1. Center for Electronic Materials; Korea Institute of Science and Technology; 5 Hwarang-ro 14-gil Seongbuk-gu Seoul 02792 Republic of Korea
2. Division of Materials Science and Engineering; Hanyang University; 222, Wangsimni-ro Seongdong-gu Seoul 04763 South Korea
3. Department of Materials Science and Engineering; and Inter-University Semiconductor Research Center; College of Engineering; Seoul National University; Seoul 151-744 Republic of Korea