The effect of Ti, W, Ag and TiO₂ particles on the structural and optical properties of porous silicon obtained in various electrolytes

This study explores the enhancement of porous silicon (PS) surfaces through surface modification with titanium dioxide (TiO₂), silver (Ag), titanium (Ti), and tungsten (W) nanoparticles using the magnetron sputtering technique. PS samples were initially fabricated via electrochemical etching of crystalline silicon, employing two different electrolytes: hydrofluoric acid (HF) and hexafluorosilicic acid (H₂SiF₆). The structural and optical properties of these samples were meticulously analyzed using Raman spectroscopy, reflectance spectroscopy, and scanning electron microscopy (SEM). The results revealed that surface modification with metal nanoparticles and metal oxides led to significant modifications in near-surface structural order, evidenced by shifts in Raman spectra towards higher frequencies. These shifts are attributed to local near-surface crystalline modifications rather than bulk crystallinity changes. Photoluminescence (PL) measurements demonstrated noticeable changes in intensity and peak shifts, suggesting alterations in the energy levels and structural composition of the PS. Reflectance spectra exhibited interference patterns and variations in material transparency, which were dependent on the type of nanoparticles and thickness of the deposited nanoparticle layer. Moreover, the choice of electrolyte was found to play a crucial role in determining the porosity and optical characteristics of the PS, with the alternative H₂SiF₆ electrolyte producing distinct structural and optical effects compared to the traditional HF electrolyte. These findings highlight the significant impact of nanoparticle surface modification and electrolyte selection on tailoring the properties of PS, offering new pathways for optimizing its use in photonics, electronics, and catalytic applications.