Non-equilibrium acoustic phonon propagation in CVD diamond films

Abstract We have studied the mechanism of heat transfer under pulsed excitation at low temperatures while measuring the propagation of non-equilibrium acoustic phonon packets across a CVD diamond film. Results are presented on the measurements of acoustic phonon packets propagating across the high quality CVD diamond films with 0.25 and 0.35 mm thickness. Two types of phonon generator were employed: laser heated Au/Ti films deposited onto the sample, and photoexcited buried implanted layers. A superconducting Al GR -based bolometer served as the phonon detector. The results obtained essentially differ from those for natural diamond: under photoexcitation of the buried implanted layer the bolometer response times are larger by an order of magnitude than those for natural diamond, and the shape of response has a clearly pronounced diffusive character. Possible mechanisms of response broadening are discussed, including the scattering of high-frequency phonons at grain boundaries.