Photoexcited Fano interaction in laser-etched silicon nanostructures

Photoexcitation dependent Raman studies on the optical phonon mode in silicon nanostructures (Si NS) prepared by laser-induced etching are done here. The increase in the asymmetry of the Raman spectra on the increasing laser power density is attributed to Fano interference between discrete optical phonons and continuum of electronic excitations in the few nanometer size nanoparticles made by laser-induced etching. No such changes are observed for the same laser power density in the crystalline silicon sample or ion-implanted silicon sample followed by laser annealing. A broad photoluminescence spectrum from Si NS contains multiple peak behavior, which reveals the presence of continuum of electronic states in the Si NS. (c) 2007 American Institute of Physics.