High temperature thermal conductivity of free-standing diamond films prepared by DC arc plasma jet CVD

Free-standing diamond films with 1.68 mm in polished thickness have been prepared by DC arc plasma jet CVD. By means of simply changing the placing orientation of diamond films along the laser transmission direction while testing, the through-thickness thermal conductivity (kappa(perpendicular to)) together with the in-plane (kappa(//)) thermal conductivity of free-standing diamond films were measured by laser flash technique over a wide temperature range. Results show that the thermal conductivity kappa(perpendicular to) and kappa(//) of free-standing diamond films are up to 1916 and 1739 Wm(-1) K-1 at room temperature, respectively, showing small anisotropy (9%), and following the relationship kappa similar to T-n as temperature rises. The conductivity exhibits similar value compared to that of high-quality single crystal diamond above 500 K for both through-thickness and in-plane directions of CVD diamond films. The effects of impurities and grain boundaries on thermal conductivity of diamond films with increasing temperature were discussed. (C) 2014 Elsevier B.V. All rights reserved.