NONLINEAR REFRACTIVE INDEX OF SILICON NANOSTRUCTURE PRODUCED BY PHOTO - ELECTROCHEMICAL ETCHING

Self - phase modulated optical fringe pattern are used to study the nonlinear optical response of nanocrystalline silicon produced by photoelectron chemical etching. Irradiation time - dependent changes in the refractive index are calculated for various sizes of nanocrystallites. Fabrication of porous silicon contains silicon nano - structures has been ca rried out via process PECE on n - type Si wafer with >100< orientation and electrolyte solution contain Hydrofluoric acid HF concentrations of (25% HF), various laser wavelengths (532nmand442nm). The observed morphological changes using scanning electron mic roscopy reveals formation of silicon nanostructure. There is a strong correlation between the nonlinear optical phenomenon of silicon nanocrystallites and the nanocrystallites size distribution.