Laser method for the determination of the optical and thermal characteristics of diamond at high temperatures

The temporal and temperature dependences of the reflectivity, transmissivit y, and absorptivity and of the heat capacity of thermally thin diamond plat es were obtained in the course of heating up to 2500 degrees C at a rate of 10(3)-10(4) K s(-1) by laser radiation with lambda = 1.064 mu m. The tempe rature range in which significant irreversible changes take place in the op tical properties of diamond films was determined. These changes are associa ted with the formation of graphite microstructures in a thin surface layer about 100 nm thick. The formation of clusters of aromatic carbon atom group s with the sp(2) bonds is described. It is shown that the extinction coeffi cient of the modified layer is three orders of magnitude higher than that o f the unmodified layer.