Porous Si formation and study of its structural and vibrational properties

In situ current (I)-(V) voltage studies were carried out to get a better understanding of the mechanism of formation of porous silicon (PS). It is observed that on decreasing the anodization current density below a critical value (similar to 75 mA cm(-2)) the size of the PS crystallites increases while for its values above 75 mA cm(-2) electropolishing occurs. Raman spectroscopic studies show that the sizes of the Si crystallites are small and change from 4.7 to 3.8 nm when the current densities are increased from 20 to 50 mA cm(-2). Transmission electron micrographs show preferential propagation of pores whereas transmission electron diffraction (TED) patterns show typical crystalline Si with the cubic structure. (C) 2002 Elsevier Science B.V. All rights reserved.