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, and 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 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.

Bismuth ferrite (BiFeO₃, abbreviated as BFO) has great potential for environmental applications

ZnO nanofibers were synthesized via a hydrothermal method. A single nanofiber was delicately transferred and deposited onto a TiNx thin film on a silicon substrate to facilitate the investigation of its piezotronic properties. An aluminum-coated atomic force microscope tip was employed in contact mode as a top nanoscale electrode to locally induce bending deformation in the individual ZnO nanofiber. The current–voltage (I–V) characteristics recorded between the top atomic force microscope tip electrode and the bottom TiNx surface exhibited rectifying behavior, indicative of the formation of a Schottky junction upon the application of a minimum bending force of 25 nN by the atomic force microscope tip. This force threshold was necessary to ensure adequate contact between the atomic force microscope probe and the ZnO nanofiber. However, upon exceeding the 25 nN bending force perpendicular to the c-axis, the forward current underwent a substantial reduction, eventually leading to complete suppression of the Schottky junction under further increments in the bending force. Finite element method simulations elucidated the presence of piezoelectric activity within the ZnO nanofiber, which was responsible for the observed attenuation in the forward current. The Cheung–Cheung method was employed to quantify the increase in barrier height at the Schottky junction as a function of the applied bending force.