Hemon, S. and Akjouj, A. and Soltani, A. and Pennec, Y. and El Hassouani, Y. and Talbi, A. and Mortet, V. and Djafari-Rouhani, B. (2014) Hypersonic band gap in an AlN-TiN bilayer phononic crystal slab. Applied Physics Letters, 104 (6).

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We show both theoretically and experimentally the existence of a complete band gap in a phononic crystal (PnC) constituted by periodical air holes drilled in a solid bi-layer slab. The composite slab is formed with an aluminum nitride (AlN) layer deposited on a titanium nitride (TiN) thin metallic film. Indeed, AlN slabs are of great interest in many technological applications, in particular, owing to the capabilities of AlN as a complementary metal-oxide-semiconductor compatible material for integration in piezoelectric radio frequency filters (thin-film bulk acoustic resonator technology). The TiN layer was chosen as a buffer to enable small lattice mismatch with AlN, thus resulting in highly c-axis oriented and low stresses at the interface. We calculate the band structure of the crystal by using a finite element method and discuss the frequency and width of the band gap as a function of the thicknesses of both layers and the shape of the holes, i.e., from cylindrical to conical. The introduction of the TiN slab contributes to slowly widen the band gap. The band gap narrows when the holes become conical and closes when the radius of one face in the cone exceeds by 15 the radius of the other face. Experimentally, the measurement of the elastic wave transmission through eight rows of the bi-layer PnC shows a band gap around 950MHz with an attenuation higher than 20dB. The experimental results are well reproduced by the simulations provided the conical shape of the air inclusions is taken into account. © 2014 AIP Publishing LLC.

Item Type: Article
Uncontrolled Keywords: Acoustic resonators; Aluminum coatings; Aluminum nitride; Balloons; Crystal structure; Elastic waves; Finite element method; Lattice mismatch; Metals; MOS devices; Nitrides; Phonons; Titanium compounds; Titanium nitride; Wave transmission, Aluminum nitride (AlN); Complementary metal-oxide-semiconductor compatible; Complete band gap; Phononic crystals (PnC); Radio frequency filters; Technological applications; Thin film bulk acoustic resonator; Thin metallic films, Energy gap
Subjects: Physics and Astronomy
Divisions: SCIENTIFIC PRODUCTION > Physics and Astronomy
Depositing User: Administrateur Eprints Administrateur Eprints
Last Modified: 31 Jan 2020 15:49
URI: http://eprints.umi.ac.ma/id/eprint/4489

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