1. NanoSydMads Clausen InstituteUniversity of Southern Denmark Alsion 2 DK-6400 Sønderborg Denmark
2. Energy and Semiconductor Research LaboratoryInstitute of PhysicsUniversity of Oldenburg Carl-von-Ossietzky-Str. 9-11 D-26129 Oldenburg Germany
3. Kekulé-Institute for Organic Chemistry and BiochemistryUniversity of Bonn Gerhard-Domagk-Str. 1 D-53121 Bonn Germany