Semiconductor metalattices consisting of a linked network of 3D nanostructures with periodicities on length scales <100nm can enable tailored functional properties due to their complex nanostructuring. For example, by controlling both the porosity and pore size, thermal transport in these phononic metalattices can be tuned—making them promising candidates for efficient thermoelectrics or thermal rectifiers. Thus, the ability to characterize the porosity, and other physical properties, of metalattices is critical but challenging, due to their nanoscale structure and thickness. To date, only metalattices with high porosities, close to the close-packing fraction of hard spheres, have been studied experimentally. Recently, a STROBE team characterized the porosity, thickness, and elastic properties of a low-porosity, empty-pore silicon metalattices for the first time. Laser-driven nanoscale surface acoustic waves were probed by EUV scatterometry to nondestructively measure the acoustic dispersion in these thin silicon metalattice layers. The Young’s modulus, porosity and metalattice layer thickness were then extracted. These advanced characterization techniques are critical for informed and iterative fabrication of energy-efficient devices based on nanostructured metamaterials.
