SIMPLE CORRELATION BETWEEN OPTICAL-ABSORPTION AND THERMAL-CONDUCTIVITY OF CVD DIAMOND

The relationship between the thermal conductivity and optical absorpti on was investigated for over 60 samples of CVD diamond grown in ten di fferent laboratories. The thermal conductivities kappa(parallel to) an d kappa(parallel to) (with heat flow parallel or perpendicular to the plane of the sample) were measured by steady state and laser flash tec hniques respectively. A simple and inexpensive apparatus is described to enable accurate and rapid measurement of the optical absorption coe fficient alpha averaged over the visible spectrum. A clear correlation was found between kappa(parallel to) or kappa(perpendicular to) and a lpha, which can be fitted using a particularly simple expression with coefficients for kappa(parallel to) vs. alpha which are slightly diffe rent from those for k(perpendicular to) vs. alpha. The behavior can be used to obtain estimates of kappa(parallel to) or kappa(perpendicular to) (within uncertainties of approximately +/-3 W cm(-1) K-1) from op tical absorption measurements.