Fig. 1: Nanostructured sample and EUV TG signal from a uniform (U) and a nanostructured (NS) SiN membrane.

a, b TEM image of the nanoporous SiN membrane. The spatial scale of 2 μm (a) and 0.5 μm (b) are indicated by the white segments. The conical shape (see Methods) of the holes can be perceived in the latter image, with the inner diameter of the hole appearing as a white circle. The square of dashed lines represents the unit cell of the pores lattice, with indicated the period A = 377 nm, the neck N = 253 nm and the diameter D = 124 nm. c–h The experimental waveforms (blue dots connected with lines) are reported as a function of Δt; the values of λ_ph = L_TG are reported in the individual panels. Red lines are best fits, which account for both thermal relaxation and a variable number of phonon modes (see the text). Notice that the range in Δt for the NS is much shorter than for the U.