[1] Natl Ctr Nanosci & Technol, CAS Ctr Excellence Nanosci, Beijing 100190, Peoples R China
[2] Natl Ctr Nanosci & Technol, CAS Key Lab Standardizat & Measurement Nanotechno, Beijing 100190, Peoples R China
[3] Nanyang Technol Univ, Sch Phys & Math Sci, Div Phys & Appl Phys, Singapore 637371, Singapore
[4] Nanyang Technol Univ, Sch Mat Sci & Engn, Ctr Programmable Mat, Singapore 639798, Singapore
[5] Zhejiang Univ, Sch Mat Sci & Engn, State Key Lab Silicon Mat, Hangzhou 310027, Zhejiang, Peoples R China
[6] Nanyang Technol Univ, Sch Elect & Elect Engn, Nanoelect Ctr Excellence, NOVITAS, Singapore 639798, Singapore
[7] Nanyang Technol Univ, Energy Res Inst NTU ERI N, 50 Nanyang Dr, Singapore 637553, Singapore