The measurement of thermal properties of diamond

Steady state and laser-flash methods were developed for measuring the thermal conductivity of various types of diamond films; single crystal by homoepitaxial growth, single crystal synthesized by a high-pressure and high-temperature (HP/HT) method and polycrystalline film grown by chemical vapor deposition(CVD). The dependence of thermal conductivity on impurity, crystallinity and grain size was studied. Single crystals obtained. by homoepitaxial growth showed isotropic thermal conductivity, while polycrystalline films grown by microwave plasma assisted CVD showed anisotropic thermal conductivity. The concentration of nitrogen was observed to affect the thermal conductivity of type Ib single crystal diamond synthesized by the HP/HT method. In the case of polycrystalline diamond, thermal conductivity was found to depend on crystallinity and grain size. (C) 1997 Elsevier Science S.A.