UHF acoustic attenuation and quality parameter limits in the diamond based HBAR

Ultra high frequency attenuation limits in synthetic IIa diamond single crystal were studied. The investigations were provided by High-overtone Bulk Acoustic Resonator “Al/AlN/Mo/(100) diamond”. It was shown, that the change of Akhiezer´s attenuation regime to Landau-Rumer one takes place at f ≈ 1 GHz. The experimental results on the quality parameter showed Q×f ≈ 1.8·10¹³ Hz for Akhiezer´s regime, and Q×f ≈ f×1.8·10⁴ Hz for Landau-Rumer regime. As a consequence on a higher frequencies diamond single crystal has more preferred acoustic parameters including a lower acoustic attenuation in comparison with known acoustoelectronic materials.