CHARACTERIZATION BY UV-VISIBLE AND IR SPECTROSCOPY OF THIN DIAMOND-LIKE CARBON-FILMS PREPARED BY LASER-ARC

A new deposition method with laser-induced controlled vacuum arc (Laser-Arc) was used for the thin film deposition of diamond-like carbon (DLC) films onto different materials (ZnSe, KRS-5, Coming 7059, KBr, KCl and NaCl). Carbon films between 50 nm and 200 nm thick deposited at different deposition rates (0.1-2 nm s-1) and pulse durations (37 mus, 100 mus) were studied. A special moveable substrate holder was used to deposit an all-face protective DLC coating onto the surfaces of the KRS-5, ZnSe and salt substrates. The coated substrates were characterized by UV-visible, near-IR and Fourier transform IR spectroscopy in the wave-number range between 400 cm-1 and 50 000 cm-1. Transmission and reflection measurements of the films on Coming 7059 were used to determine the absorption coefficient and the optical gap energy. They correlate with the deposition conditions. Transmissions above 90% were observed in the IR spectra of the double-sided coatings. However, in the ranges 6000-3500 cm-1, 2800-1700 cm-1 and 1400-1000 cm-1 the coatings on ZnSe and KRS-5 show antireflection properties. These coatings are usable as protective films for KCl, NaCl and KBr against water with a high transmission for IR optical laser materials, e.g. a CO2-laser at a wavelength of 10,6 mum, and as protective films for toxic KRS-5 (TlBr/TlI). The DLC coatings on the ZnSe substrates show high adhesion. The film can be removed only by polishing with diamond paste.