1. Department
of Nanofusion Technology, Pusan National University, 30 Jangjeon-dong, Geumjung-gu, Busan 609-735, South Korea
2. Department
of Nanomechatronics Engineering, Pusan National University, 30 Jangjeon-dong, Geumjung-gu, Busan 609-735, South Korea
3. School
of Mechanical and Aerospace Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, South Korea
4. DRAM
Design Team, Memory Division, Samsung Electronics, Hwasung-City, Gyeonggi-do, South Korea