Carbon nanotube/metal interface studied by cross-sectional transmission electron microscopy

We present the first results on the interface between carbon nanotube (CNT) and metal by cross-sectional high-resolution transmission electron microscopy and spatially resolved electron energy loss spectroscopy on Fe-filled CNTs. The iron core is mainly single crystalline $\alpha \text{−}\mathrm{Fe}$. Under specific orientation relationships, a semicoherent CNT/Fe interface forms, where local lattice mismatch is accommodated by “interface dislocations.” A $0.2–0.4\mathrm{eV}$ energy shift of the $\pi *$ peak of the carbon $K$-edge towards higher values is found at the interface. The results prove experimentally an interfacial bonding between the CNT wall and Fe.

Figure 1

Schematic of the geometry of (a) conventional plan-view TEM and (b) cross-sectional TEM. (c) BF image of a cross-sectional specimen.

Figure 2

(a) A bundle of Fe-filled MWCNTs, (b) HRTEM image of part of a CNT. The arrow indicates the ends of the innermost graphene layers.

Figure 3

(a) HRTEM of a cross section of a MWCNT with an empty core, showing defects in the walls arranged along the radius. (b) HRTEM of the central part of a cross section of a MWCNT filled with Fe.

Figure 4

(a) HRTEM of a cross section of a Fe filled CNT. (b) Lattice image of the central part of the Fe filling. (c) and (d) Interface region C and D marked in (a), respectively. The extra one half of the atomic planes of Fe, analogue to “interface dislocations,” are marked with $\perp$.

Figure 5

Line-scan EELS spectroscopy on a cross section of a Fe-filled CNT. (a) BF and HAADF images. The position of the line-scan is shown in the BF image as a white line, and the scattering geometry is sketched in the HAADF image. (b) ELNES of carbon $K$-edge. The sequential numbers of the spectra are indicated. (c) A close look of the carbon $\pi *$ peaks. Note that the peak position of the $\pi *$ peak obtained from the interface region shows a shift of $0.3\mathrm{eV}$ towards higher energy in comparison with the spectra obtained from the C-wall region.