1. Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
2. State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
3. Graduate Institute of Precision Engineering, National Chung Hsing University, Taichung 402, Taiwan
4. Innovation and Development Center of Sustainable Agriculture, National Chung Hsing University, Taichung 402, Taiwan
5. EM Application Department of EM Business Unit, JEOL Ltd., 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan
6. Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
7. Institute of Physics, Academia Sinica, Taipei 115, Taiwan