1. Department of Materials Science and Engineering, Yunnan University, 650091 Kunming, People’s Republic of China
2. Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany
3. Division of Materials Physics, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia