1. Department of Electrical Engineering, Chosun University, 309, Pilmun-daero, Dong-gu, Gwangju 61452, Republic of Korea
2. School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, AZ 85287, USA
3. Department of Nanotechnology Engineering, Pukyong National University, 45, Yongso-ro, Nam-gu, Busan 48547, Republic of Korea