JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS, vol. 43, no. 8B, page. L1106 - L1108, 2004-08-15
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 45, no. 2, page. L252 - L255, 2004-08
CARBON, vol. 42, no. 10, page. 2073 - 2080, 2004-01