Surface acoustic wave bandgaps for conical pillars on a piezoelectric substrate

Abdelali Mrabti (1) , Mourad Oudich (1) , Abdellatif Akjouj (1) , Yan Pennec (1) , Bahram Djafari-Rouhani (1) , Abdelkrim Talbi (1) , Jérémy Streque (1) , Yu Du (1) , Ali Soltani (1) , Philippe Pernod (1)

1 IEMN - Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520

We report theoretically on the band structure of a square lattice phononic crystal made up of nickel (Ni) conical pillars deposited on the surface of a semi-infinite LiNbO3 substrate. Calculations have been performed with a 3D finite element method taking into account material anisotropy and piezoelectricity of the LiNbO3. We demonstrate the existence of wide surface acoustic wave (SAW) bandgaps determined from the band structure. The effects of pillar geometry on the existence of large surface acoustic bandgaps are investigated. The structure is realized experimentally and transmission and phase time curves show a good agreement with our theoretical calculation. We investigate further the effect of the geometrical parameters on the behavior of the lowest SAW bandgap, by changing the height h and radius r of the pillars as well as the angle  of the cone. When increasing h, the band gap frequency shifts downwards and slightly widens. The band gap can be significantly widened by decreasing the radius r. Finally, by increasing the angle  of the cone, the gap shifts downwards and increases its width.

Abdelali Mrabti, Mourad Oudich, Abdellatif Akjouj, Yan Pennec, Bahram Djafari-Rouhani, et al.. Surface acoustic wave bandgaps for conical pillars on a piezoelectric substrate. European Materials Research Society Spring Meeting, E-MRS Spring 2014, Symposium D - Phonons and fluctuations in low dimensional structures, 2014, Lille, France. ⟨hal-00962392⟩