1. SEU-FEI Nano-Pico Center, Key Laboratory
of MEMS of Ministry of Education, School of Electrical Science and
Engineering, Southeast University, 210096 Nanjing, China
2. Laboratoire de Physico-Chimie des
Matériaux Luminescents, Université Claude Bernard Lyon
1, UMR 5620 CNRS−UCBL, 69622 Villeurbanne Cedex, France