Spectroellipsometric characterization of nanocrystalline diamond layers

The complex refractive index and the layer thickness of nanocrystalline diamond films was determined by ex situ variable angle spectroscopic ellipsometry in the wavelength range of 191–1690 nm. During the layer depositions argon, methane and hydrogen gases were used as source gases. The combined effect of argon addition and substrate bias was investigated in the microwave plasma assisted chemical vapor deposition of diamond. Multilayer optical models were constructed for the evaluation of the measured ellipsometric spectra. The effective medium approximation and the Lorentz dispersion relation were employed for the modeling of the optical properties of the diamond films.