Structural, electrical and piezoelectric properties of LiNbO_3 thin films for surface acoustic wave resonators applications

摘要

In this work, 0.30 μm thick LiNbO_3 layers have been deposited by sputtering on nanocrystalline diamond/Si and platinised Si substrates. The films were then analyzed in terms of their structural and optical properties. Crystalline orientations along the (0 1 2), (1 0 4) and (1 1 0) axes have been detected after thermal treatment at 500 ℃ in air. The films were near-stoichiometric and did not reveal strong losses or diffusion in lithium during deposition or after thermal annealing. Pronounced decrease of the roughness on top of the LiNbO_3 layer and at the interface between LiNbO_3 and diamond was also observed after annealing, compared to the bare nanocrystalline diamond on Si substrate. Furthermore, ellipsometry analysis showed a better density and a reduced thickness of the surface layer after post-deposition annealing. The dielectric constant and losses have been measured to 50 and less than 3.5%, respectively, for metal/insulator/metal structures with 0.30 μm thick LiNbO_3 layer. The piezoelectric coefficient d_(33) was found to be 7.1 pm/V. Finally, we succeeded in switching local domain under various positive and negative voltages.