1. Nanotechnology Research Laboratory, Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh
2. Department of Mechanical Science and Bioengineering, Osaka University, Osaka 560-8531, Japan
3. Institute of Multidisciplinary Research of Advanced Materials, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980-0877, Japan