1. IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University 1 , 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea
2. Department of Electrical and Electronic Engineering, Jeonju University 2 , 303 Cheonjam-ro, Wansan-gu, Jeonju-si, Jeollabuk-do 55069, South Korea
3. Department of Electronic Engineering, Cheongju University 3 , 298 Daesung-ro, Cheongju 28503, South Korea