1. Department of Materials Science and Engineering National Yang Ming Chiao Tung University No.1001, University Rd., East Dist. Hsinchu City 30010 Taiwan
2. Department of Physics National Chung Hsing University Taichung 402 Taiwan
3. Center for the Intelligent Semiconductor Nano‐system Technology Research National Yang Ming Chiao Tung University No.1001, University Rd., East Dist. Hsinchu City 30010 Taiwan