Implications of the HF/H2O2 effect on the electrochemical etching formation of macroporous silicon at various etching times

This study presents the development of macroporous silicon (MPS) structures via electrochemical anodization of unpolished p-type silicon in hydrofluoric acid (HF)-based solutions containing hydrogen peroxide (H₂O₂) and ethanol (C₂H₅OH). The process was conducted without external illumination and under the effect of various etching durations. MPS networks are materials that are ideally suited for tubular structures at the micrometer scale. The incorporation of H₂O₂ into its formation enhances the oxidation rate and facilitates the production of more well-defined pore structures. The resulting MPS layers were characterized using scanning electron microscopy (SEM) and ultraviolet–visible (UV–Vis) spectrophotometry. SEM images revealed the formation of various structures, including deep pores, tree-like features, cracks, islands, and spongy networks. The pore sizes ranged from 0.43 to 2 microns, with pore depths reaching around 6.4 microns into the bulk silicon. Optical studies showed that the addition of H₂O₂ significantly altered the photoluminescence (PL) emission intensity highlighting changes in the material’s recombination efficiency.