1. State Key Laboratory of Electronic Thin Film and Integrated Devices School of Electronic Science and Engineering University of Electronic Science and Technology of China Chengdu 610054 P. R. China
2. College of Forestry and Landscape Architecture Key Laboratory of Energy Plants Resource and Utilization Ministry of Agriculture Key Laboratory of Biomass Energy of Guangdong Regular Higher Education Institutions South China Agricultural University Guangzhou Guangdong 510642 China
3. School of Materials Science and Engineering Zhengzhou University Zhengzhou 450002 P. R. China