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Abstract: Silicon nanoparticles/nanostructures have been prepared by different methods. Lasers of different operational modes have been employed to prepare silicon nanoparticles by laser-induced etching, laser ablation and laser annealing. Moreover, electrochemical and photoelectrochemical etching were performed to synthesize silicon nanostructures. Optimum etching rate of 2.4 µm/min is obtained for the porous layer prepared by electrochemical etching under optimum conditions of 15 mA/cm 2 and 10 minutes etching current density and etching time, respectively. Characterization of the prepared silicon nanostructures / nanoparticles was carried out using various methods. The experimentally observed Raman spectra of nano-structured layers prepared by three etching techniques reveal a red shift to 518 c