1. Department of ElectrophysicsNational Chiao Tung University Hsinchu 300 Taiwan
2. Department of PhysicsNational Chung Hsing University Taichung 40227 Taiwan
3. Department of Electrical Engineering and Institute of Electronic EngineeringNational Tsing Hua University Hsinchu 300 Taiwan
4. Department of Materials Science and EngineeringNational Chiao Tung University Hsinchu 300 Taiwan
5. Center for the Intelligent Semiconductor Nano‐system Technology ResearchNational Chiao Tung University Hsinchu 300 Taiwan
6. Institute of NanoscienceNational Chung Hsing University Taichung 40227 Taiwan