The optical dielectric function of amorphous carbon films

Abstract

Amorphous carbon, deposited as a thin film (∼47 nm thick) on a silica prism, has been characterised, for the first time over a range of wavelengths, using attenuated total internal reflection. By measuring angular dependent reflectivities from the prism-carbon interface in the region of the critical angle with subsequent fitting of the data to Fresnel theory, both the real and imaginary parts of the dielectric function are obtained. The wavelength dependence of these two variables has thereby been established between 450 and 840 nm. Extension of this range for the imaginary component to 200 nm, by optical absorption measurements, has allowed discrimination between two different models describing the electron states at the band edge in this material.