Structural and photoluminescent properties of porous silicon with deep pores obtained by laser-assisted electrochemistry

Columnar porous silicon (PS) with deep pores has been prepared by laser-assisted electrochemistry of n-type c-Si wafers immersed in HF/C2H5OH/H2O mixtures of different proportions. Analysis of the PS by micro-Raman spectroscopy was undertaken simultaneously with micro-photoluminescence spectroscopy to enable correlation of the characteristics of the luminescence spectra with the probable emission structures. In addition, the cross-sectional surfaces of the samples were studied by micro-Raman and micro-photoluminescence spectroscopy to compare the luminescence of the structures present in the bulk of the PS with that of the structures of the top surface. The results suggest that the strong luminescence observed in these PS films originates from structures present in the bulk of the PS, and not from surface structures. Morphological data obtained by scanning electron microscopy (SEM) and atomic force microscopy (AFM) are also discussed.