Simple correlation between optical absorption and thermal conductivity of CVD diamond

Abstract The relationship between the thermal conductivity and optical absorption was investigated for over 60 samples of CVD diamond grown in ten different laboratories. The thermal conductivities k ∥ and k ⊥ (with heat flow parallel or perpendicular to the plane of the sample) were measured by steady state and laser flash techniques respectively. A simple and inexpensive apparatus is described to enable accurate and rapid measurement of the optical absorption coefficient α averaged over the visible spectrum. A clear correlation was found between k ∥ or k ⊥ and α , which can be fitted using a particularly simple expression with coefficients for k ∥ vs. α which are slightly different from those for k ⊥ vs. α . The behavior can be used to obtain estimates of k ∥ or k ⊥ (within uncertainties of approximately ± 3 W cm −1 K −1 ) from optical absorption measurements.