1. Key
Laboratory of Advanced Micro/Nano Functional Materials, School of
Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China
2. Department
of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong
3. Key
Laboratory of Optoelectronic Devices and Systems of Ministry of Education
and Guangdong Province, Shenzhen University, Shenzhen 518060, China