Fig. 2: Experimental and calculated phonon frequencies.
From: The effect of echoes interference on phonon attenuation in a nanophononic membrane
The values of ν, as extracted from the best fit of experimental data through Eq. (1), are reported as a function of k = 2π/λph for the uniform membrane in (a) and the nanostructured one in (b), together with the dispersions for symmetric Lamb waves calculated for a uniform membrane, using a Young modulus of 227.5 GPa, a Poisson ratio of 0.27 and a reduced average density ρNP = 2.653 g/cm3 for the nanostructured material (thick solid lines in (a) and (b)). Thin lines in (b) are calculated by using a Young modulus of 210 GPa. Symbols identify the phonon branch for experimental data: blue circles for the S2 branch, red squares for S3, while stars are the phonon modes of the nanostructure that have no counterparts in the uniform sample. Error bars come from the fit uncertainties. The black dotted line in (a) is the longitudinal phonon acoustic dispersion expected in a bulk sample.
