Metal-Assisted Chemical Etching Using Tollen’s Reagent to Deposit Silver Nanoparticle Catalysts for Fabrication of Quasi-ordered Silicon Micro/Nanostructures

Metal-assisted chemical etching (MacEtch) of semiconductor materials in HF/H2O2 solution using noble-metal particles as catalysts has gained much attention in the past few years due to its unique properties. In this work, nanoscale Ag particles were deposited on (100) and (111) surfaces of polished p-Si wafers through the silver-mirror reaction. Subsequently these wafers were etched in 1:1:1 (v:v:v) HF(49%):H2O2(30%):EtOH solution at ambient temperature and pressure for 12 h, producing a number of different quasi-ordered silicon micro/nanostructures. The resulting surface-modified wafers exhibited mixed micro- and nanostructures that are an inherent feature of the etch process; for example, steps appear on the sidewalls of crystallographically defined nanopores, because the catalytic Ag nanoparticles are convected as they transit the developing pore during the etching process. The resulting materials exhibited much reduced reflectivity, reaching a maximum of 3.7× reduction near 330 nm, which renders them of interest in potential applications such as back-reflector templates for deposition of thin-film solar cell materials.