1. Samsung Advanced Institute of Technology; Samsung Electronics; Suwon 443-803 South Korea
2. Department of Materials Science and Engineering; Frederick Seitz Materials Research Laboratory; University of Illinois at Urbana-Champaign; Urbana Illinois 61801 USA
3. Department of Materials Science and Engineering; Seoul National University; Seoul 151-744 South Korea
4. College of Nanoscience and Nanotechnology; Pusan National University; Busan 609-735 South Korea