Porous silicon (PSi) was formed by an electrochemical etching of crystalline silicon substrates irradiated with silver (Ag) ion beam with energy of 1.25 MeV. Micro-Raman scattering results reveal that the irradiation process induces amorphization in the silicon substrate. Scanning electron microscopy, energy dispersive X-ray spectroscopy and micro-Raman scattering results show that the irradiation process induces important morphological and structural modifications in the PSi layer. The irradiation process leads to a considerable enhancement in the etching rate, a significant increase in the O/Si ratio and a reduction in the average size of the silicon nano-crystallites (nc-Si) from ∼7.76 nm to ∼2.26 nm in the skeleton of the PSi layer. These changes resulted in an important modification of photoluminescence (PL) properties of the PSi layer. Additional PL peak associated with the ‘F-band’ of the PSi was de-convoluted in the PL spectrum of the PSi layer formed on the irradiated silicon substrate.