THE OPTICAL DIELECTRIC FUNCTION OF AMORPHOUS-CARBON FILMS

Amorphous carbon, deposited as a thin film (similar to 47 nm thick) on a silica prism, has been characterised, for the first time over a ran ge of wavelengths, using attenuated total internal reflection. By meas uring angular dependent reflectivities from the prism-carbon interface in the region of the critical angle with subsequent fitting of the da ta to Fresnel theory, both the real and imaginary parts of the dielect ric function are obtained. The wavelength dependence of these two vari ables has thereby been established between 450 and 840 nm. Extension o f this range for the imaginary component to 200 nm, by optical absorpt ion measurements, has allowed discrimination between two different mod els describing the electron states at the band edge in this material.