TITLE: Phonon scattering by grain boundaries in CVD diamond

ABSTRACT:
 

In the chemical vapor deposited diamond, the comparison of the measured thermal conductivity with theoretical calculations shows that the heat transport due to phonons is limited by several scattering mechanisms, that is, by the scattering from point defects extended defects of nanoscale dimensions, dislocations, grain boundaries and microcracks.

Moreover at high temperatures phonon-phonon scattering must be included. A recently proposed theory for grain boundaries considering them as a periodic array of dislocations shows the occurence of phonon scattering processes not accounted by the Klemens theory of thermal conductivity. It can be seen that a grain boundary works as a difraction grating producing difraction spectra of various orders. The Klemens theory correspond to order zero.

With this approach to grain boundaries the thermal conductivity in CVD diamond is evaluated and compared with experimental data. At low temperatures the major part of the phonon scattering turns out to be due to grain boundaries.

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