Effect of growth conditions on microstructure of BiFeO3-0.33BaTiO(3) films and performance of bulk acoustic wave resonators

Artikel i vetenskaplig tidskrift, 2014

The effect of growth conditions on the microstructure of BiFeO3-0.33BaTiO(3) (BF-BT) films and the performance of bulk acoustic wave (BAW) resonators is analyzed using test structures with the BF-BT films grown at different positions relative to the plume axis in the pulsed laser deposition system. The BF-BT film grain size and surface roughness reveal a strong asymmetric surface distribution and decrease significantly in the film region facing the laser beam-plume interaction area. The (100) BF-BT texturing is enhanced in this film region. The variations in the BF-BT film microstructure result in corresponding variations of the BAW resonator performance. Their correlations are established using the model of the roughness induced attenuation of the reflected acoustic waves and theory of the dc field induced piezoelectric effect. The BAW resonators with the highest parameters are obtained in the BF-BT film region facing the laser beam-plume interaction area. The BAW resonators located in this film region reveal a mechanical Q-factor of 200 at 4.2GHz, an effective electromechanical coupling coefficient of 10% and a tunability of the series resonance frequency of 4.5%.