Vapour-etching-based porous silicon: a new approach

We present a new approach of porous silicon (PS) formation using a vapour-etching (VE)-based technique.We detail the principle of the method and explain how PS layers (PSLs) form, taking into account all influencing preparation parameters.The structural properties of the obtained PSLs were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).The obtained results show clear evidence of the formation of a porous layer when Si substrates are submitted to VE.High-resolution SEM observations show that both p and p type PSLs are composed of small interconnected clusters with q sizes ranging from 20 to 50 nm.TEM observations reveal that these clusters are essentially composed of dot-like crystalline Si particles embedded in an amorphous phase with sizes not exceeding 5 nm.The photoluminescence (PL) of the PSLs was found to be related to the crystalline Si dots.It was found that PL emission occurs at high energies as compared to conventional techniques.The dependence of the PL spectra with some preparation parameters is also discussed. 2002 Elsevier Science B.V. All rights reserved.