1. Shanghai Institute of Ceramics, Chinese Academy of Sciences, 585 He-shuo Road, Shanghai 201899, P.R. China
2. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
3. Institute of Physics of the Czech Academy of Sciences, Cukrovarnicka 10/112, Prague 16200, Czech Republic
4. Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Brehova 7, Brehova 11519, Czech Republic
5. Faculty of Biomedical Engineering, Czech Technical University in Prague, Náměstí Sítná 3105, 272 01 Kladno, Czech Republic