Yoshiaki Kumazawa

The measurement of thermal properties of diamond

Abstract 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.

Growth Rate and Surface Morphology of Diamond Homoepitaxial Films on Misoriented (001) Substrates

Homoepitaxial films were grown on misoriented diamond(001) substrates using microwave plasma-assisted chemical vapor deposition with a methane and hydrogen gas mixture. The dependence of growth rate and surface morphology on methane concentration, substrate temperature and off-angle was investigated. The growth rate dependence was significant for a growth at a high substrate temperature (1000° C) and low methane concentration (1%), suggesting the surface migration distance of the nanometer order. A flat surface was observed macroscopically and microscopically for films grown on off-substrates at a high substrate temperature and low methane concentration.