1. Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 05006, Republic of Korea
2. School of Electrical Engineering, Korea University, Seoul 02841, Republic of Korea
3. Department of Electrical Engineering, Sejong University, Seoul 05006, Republic of Korea
4. Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi, Vietnam
5. Division of Physics and Semiconductor Science, Dongguk University, Seoul 04620, Republic of Korea