1. Department of Physics and Energy Harvest Storage Research Center; University of Ulsan; Ulsan 44610 S. Korea
2. Department of Physics, Applied Physics and Astronomy; Binghamton University; Binghamton New York 13902 USA
3. Department of Physics; Chung-Ang University; Seoul 06794 S. Korea
4. School of Mechanical Engineering; University of Ulsan; Ulsan 44610 S. Korea
5. Electronics, Communication & Semiconductor Applications Department; Ulsan College; Ulsan 44610 S. Korea