1. Harvard
John A. Paulson School of Engineering and Applied Sciences, Harvard University, 9 Oxford Street, McKay 125, Cambridge, Massachusetts 02138, United States
2. CNR-SPIN
U.O.S. Napoli, Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant’Angelo, Via Cintia, 80126 - Napoli, Italy
3. Centre
de Recherche sur l’Hétéro-Epitaxie et ses Application, CNRS, Rue Bernard Gregory, Sophia-Antipolis, 06560 Valbonne, France