1. Department of Electrical and Computer Engineering Sungkyunkwan University (SKKU) Suwon 16419 Korea
2. Department of Semiconductor and Display Engineering Sungkyunkwan University Suwon 16417 Korea
3. Memory Technology Design Team Samsung Electronics Co. Ltd Hwasung 18448 Korea
4. Research Laboratory of Electronics Massachusetts Institute of Technology (MIT) Cambridge MA 02139 USA
5. School of Advanced Materials Science and Engineering Sungkyunkwan University Suwon 16417 Korea
6. School of Semiconductor Science & Technology Jeonbuk National University Jeonju 54896 Korea
7. Sungkyunkwan Advanced Institute of Nanotechnology (SAINT) Sungkyunkwan University Suwon 16417 Korea