Regensburg 2000 – scientific programme
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DS: Dünne Schichten
DS 34: Mechanische Eigenschaften
DS 34.1: Fachvortrag
Thursday, March 30, 2000, 11:15–11:30, H32
Untersuchung der mechanischen Eigenschaften freistehender polykristalliner CVD-Diamantschichten durch lasergenerierte akustische Oberflächenwellen — •C.M. Flannery1, M.D. Whitfield2, and R.B. Jackman2 — 1Paul-Drude-Institut für Festkörperelektronik, Abteilung Nanoakustik, Hausvogteiplatz 5-7, D-10117 Berlin — 2Electronic Engineering Department, University College London, Torrington Place, London WC1E 7JE, England
Knowledge of the mechanical and elastic properties of polycrystalline diamond films is necessary if one is to use these materials for mechanical, acoustic and sensing purposes. At present there is very little information available about these properties for films greater than a few microns thickness. In this work we inspect free-standing polycrystalline films of thickness in the 100s of microns range by means of wideband surface acoustic and Lamb waves with frequencies up to 200 MHz, generated using thermoelastic excitation by a short-pulse duration (0.5 ns) nitrogen laser and detection with a PVDF foil with steel-wedge transducer. From analysis of the acoustic wavepackets one may measure the Rayleigh wave and bulk wave velocities in the material, and from these obtain the material elastic properties. We are also able to show evidence of elastic anisotropies and nonuniformities in the material and correlate these features with grain size and orientation, and quality and roughness of the film. These results represent a considerable step forward in acoustic characterisation of CVD diamond, in terms of accurate and useful acoustic and elastic measurements and as a nondestructive testing tool of film quality.