1. Department of Applied Physics, Institute of Natural Sciences, and Integrated Education Institute for Frontier Science and Technology, Kyung Hee University, Yongin 17104, Republic of Korea
2. V-memory Corp. Heungdeok IT Valley B605, 13, Heungdeok 1-ro, Giheung-gu, Yongin-si, Gyeonggi-do, Republic of Korea