1. Laboratory of Infrared Materials and Devices, The Research Institute of Advanced Technologies, Ningbo University, Ningbo, Zhejiang 315211, China
2. Key Laboratory of Photoelectric Detection Materials and Devices of Zhejiang Province, Ningbo, Zhejiang 315211, China
3. Leibniz Institute of Surface Engineering (IOM), Permoserstrasse 15, D-04318 Leipzig, Germany