Detection of invisible phonon modes in individual defect-free carbon nanotubes by gradient-field Raman scattering
Yang Feng1, 3, 4, Ji Yinglu2, ‡, Zhang Xiao1, 4, Fan Qingxia1, 4, Zhang Nan1, 4, Gu Xiaogang1, 3, 4, Xiao Zhuojian1, 3, 4, Zhang Qiang1, 4, Wang Yanchun1, 3, Wu Xiaochun2, 4, Li Junjie1, Zhou Weiya1, 3, 4, †
       

(color online) (a) TEM image of 30 nm Au NPs. The scale bar is 50 nm. (b) SEM image of a SWNT covered by Au NP cluster, in which the white arrows denote the position of the SWNT. The scale bar is 200 nm. (c) Dark field spectrum of the cluster shown in panel (b).