Keiichiro Tanabe

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.

High power durability of diamond surface acoustic wave filter

The power durability of the ZnO/diamond surface acoustic wave (SAW) filter was investigated and compared with the LiTaO/sub 3/ SAW filter. The ZnO/diamond SAW filter maintained linearity of the input-output relation up to the input power of 36 dBm at 2.90 GHz, whereas the LiTaO/sub 3/ SAW filter, which operated at 822 MHz, was nonlinear above the input power of 23 dBm and degraded significantly at 27.7 dBm. The input power dependence of the time to failure was also investigated for both SAW filters. It was found that the ZnO/diamond SAW filter was durable for 8 dB higher input power than that of the LiTaO/sub 3/ SAW filter even at 3.5 times higher frequency. These results indicate the extremely high power durability of the ZnO/diamond SAW filter.