1. Department of Mechanical Engineering and Advanced Institute of Manufacturing with High-tech Innovations, National Chung Cheng University, Chia-Yi County 62102, Taiwan
2. Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
3. Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Lavrentjeva 13, Novosibirsk 630090, Russia