1. Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
2. Technische Universität München, Electrical Engineering and Information Tech., Arcisstr. 21, 80333 München, Germany
3. Consiglio Nazionale delle Ricerche, ISMN, Via Salaria km 29.6, 00017 Monterotondo (Rome), Italy