1. MIND-Departament of Electronic and Biomedial Engineering, ‡Institute of Nanoscience
and Nanotechnology (IN2UB), and §DIOPMA, Departament de Ciència
de Materials i Química Física, Universitat de Barcelona, c/Martí i Franquès 1, E-08028 Barcelona, Spain
2. Institute of Semiconductor Technology and Laboratory for Emerging Nanometrology
LENA, Braunschweig University of Technology, 38106 Braunschweig, Germany