1. Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
2. Research & Development Process Team, SK Hynixinc., Icheon-si 17336, Republic of Korea
3. School of Advanced Material Science & Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
4. Process Development Team, Semiconductor R&D Center, Samsung, Hwaseong-si 18448, Republic of Korea
5. Pohang Accelerator Laboratory, POSTECH, Pohang 790-784, Republic of Korea