Amorphous diamond-like carbon film prepared by pulsed laser deposition with application of pulsed negative bias voltage

Abstract

Amorphous diamond-like carbon films were prepared by pulsed laser deposition with a synchronized application of pulsed negative bias voltage to the substrate. A beam from a Nd:yttrium–aluminum–garnet laser (1064 nm) was radiated to a graphite target at a laser fluence of 10 J/cm2. The negative bias voltage was changed from 0 to 10 kV at a repetition rate of 10 Hz. The film was deposited on a Si (111) substrate at a chamber pressure of 5×10−5 Torr for 120 min. The effects of bias voltage on the structure of the film were discussed on the basis of the measured deposition rate, Raman spectra, refractive index, dynamic hardness, and surface roughness. The effect of self-sputtering on deposition rate was observed at a negative bias voltage above 0.6 kV. The application of bias voltage increased the fraction of sp3 configuration in the film and made the film surface smoother. In particular, the application of 3 kV gave the largest fraction of sp3 bonding, and formed the hardest and smoothest film. Bias voltage above 5 kV, however, drastically reduced the hardness of the film.