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Aluminum nitride is an excellent electrical insulator and important piezoelectric material making it suitable for a wide range of applications in electronics and optoelectronics. However, to exhibit and preserve those piezoelectric properties, care has to be taken during manufacturing process. Indeed, the c-axis crystalline orientation of AlN is a necessary condition for piezoelectricity. Therefore, the goal of this paper is to compare AlN films grown on (100) silicon substrate by pulsed reactive DC sputtering at 400 °C on top of three different metallic underlayer electrodes (Ti/Pt, Cr/Pt, and AlN/Cr/Pt) by preserving the crystalline properties not only at room temperature but also at high temperatures. Among all deposited AlN films on top of the metallic underlayer electrode, only AlN/Cr/Pt has kept its crystallinity up to 950 °C. [ABSTRACT FROM AUTHOR]

This paper presents a method to determine the mechanical properties of piezoelectric thin films. The vibrational behavior of microcantilevers and clamped-clamped beams actuated by aluminum nitride (AlN) piezoelectric films were analyzed in order to investigate the suitability of these devices as characterization tools. Different geometries of resonators composed of a free-standing structure made up of a TiPt/AlN/TiPt piezoelectric stack were tested. The out-of-plane motion of the resonators was assessed by laser Doppler vibrometry. An AlN Young's modulus of about 200 GPa was extracted from resonance-frequency measurements by means of Comsol software simulations that allow taking into account AlN underetching. This value of Young's modulus was compared to the one measured by a nanoindentation technique. The quality of crystallinity was also assessed using X-ray diffraction (XRD) measurements. We then estimated the residual stress (about 200 MPa) using an interferometry measurement. [ABSTRACT FROM AUTHOR]