Carbon overcoats with controlled properties: non-destructive ellipsometry evaluation

Abstract

Abstract Hard carbon thin films have been prepared on fused silica substrates by r.f. plasma deposition and magnetron sputtering using mixtures of argon and methane gases. By controlling the deposition power and gas pressure amorphous carbon films with optical energy gaps ranging from zero to above 2.0 eV were prepared and characterized by variable-angle-of-incidence spectroscopic ellipsometry (VASE). A parametric model was developed based on the measured optical constants as function of optical energy gap which allows the measurement of the thickness and optical constants of thin carbon films on opaque substrates with the VASE technique only. Applications of this model to the characterization of carbon overcoats on magnetic disk structures are presented as well.