1. Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstraße 20, D-01069 Dresden, Germany
2. Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, D-01062 Dresden, Germany
3. TU Bergakademie Freiberg, Institute of Applied Physics, Leipziger Str. 23, D-09596 Freiberg, Germany