[1] Seoul Natl Univ, Natl Creat Res Ctr Oxide Nanocrystalline Mat, Seoul 151744, South Korea
[2] Seoul Natl Univ, Sch Chem & Biol Engn, Seoul 151744, South Korea
[3] Sungkyunkwan Univ, Dept Phys, Suwon 440746, South Korea
[4] Sungkyunkwan Univ, Inst Basic Sci, Suwon 440746, South Korea