APPLIED PHYSICS LETTERS, vol. 71, no. 18, page. 2656 - 2658, 1997-11-03
JOURNAL OF THE KOREAN PHYSICAL SOCIETY, vol. 30, page. S117 - S122, 1997-06
JOURNAL OF APPLIED PHYSICS, vol. 82, no. 10, page. 5011 - 5016, 1997-11-15