Piezoelectric AlN films for FPW sensors with improved device performance

Reactively sputtered piezoelectric aluminum nitride (AlN) films for flexural plate wave (FPW) electroacoustic sensors equipped with buried interdigital transducers (IDTs) for sensing in liquids were fabricated and characterized. In order to assess the crystallographic and elastic film properties, residual film stress, and piezoelectric response, comprehensive analyses were performed on AlN layers and bimorph AlN structures, including X-ray diffraction, atomic force microscopy, and nanoindentation, in combination with analysis of the piezoelectric charge coefficient d(33,f). To demonstrate the applicability of the optimized AlN films to electro-acoustic devices, IDT equipped devices were fabricated and characterized by means of laser Doppler vibrometry