1. Division of Optical Spectroscopy, Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wrocław, 50-422, Poland.
2. Graphene Energy, Ltd., Wrocław, 50-422, Poland.
3. BCMaterials, Basque Center for Materials, Applications and Nanostructures, Leioa, 48940, Spain.
4. Institute of Solid State Physics, University of Latvia, Riga, LV-1063, Latvia.
5. Department of Physics & CICECO−Aveiro Institute of Materials, University of Aveiro, Aveiro, 3810-193, Portugal.