Détermination expérimentale des courbes de dispersion des Ondes Acoustiques de Surface (SAW) se propageant dans des multicouches métalliques déposées sur substrat de silicium

International audienceL’ étude présentée consiste à déterminer les courbes de dispersion des modes de Rayleigh se propageant dans des multicouches Ni/Cu et Ni/CST/Cu déposées sur silicium pour deux orientations cristallographiques (100) et (111). Les modes de Rayleigh sont excités par un laser impulsionnel subnanoseconde et détectés par une sonde laser interférométrique. Les courbes de dispersion mesurées sont comparées aux courbes calculées à partir du formalisme de Stroh. Une technique d’estimation de l’épaisseur des multicouches est également proposée

Acousto-elastic theory for the coupling parameters in terms of nonlinear elastic, piezoelectric, electrostrictive, and dielectric constants in trigonal and hexagonal crystalline systems: applied in the crystal and solid-state physics

The aim of the acousto-elastic theory was to measure ultrasonic velocity changes which characterize the mechanical nonlinearity of a prestressed material. In this context, our purpose is to tabulate the invariant third-order elastic coefficients including the piezoelectric, electrostrictive, and dielectric corrections. The investigation is limited to trigonal and hexagonal crystalline structures, which represent the most often encountered symmetry classes for the piezoelectric materials. In fact, the enumeration includes the high-order tensors involved in the analysis of nonlinear behaviors associated with various electromechanical coupling forms. The obtained results are extensions to previous calculations in this area which bring some corrections to certain published combinations related to the invariance rules. The numerical procedure built using the software MATLAB is based on coordinate system transformations performed on the eigenbasis of their corresponding symmetry axes three- and sixfold. In this purpose, we found some contradictions between our results and a former paper published in Journal of Applied Physics. To the authors' knowledge, rechecking of the relationships between the invariant third-order constants and comparison with this last reference has not been discussed yet. The relationships between the invariant third-order coefficients presented in this work provide a number of attractive properties for use in mechanical and physical applications