Determination of sp3/sp2 bonding ratio in diamond-like films of a-C:H

A new method to determine the relative concentration of sp3 and sp2 hybridized carbon through the complex dielectric constant deduced from optical measurements of transmittance and reflectance is reported. In the method a gaussian-like band approximation for π − π* electronic bands is assumed and Wemple-DiDomenico model is applied to obtain thesp3/sp2 ratio. The values of the ratio obtained applying this method are compared with those obtained by IR and NMR spectroscopies