Controlled elaboration of high aspect ratio cone-shape pore arrays in silicon by metal assisted chemical etching

Abstract : Metal Assisted Chemical Etching (MACE) of Si has attracted the attention of academy and industry during the last decades as an efficient low-cost wet etching method to produce Si nanostructures with high aspect ratios (HAR) that can find applications in various fields (e.g. optoelectronics).Several noble metals are known to be effective catalysts for MACE: Ag nanoparticles (NPs) or networks, provide an extremely localized etching with the formation of mesopores or Si nanowire arrays. On the contrary, MACE with Pt NPs is delocalized, resulting in the formation of cone-shaped pores whose formation mechanism and potential applicationshave received less attention. In this work, MACE with Pt NPs under an applied external bias is presented as a novel approach to synthesize HAR Si nanostructures of controlled size and shape, with clear application as builtin blocks for photovoltaic devices, their reflectivity being less than 3 % vs. ~10 % for the most efficient standard texturization technique (inverted pyramids). Combination of voltammetry, impedance spectroscopy andband bending modelling simulations allowa thorough physicochemical characterization of this MACE process. Because such morphologies are difficult to obtain even with advanced plasma etching techniques, MACE with Pt has a strong potential for Si surface structuration.