[1] Chonbuk Natl Univ, Nanomat Res Ctr, Chonju 561756, South Korea
[2] Chonbuk Natl Univ, Sch Chem Engn & Technol, Chonju 561756, South Korea
[3] Chonbuk Natl Univ, Dept Semicond Sci Technol, Chonju 561756, South Korea
[4] FED Project Team, Adv Inst Technol, Suwon 440600, South Korea