AlN, ZnO thin films and AlN/ ZnO or ZnO/AlN multilayer structures deposited by PLD for surface acoustic wave devices
Résumé
Surface acoustic wave (SAW) devices were fabricated on ZnO and AlN thin films deposited on C-sapphire substrates by pulsed laser deposition at 700°C. The experimental results showed that AlN and ZnO films are (0002)-oriented and surface acoustic wave velocity on C-sapphire is respectively equal to 5060 m.s-1 for AlN and to 5350 m.s-1 for ZnO. Multilayer structures AlN/ZnO and ZnO/AlN are also realized on C-sapphire and investigated by X-ray diffraction, SEM observations, spectroscopic ellipsometry and transmission measurements. Ellipsometry analysis shows an intermediate layer between AlN and ZnO thin films for AlN/ZnO multilayer; this one doesn’t lead to a change in crystalline structure or piezoelectric property of multilayer. In fact, analyses of the SAW devices revealed that Rayleigh waves were detected and their resonant frequencies are the same for both multilayers and in agreement with those measured for ZnO or AlN thin films in SAW filters.