Surface acoustic wave properties of aluminum oxide films on lithium niobate

Aluminum oxide (Al2O3) films have been deposited on lithium niobate (LiNbO3) substrates by electron beam evaporation without any interlayer between them to ensure a good adhesion of the Al2O3 films to LiNbO3 substrates. As Al2O3 thin films can sufficiently increase the surface acoustic wave (SAW) velocity, they can be used to improve the performance of the SAW device. The SAW phase velocity in the Al2O3/LiNbO3 structure was found to increase with the insertion of an Al2O3 film, which can be attributed to the stiffening effect of the Al2O3 layer. The velocity change ratio of SAW was about 4.39% (at 304 MHz) for the Al2O3 (9.7 μm)/LiNbO3 sample. A comparison with other findings in literature reveals that this result is better than what is available from diamond-like carbon/SiC buffer layer/LiNbO3 structure, whose the velocity change ratio is 2%.