* Corresponding author. Fax: #216-3-500-278; e-mail: has- sen.maaref@fsm.rnu.tn. Journal of Luminescence 80 (1999) 387—390 Optical properties of neodymium incorporated in porous silicon R. M’ghaı¨eth*, J.C. Vial, M. Haouari, H. Maaˆref  Laboratoire de Physique des Semi-conducteurs, Faculte & des Sciences de Monastir, Route de l+environnement 5000, Monastir, Tunisia  Laboratoire de Spectrome & trie Physique, Universite & Joseph Fourier-Grenoble I, BP 87, 38402 St Martin d+He % res Cedex, France Abstract We report the optical properties of Nd-incorporated porous silicon. Photoluminescence and photoluminescence excitation measurements have been performed. Room temperature emission spectra from dried or annealed samples have been studied. While steady-state photoluminescence results indicate porous silicon light absorption by the Nd, the photoluminescence excitation shows a deficiency of energy transfer between porous silicon and Nd ions.  1999 Elsevier Science B.V. All rights reserved. Keywords: Porous silicon; Incorporation; Nd; Annealing; Photoluminescence excitation 1. Introduction Semiconductor nanostructures are now of worldwide interest due to their potential applica- tion in electronic and optoelectronic device fabrica- tion. Significant scientific interest to porous silicon is attracted above all by the detection of its bright photoluminescence in the visible spectral region because of the band gap widening [1]. For our purpose, the morphology and the developed sur- face area of porous silicon (200—400 m/cm) are main considerations for the porous silicon rare earth (RE) doping. Because of their localized energy levels, RE elements are interesting candidates for doping. It is important to note, however, that the photoluminescence properties of RE-doped semi- conductors depend on the incorporation technique of RE impurities in the host material. For crystal- line semiconductors, the implantation, ion-assisted deposition or the thermal diffusion are well used techniques. Some groups attempted the introduc- ing of RE ions in porous silicon by a so-called “electrochemical method” and adapted thermal treatments for activation of RE ions [2]. This paper reports the results of photolumines- cence studies on neodymium incorporated in por- ous silicon. The main result is that the dispersion of RE ions is an active parameter in the establishment of the luminescence and no efficient energy transfer was observed. 2. Experimental We have studied porous silicon (p-Si) samples, prepared by anodization of polished (100) p-type silicon wafers (5—9  cm). The wafer was electro- chemically anodized using a mixture of HF (49%) 0022-2313/99/$ — see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 2 3 1 3 ( 9 8 ) 0 0 1 3 4 - 3