1. Fraunhofer IPMS, Center Nanoelectronic Technologies, 01109 Dresden, Germany
2. Advanced Thin Film Technology Group, Institute of Materials Science, TU Darmstadt, 64287 Darmstadt, Germany
3. Materials Research Department, GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany and Institute of Materials Science, TU Darmstadt, 64287 Darmstadt, Germany