A Comparative Study of the Effectiveness of Porous, Pre-etched, and Activated Silicon Surfaces as SERS Sensors

New, easy, and less complicated formation pathways of silicon (Si) surface structures and the well-known photo-electrochemical etching process have been presented and investigated successfully. These pathways included the pre-etching and the activation processes. Significant arrays of silicon surface structures and topographies were achieved as porous, pre-etched, and activated surfaces. These structures have been used as substrates for the palladium nanoparticle (PdNP) deposition process. The investigations of the samples include structural and optical examinations. For porous silicon samples, the obtained field emission scanning electron microscope (FESEM) results showed large microscale pores with 0.387 µm average diameter and small nanoscale pores formed inside them with 21.61 nm average diameter. Such a porous nature affords a larger surface area within a compact volume, for the pre-etched silicon samples nanoscale pores were exhibited with an average pore diameter of 62.62 nm distributed evenly on the surface. Lastly, for the activated silicon samples; the once-smooth silicon surface displays a texture with a noticeable uneven appearance, microscopic irregularities, grooves, and scarped areas with an average roughness of 6.6 µm and root mean square of 12.853 µm. It is shown that surface-enhanced Raman spectroscopy of these structure-coated PdNP substrates could successfully detect nitrate at low concentrations. In particular, the pre-etched Si structure exhibited the highest enhancement factor of (1.79 × 10¹¹).