THE THERMAL-CONDUCTIVITY OF ISOTOPICALLY ENRICHED POLYCRYSTALLINE DIAMOND FILMS

The thermal conductivity of a chemically vapor deposited (CVD) diamond film containing 0.07% C-13 was measured as a function of temperature by ac and dc techniques and compared to CVD diamond with a natural isotopic abundance of 1.07% C-13. Unlike the single-crystal case where a large isotope enhancement effect has been reported, no increase in the thermal conductivity was observed in isotopically enriched CVD diamond films. The absence of an isotope effect in CVD diamond films indicates that a phonon scattering mechanism other than isotope scattering dominates in CVD diamond.