1. Department of Physics, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul03760, Republic of Korea
2. Department of Computer Science and Engineering, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul03760, Republic of Korea
3. Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, Delft2628 CJ, The Netherlands
4. Logic Technology Development Quality and Reliability, Intel Corporation, Hillsboro, Oregon97124, United States