AlN, ZnO thin films and AlN/ZnO or ZnO/AlN multilayer structures deposited by PLD for surface acoustic wave applications

(0002)-oriented AlN and ZnO thin films are deposited on C-sapphire substrates by pulsed laser deposition at 700 degrees C. Multilayered structures AlN/ZnO and ZnO/AlN are also grown on C-sapphire and investigated by X-ray diffraction, scanning electron microscopy and transmission measurements. Ellipsometry analysis is employed to investigate the stack of layers and the optical properties of thin films. This non-destructive analysis identified an intermediate layer between AlN and ZnO thin films for AlN/ZnO multilayer which didn't change the crystalline structure or piezoelectric properties of the multilayer. Surface acoustic wave velocities are respectively 5060ms(-1) for AlN and 5350ms(-1) for ZnO. In fact, investigations of surface acoustic wave (SAW) devices revealed a similar resonant frequency for both multilayers and in agreement with those measured for ZnO or AlN thin films.