Influence of structural characteristics on the thermal conductivity of polycrystalline diamond films

By analyzing the signal formed by the photoacoustic effect as a function of the light modulation frequency, it is shown that this effect may be used to determine the thermal conductivity of diamond materials. The method is checked experimentally for two types of polycrystalline diamond films grown by chemical vapor deposition with the gaseous medium activated by a dc discharge and a microwave discharge. The data obtained on the thermal conductivity of the films are discussed with reference to the results of an investigation of the optical absorption, Raman light scattering, and cathodoluminescence of similar films. It is shown that the thermal conductivity of polycrystalline diamond films depends on the structural characteristics, which are determined by the deposition conditions. Fiz. Tverd. Tela (St. Petersburg) 40, 1221–1225 (July 1998)