In situ manipulation and electrical characterization of multiwalled carbon nanotubes by using nanomanipulators under scanning electron microscopy

The results of in situ manipulation and electrical transport characterization of individual multiwalled carbon nanotubes (MWCNTs) grown on a nickel tip by using a piezoelectric nanomanipulation system operating in a scanning electron microscope chamber have been reported. The growth of MWCNT directly on nickel wire by chemical vapor deposition technique ensures good electrical contact with the catalyst substrate. Using the electron beam induced welding, a full characterization of electronic properties of several MWCNTs has been explored without the usual postprocessing methods which may alter, in principle, the intrinsic properties of the carbon nanotube (CNT). Thanks to the high mechanical and electrical stability ensured by the electron beam welding procedure, a detailed study of the modification of CNT electrical transport properties under CNT buckling has been performed. The crucial role played by the structural defects in determining an irreversibility of a long MWCNT $I\text{−}V$ characteristic under mechanical stress has been clearly evidenced. Finally, by a proper sequence of CNT/tip welding and movement, the potential in creating an Ohmic junction between two nanotubes has been demonstrated, opening the route to a systematic investigation of one of the most fundamental aspect of CNT physics.

Figure 1

Typical (a) SEM, (b) TEM, and (c) high resolution TEM images of the CNTs as-grown on nickel substrate.

Figure 2

SEM image of an individual MWCNT protruding from the nickel surface. (b) Spontaneous adhesion of the MWCNT on the tungsten probing tip due to the electrostatic interaction.

Figure 3

SEM image of the MWCNT/tungsten tip junction. Inset shows the CNT/tip superimposition region exposed to the $10\mathrm{keV}$ electron beam during the contact formation.

Figure 4

Evolution of (a) $I\text{−}V$ curve and (b) overall low field resistance as a function of the exposure time to the electron beam onto a selected CNT/tip superimposition area. The initial value of resistance $(\sim {10}^9\Omega )$ has not been reported for scaling reasons.

Figure 5

SEM images of (a) MWCNT connected to the tungsten tip and (b) after electron beam bombardment of the MWCNT middle region has been performed. Note (as indicated by the arrow) the carbonaceous deposit formation corresponding to the electron beam exposed areas (CNT/tip junction and middle region of the CNT).

Figure 6

$I\text{−}V$ characteristics of various MWCNTs obtained after prolonged and selective exposure of the CNT/tip contact area to $10\mathrm{keV}$ electron beam. The structural parameter and the corresponding overall resistance value of the various nanotubes, to which the numbers 1–6 are referred, are reported in Table .

Figure 7

SEM images of the various CNT/tip positions (A, B, and C) during the nanotube buckling process.

Figure 8

(a) $I\text{−}V$ curve and (b) overall resistance values corresponding to the different CNT positions reported in Fig. 7.

Figure 9

SEM images showing the steps for the CNT/CNT junction formation: (a) CNT/tip welding and mechanical removal of the MWCNT. (b) Selection of the CNT/CNT contact area. (c) Selective irradiation of the CNT/CNT contact area with final formation of carbonaceous deposit (indicated by the white arrow) (d) $I\text{−}V$ characteristic of the junction between two MWCNTs.