1. Department of Materials Science and Engineering and Inter-University Semiconductor Research Center Seoul National University Gwanak-ro 1, Gwanak-gu Seoul 08826 Republic of Korea
2. Graduate School of Engineering Practice Seoul National University Gwanak-ro 1, Gwanak-gu Seoul 08826 Republic of Korea
3. Department of Electrical Engineering Myongji University 116 Myongji-ro, Cheoin-gu, Yongin-si Gyeonggi-do 17058 Republic of Korea