1. UNIROUEN, INSA Rouen, CNRS, Groupe de Physique des Matériaux, Normandie Université, 76000 Rouen, France
2. CEMES-CNRS, 29 rue Jeanne Marvig, Toulouse, France
3. Ioffe Institute, 194021 St. Petersburg, Russia
4. Submicron Heterostructures for Microelectronics Research and Engineering Center RAS, 194021 St. Petersburg, Russia
5. Materials Department, University of California, Santa Barbara, California 93106, USA