Nature of millimeter wave losses in low loss CVD diamonds
Abstract
The CVD diamonds dielectric loss mechanisms at the millimeter range of wavelengths are researched. The loss tangent tan δ at frequencies f≅50-200 GHz and temperatures t≅20-500 °C was measured. The loss tangent frequency dependence (at room temperature) is ∼1/ f at frequencies <140 GHz, due to electric conductance in non-diamond inclusions, and deviates upwards at f>140 GHz. From the comparison to the theory it follows that this deviation can be interpreted as exhibition of the nonintrinsic lattice loss connected with the lattice disorder induced one-phonon excitation of acoustic vibrations. The loss increase at temperatures >400 °C is sharper compared to the theoretical dependence for two-phonon intrinsic lattice loss (ILL). It can be connected with the loss due to dipole relaxation (of Debye type) with activation energy ∼0.56 eV. It was confirmed that the theoretical lower loss limit (determined by the ILL) in diamond is extremely low (particularly, at ambient temperatures, at least one order of magnitude lower than the lowest observed loss).
- Publication:
-
Diamond and Related Materials
- Pub Date:
- 2003
- DOI:
- 10.1016/S0925-9635(03)00199-7
- Bibcode:
- 2003DRM....12.1755G
- Keywords:
-
- Diamond properties and applications;
- Dielectric loss;
- Millimetre waves;
- Gyrotron windows