Influence of Elastic Properties of Thin Films deposited on Si and/or Mg substrates on Rayleigh velocity dispersion evolution

In this work, we present a quantitative investigation of dispersion curves of Rayleigh velocity, V R, in several loading layers/(Si, Mg) substrates. For every layer/substrate system, it is shown that as the thickness, h, increases the curves decrease with different slopes then saturate at variable transition normalized thickness, (h/λTL)tr. To quantify the transition phenomenon, we introduced a parameter, χ, depending on V R and densities, ρ, of both layers and substrates. Hence, it was possible to deduce analytical expressions of the form: (h/λTL)tr.=1.16+0.16χ for layers/Si systems and (h/λTL)tr.=0.37+0.65χ for layers/Mg combinations.