EFFECTIVE-MEDIUM THEORY FOR THE OPTICAL-PROPERTIES OF DIAMOND AND DIAMOND-LIKE FILMS

We present effective-medium calculations of the optical properties of chemical vapor deposition-grown diamond films, under the assumption th at these films are contaminated by various kinds of defects. Two types of defective films are considered: (i) a distribution of graphite cry stallites in diamond, with each crystallite small compared to the wave length of light; and (ii) a rough diamond-air interface. The calculati ons are carried out by treating the film in case (i) and rough surface layer in case (ii) as homogeneous media with effective dielectric pro perties. In both cases, we find characteristic modifications of the fr equency-dependent reflectivity. The experimentally observed reflectivi ty of a diamond film is very well reproduced by our calculation over a broad frequency range between 2 and 10 eV.