Self-Sustained Quasi-1D Silicon Nanostructures for Thermoelectric Applications

Silicon (Si) nanowires have garnered significant interest for their potential applications in Si-based thermoelectrics, primarily due to their low thermal conductivity. While there are several methods to obtain Si nanowires, their density has been a limiting factor, resulting in a low power density that can be achieved by thermoelectric generators. To address this limitation, metal-assisted chemical etching (MACE) has been developed, enabling the creation of high-density nanopillar “forests”. This technique overcomes the previous density constraints. However, Si nanopillars protrude from a bulk Si wafer, which adds its thermal and electric resistivity to those of nanopillars, ultimately reducing the overall power density that can be attained. In this paper, we demonstrate how precise control of pre- and post-MACE processing allows for the creation of fully self-sustained quasi-1D Si nanostructures. We additionally demonstrate that pre-MACE Si processing does not control nanopillar bundling; rather, it primarily determines their shape. This outcome is attributed to the formation of gas nanobubbles during the initial steps of MACE.