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-ass isted electrochemistry of n-type c-Si wafers immersed in HF/C2H5OH/H2O mixt ures of different proportions. Analysis of the PS by micro-Raman spectrosco py was undertaken simultaneously with micro-photoluminescence spectroscopy to enable correlation of the characteristics of the luminescence spectra wi th the probable emission structures. In addition, the cross-sectional surfa ces of the samples were studied by micro-Raman and micro-photoIuminescence spectroscopy to compare the luminescence of the structures present in the b ulk of the PS with that of the structures of the top surface. The results s uggest that the strong luminescence observed in these PS films originates f rom structures present in the bulk of the PS, and not from surface structur es. Morphological data obtained by scanning electron microscopy (SEM) and a tomic force microscopy (AFM) are also discussed. (C) 2000 Elsevier Science B.V. All rights reserved.