1. School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
2. Metallic Materials Development Department, TANAKA KIKINZOKU KOGYO K.K., Isehara Technical Center, 28 Suzukawa, Isehara, Kanagawa 259-1146, Japan
3. Chemical Materials Development Department, TANAKA KIKINZOKU KOGYO K.K., Tsukuba Technical Center, 22 Wadai, Tsukuba, Ibaraki 300-4247, Japan