1. Department of Physics; Incheon National University; Incheon 406-772 Republic of Korea
2. Department of Polymer Science and Engineering; Inha University; Incheon 402-751 Republic of Korea
3. Department of Chemical Engineering; Kangwon National University; Samcheok 245-711 Republic of Korea
4. Nano-Bio Electron Microscopy Research Group; Korea Basic Science Institute (KBSI); Daejeon 305-338 Republic of Korea