“…The first stage involved chemical (immersion) deposition of copper into the subsurface layer from an aqueous solution containing 0.03 M CuSO 4 and 0.14 M HF for 3 min. This results in silicon's chemical dissolution and displacement of its atoms with those of copper [22] . In the case of porous silicon, this process is generally contained in its subsurface area due to significant diffusion limitations, as well as the presence of large amounts of structural defects, and the rest of the layer remains mostly intact.…”