1. Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP); Technische Universität Dresden; Nöthnitzer Str. 61 01187 Dresden Germany
2. Department of Materials Science and Engineering; Northwestern University; Evanston IL 60208 USA
3. Institute for Materials Research (IMO-IMOMEC); Hasselt University; Wetenschapspark 1 BE-3590 Diepenbeek Belgium