Optical properties of DLC films deposited by the saddle field fast atom neutral beam source

A saddle field fast atom beam source (FAB) was used to produce diamond-like carbon (DLC) coatings on glass substrates by dissociation and ionisation of acetylene (C2H2) in a low pressure vacuum. The UV absorbance of deposited films was measured by UV-vis spectrometer. The optical band gap Eg, of these films was measured by Tauc formula as a function of deposition current and pressure. The UV absorption of DLC films was found lower for the whole wave number range (400-1100 nm) at lower deposition current 0.4 A, whereas the UV absorption with photon energy does not appear to depend at deposition pressure level particularly for higher deposition current. The value of optical band gap of films was found higher for higher deposition current 0.8 A. The sp3 content inside the film was found to be higher with higher deposition current which affected the optical band gap.