1. Institute
for Quantum Engineering
and Micro-Nano Energy Technology, Key Laboratory of Low-Dimensional
Materials and Application Technologies, and Faculty of Materials,
Optoelectronics, and Physics, Xiangtan University, Hunan 411105, China
2. School of Information and Electronic
Engineering, Hunan University of Science and Technology, Hunan 411105, China
3. School
of Electrical and Electronic
Engineering, Nanyang Technological University, Singapore 639798, Singapore