DETERMINATION OF THE OPTICAL-CONSTANTS OF DIAMOND FILMS WITH A ROUGH GROWTH SURFACE

The determination of the optical constants n and k for polycrystalline diamond films with typical growth surface roughness a of the order of tens to hundreds of nanometers is both an important and a difficult p rocedure. A method for determining n, k and a for rough diamond films is presented here. It is based on theoretical expressions for the opti cal reflectance R and transmittance T for a free-standing thin film in corporating the effects of surface scattering at one surface. The usef ulness and validity of this approach are illustrated using experimenta l R and T data for diamond films. Simplified expressions for R and T a re also presented which are valid when scattering or absorption are su fficiently strong to cause interference effects in the films to be ave raged out.Prime novelty: Simple expressions for n, k and sigma are pre sented which will enable researchers to extract this important informa tion about the optical constants and surface roughness of their CVD di amond films.