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In this work, we investigate numerically the propagation of Lamb waves in a film bulk acoustic resonator (FBAR) structure formed by piezoelectric ZnO layer sandwiched between two Mo electrodes coupled with Bragg reflectors; the system is thus considered as a phononic-crystal (PnC) plate. The aim is to suppress the first-order symmetric Lamb wave mode considered as a spurious mode caused by the establishment of a lateral standing wave due to the reflection at the embedded lateral extremities of the structure; this spurious mode is superposing to the main longitudinal mode resonance of the FBAR. The finite element study, using harmonic and eigen-frequency analyses, is performed on the section of FBAR structure coupled with the PnC. In the presence of PnC, the simulation results show the evidence of a selective band gap where the parasitic mode is prohibited. The quality factor of the FBAR is enhanced by the introduction of the PnC. Indeed, the resonance and antiresonance frequencies passed from 1000 and 980 (without PnC) to 2350 and 1230 (with PnC), respectively. This is accompanied by a decrease in the electromechanical coupling coefficient from 10.60% to 6.61%.

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In this paper, we investigate numerically the coupling of the Rayleigh mode with the micro-wall resonance modes in inter-digital transducers (IDTs) electrodes of surface acoustic wave (SAW) devices. We perform a finite element analysis (FEA) of the SAW features using an implemented model using COMSOL Multiphysics® software. The SAW structure comprises identical transmitter and receiver IDTs electrodes, with different electrode heights (he). The proposed FEA study is based on the extraction of reflection (S11) and transmission (S21) coefficients of the SAW device. The IDTs are considered to be a micro-wall phononic crystal acting as local resonators at frequencies inside the SAW passband. The locally resonance gap is strongly dependent on the he value, S11 and S21 parameters are affected by the SAW energy absorption in the IDTs system. We have chosen two he values (0.5 and 3 µm) to study low and high aspect ratios of micro-walls; corresponding respectively to Bragg-type and resonance-type bandgaps appearing near to the SAW central frequency. At the SAW resonance frequency, the return (S11) and the insertion (S21) losses are reduced. S21 is reduced by 12.73 and 18.49 dB for he=0.5 and 3 µm, respectively, accompanied by an increase in the quality factor, and S11 parameter is reduced by 1.357 and 4.98 dB for he=0.5 and 3 µm, respectively.

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Due to their outstanding physical and mechanical features, ZrN thin films are increasingly used as coatings to protect materials intended for nuclear applications such as Zirconium. To our knowledge, there is no report of pulsed laser deposition (PLD) of ZrN thin films on a Zr substrate. In this work, we have successfully prepared ZrN thin films on Zr substrates using the PLD technique with a KrF excimer laser, in a N2 environment at 2 Pa pressure and a fixed substrate temperature of 500 °C. The deposited 200 nm ZrN thin films exhibited a homogeneous surface and showed a face-centered cubic polycrystalline structure. The surface roughness was 3.69 nm. X-ray diffraction, Raman and X-ray photoelectron spectroscopy measurements confirmed the presence of ZrN. The coated sample's mean value of hardness (11.6 GP) doubled that of the uncoated sample.