1. WPI Center for Materials Nanoarchitectonics
(MANA), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan
2. CEMES (Centre d’Elaboration des Matériaux et d’Etudes Structurales), CNRS B.P. 94347, 29 rue Jeanne Marvig, F-31055 Toulouse, France
3. Zurich Research Laboratory, IBM Research, CH-8803 Rüschlikon, Switzerland
4. Japan PRESTO and CREST, JST, Kawaguchi, Saitama 332-0012, Japan