Pulsed laser deposition of hydrogenated amorphous diamond-like carbon films from a polymer target

Hydrogenated amorphous diamond-like carbon (a-DLC:H) films have been prepared by pulsed laser ablation of a polymer target in the presence of hydrogen (H-2) gas. The growth rate of these films was found to be highly dependent on the deposition temperature and the amount of H-2 gas used during the deposition process. The optical band gap of these a-DLC:H films changed in a wide range (0.25-2.5 eV) with substrate temperature and H-2 pressure, and was found to be highly correlated to the ratio of sp(3)/sp(2) in the film. The gap reached a maximum in a temperature range between 100 and 200 degrees C and had small values at either lower or higher temperatures. With increasing H-2 pressure, the band gap increased monotonically and saturated around 0.5 mbar. It was found that the refractive index and the imaginary part of dielectric constant of these a-DLC:H films monotonically increased with decreases in the wavelength of the probing beam. It was also found that these laser derived a-DLC:H films could be made either completely insulating [similar to 10(-11) (Omega cm)(-1)] or conducting [similar to 1 (Omega cm)(-1)] by simply varying the deposition temperature and H-2 pressure. Very little photoconduction has been observed in these a-DLC:H films. (C) 1996 American Institute of Physics.