Assisted dewetting of pure Ge nanostructures for Mie-resonant all-dielectric photonics

Dewetting instability in semiconductor thin films offers a powerful route to realize self-organized nanostructures. However, its optical potential remains unexploited, especially in high-index materials like germanium (Ge). Here, we present a comprehensive theoretical and experimental study of pure Ge films undergoing solid-state dewetting on SiO2 substrates, leading to the formation of dielectric nanoresonators with strong Mie resonances in the visible spectrum. By introducing geometrical constraints in Ge thin films via electron-beam lithography, we achieve deterministic control over the dewetting process, guiding the morphological evolution to yield uniform, shape-engineered nano-islands with higher aspect ratios. We also demonstrate how the dewetting process parameters, resulting in different sizes of the nanoresonators, influence the spectral position of the Mie resonances, offering tailored scattering properties. Our approach enables wafer-scale fabrication of Ge-based optical nanoresonators, representing the first, to the best of our knowledge, experimental demonstration of assisted dewetting in Ge for nanophotonic applications. This bottom-up method opens a scalable and versatile platform for next-generation photonic devices, positioning dewetted Ge nanostructures as an innovative platform for all-dielectric light management in photonic applications.