1. Laboratoire de Physique des Interfaces et des Couches Minces, Ecole Polytechnique, 91128, Palaiseau, France
2. Carbon Nanotube Research Laboratory, Department of Physics, Center for Nanotubes and Nanostructured Composites, Sungkyunkwan Advanced Institute of Nanotechnology, Sungkyunkwan University, 440-746, Suwon, Korea