“…Metallic electrodes promoting the growth of highly c-axis oriented AlN films with single polar orientation and contributing to the confinement of the mechanical energy in the piezoelectric layer are the candidates of choice [8,9]. Metals most frequently used in BAW applications are W [10], Pt [6], and Mo [11], although many others (Al, Ta, Ti, Cu, Cr, Au, Ru, Ir) have been investigated [9,12,13,14]. So far, the besttextured AlN films deposited by sputtering have been obtained on Pt and Ir metallic surfaces, in which the {111} planes exhibit hexagonal symmetry, providing AlN films with very low values of the full width at half maximum (FWHM) of the rocking-curve (RC) around the 00·2 peak (around 0.9º for 1 μ m-thick films) [8,14] and very high piezoelectric activity.…”