[1] CNRS, Lab Photon & Nanostruct, Route Nozay, F-91460 Marcoussis, France
[2] Univ Tunis El Manar, Fac Sci Tunis, Unite Nanomat & Photon, Campus Univ, Tunis, Tunisia
[3] Synchrotron SOLEIL, BP48, F-91192 Gif Sur Yvette, France
[4] CNRS, Ctr Rech HeteroEpitaxie & Ses Applicat, Valbonne, France