1. School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
2. Research Center for Advanced Information Materials (CAIM), Huangpu Research and Graduate School of Guangzhou University, Guangzhou 510555, China
3. Key Lab of Si-based Information Materials & Devices and Integrated Circuits Design, Education Department of Guangdong Province, Guangzhou, Guangdong Province 510610, China