Gyeong-Su Park*, Hyuksang Kwon, Dong Wook Kwak, Seong Yong Park, Minseok Kim, Jun-Ho Lee, Hyouksoo Han, Sung Heo, Xiang Shu Li, Jae Hak Lee, Young Hwan Kim, Jeong-Gun Lee, Woochul Yang, Hoon Young Cho, Seong Keun Kim* and Kinam Kim, Nano Lett., 12, 1638-1642 (2012)