Nondestructive probing of the transport and elastic properties of nanostructured metalattices using coherent EUV beams

Nanoscale metamaterials exhibit engineered thermal, magnetic, and electronic properties, which are essential for nanoelectronics, thermoelectrics, and ultralight media. Nanostructured metalattices are artificial 3D solids, periodic on length scales 1-100nm, that enable the functional properties of materials to be tuned. However, characterizing such materials is extremely challenging. Here we overcome this challenge by using tabletop high harmonic extreme ultraviolet (EUV) beams, with wavelengths (≈30nm) and pulse durations (≈10fs) that are well-matched for probing nanoscale structure and function. We demonstrate nondestructive measurements of the mechanical, structural, and transport properties of complex 3D nanostructured media—specifically in metalattices made from 14-30nm silica nanosphere templates infiltrated with silicon. We extract the mechanical and structural properties from the measured acoustic dispersion, which agrees with continuum models. In contrast, the heat flow through the metalattices deviates from macroscopic models due to the nanoscale structure. These samples have not only a lower thermal conductivity than expected, but also exhibit transport properties that depend on the heat source geometry. We support these findings with advanced atomistic models.