JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 49, page. 692 - 695, 2006-12
ADVANCED FUNCTIONAL MATERIALS, vol. 19, no. 15, page. 2398 - 2406, 2009-08-10
PHYSICAL REVIEW B, vol. 76, no. 3, page. 35316 - 35316, 2007-07