1. National Key Laboratory of Electronic Films and Integrated Devices, School of Integrated Circuit Science and Engineering, University of Electronic Science and Technology of China, 611731 Chengdu, P. R. China
2. Shenzhen Institute for Advanced Study, University of Electronic Science and Technology of China, 518110 Shenzhen, P. R. China
3. Dongguan Neutron Science Center, Dongguan 523803, P. R. China