Figure 4: TEM and STEM images of CNT–graphene junctions.

(a,b) TEM images of the samples prepared by a solvent induce bundling method (Supplementary Fig. S12). The connection regions (roots) are directly observable. The cyan colour represents graphene planes and the blue colour represents the CNTs. (c,d) BF STEM images (band pass-filtered) of the CNT root regions. The blue colour represents CNTs and the cyan colour represents the additional shells on the root. Shown is a triple-walled nanotube in c and a double-walled nanotube in d. Scale bar in a–d, 5 nm. (e–h) High-resolution BF STEM images of the root of CNTs; e and g are original STEM images (band pass-filtered); f and h are colour-enhanced images. The cyan colour represents the open-end region. The blue colour, green colour and yellow colour represent the nanotube walls. (i) The proposed model of the graphene and CNT junction. The CNT is covalently bonded to the graphene plane with additional shells (shown in blue) at the root. Scale bar in e–h, 1 nm. (j) ADF STEM image of the CNT–graphene junction. The image was filtered with band pass filter as indicated in the inset in the upper right corner. Scale bar in j, 1 nm. (k,l) Theoretical models suggested the atomic structure of the CNT–graphene junction^12,13,14. Perspective view (k) and top-projected view (l). (m–t) High-resolution BF STEM images of CNT–graphene junctions. Scale bar in m and q, 0.5 nm. Scale bar in n–p, 0.2 nm. Scale bar in r–t, 0.1 nm. (m,q) The raw BF STEM images. (n,r) The high-resolution images after applying a filter (upper right inset) to the FFT of raw BF STEM images in the selected area (indicated as squares in m and q)³¹; n is from the red rectangle area in m; r is from the green rectangle area in q. (o,s) BF STEM images of junction areas with an overlayed structural sketch. (p,t) BF STEM images of junction areas with indicated areas for intensity profiles measurements. (u,v) Intensity profiles of indicated areas in p and t, respectively. (w) Simulated STEM image of CNT and graphene junction areas. Scale bar in w, 0.2 nm. (x) Simulated STEM image of CNT and graphene junction areas with an overlayed structural sketch. Scale bar in x, 0.2 nm.