Relative fraction of sp3 bonding in boron incorporated amorphous carbon films determined by X-ray photoelectron spectroscopy

Boron incorporated amorphous carbon (a-C:B) films were deposited by a filtered cathodic vacuum arc system using various percentage of boron mixed graphite cathodes. X-ray photoelectron spectroscopy (XPS) was employed to determine the properties of the films as a function of boron concentration. Deconvolutions of the XPS C 1s core level spectra were carried out using four different components. The relative fraction of sp3 bonding was then evaluated from the area ratio of the peaks at 285.0, 284.1 eV which were individually attributed to sp3 C-C, sp2 C=C hybridizations. The results showed that the sp3 content of a-C:B film decreases from 73.8 to 58.6% for the films containing boron from 0.59 to 2.13 at.%, and then gradually reduced to 42.5% at a slower rate with boron concentration up to 6.04 at.%. Furthermore, a series of a-C:B films with fixed boron content (2.13 at.%) were prepared to identify the relationship between sp3 bonding and substrate bias. It was found that the fraction of sp3 bonding increased from 50.28% at the bias voltage of 0 V and reached a maximum value of 66.3% at -150 V. As the bias voltage increased up to -2000 V, the sp3 content decreased sharply to 43.9%