Nondestructive Dynamic Characterization of Nanocrystalline Diamond Membranes for Flexural Plate Wave Sensors

Nanocrystalline diamond (NCD) is a promising material for the fabrication of highly sensitive flexural-plate-wave (FPW) sensors. The design of FPW sensors requires the determination of the mechanical properties of a vibrating thin-film membrane. In this paper, a method to investigate the mechanical resonance of NCD membranes is presented. Membranes with lateral dimensions in the millimeter range and 1.2-
$muhboxm$
thick were excited in air by a loudspeaker, and the resonance mode shapes were recorded optically with a stroboscopic interferometer. The resonance frequencies helped in determining directly the mechanical parameter of interest for the design of diamond-based FPW devices and the residual stress in the NCD layer. This method allows the rapid investigation of prototype materials without requiring an integrated transduction system and can be applied to analyze structures with the actual dimensions of FPW sensors. The experimental results are used to assess the sensing properties of FPW devices with NCD membranes, which are enhanced with respect to classical materials such as silicon-based materials.