicon content. On the other hand, the hardness was 72 GPa and the young's modulus was 286 GPa. Since the c-BN:Si thin film was peeled off from silicon substrate at a few weeks after the deposition, compressive stress was not completely released by silicon addition.