Structural and Optical Properties of Textured Silicon Substrates by Three-Step Chemical Etching.

We implemented the fabrication of hybrid structures, including pyramids, etching holes, and inverted pyramidal cavities on silicon substrates, by three-step chemical etching. To achieve this, we utilized anisotropic wet etching as the first-step etching to form pyramids of various sizes. Subsequently, metal-assisted chemical etching was performed to develop aligned etching holes on the pyramidal structure. Ultimately, anisotropic wet etching was used again as the third-step etching for the etchant to penetrate holes to form inverted pyramidal cavities. Optimizing the three-step etching treatments, large-scale textured structures with low reflectance could be obtained, and they show potential for applications in sensors, solar cells, photovoltaics, and surface-enhanced Raman scattering (SERS). Examples of using the textured silicon substrates for SERS applications were given.