1. CNR-INFM Laboratorio MDM, via C. Olivetti 2, 20041 Agrate Brianza (MI), Italy, Laboratory TREFLE, ENSAM Department of Mechanics, Esplanade des arts et métiers 33405 Talence Cedex, France, STMicroelectronics M6, via C. Olivetti 2, 20041 Agrate Brianza (MI), Italy, and Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Milano, Italy