[1] Pusan Natl Univ, Res Ctr Dielect & Adv Matter Phys, Pusan 609735, South Korea
[2] Pusan Natl Univ, Dept Phys, Pusan 609735, South Korea
[3] Nextron Corp, Pusan 609735, South Korea
[4] Gwangju Inst Sci & Technol, Dept Mat Sci & Engn, Kwangju 500712, South Korea