CHARACTERISTICS OF DIAMOND-LIKE CARBON-FILMS FORMED BY A HYBRID LASER PLASMA ABLATION OF GRAPHITE

A novel laser-plasma technique was used for the deposition of diamond-like carbon (DLC) films. The films were deposited in vacuum and in hydrogen ambients and the substrate temperature was varied from 25 to 860-degrees-C. The DLC films were characterized by spectroscopic ellipsometry, Fourier transform infrared (FTIR) and Raman spectroscopy. The sp3/sp2 fraction was estimated by using the effective number of valence electrons, n(eff), from n and k measurements. The Raman disorder mode, or D band and the Raman-allowed graphitic mode, or G band, were deconvoluted using gaussian functions. A correlation was obtained between the sp3 concentration, (C(sp3)), and the D band shift. Specifically, an increase in C(sp3) resulted in a downward shift in the D band. The results are supported by FTIR measurements indicating a combination of disordered and sp3 phonon absorption bands for the films deposited in a vacuum ambient and stabilized sp3 bonds for the films deposited in a hydrogen ambient.