SiCCarbon Nanotube and TiCCarbon Nanotube Junctions

Zhang et al. [8] found an easy and simple approach to fabricate single-walled carbon nanotube-carbide junctions based on solid-solid reaction at a high temperature from 800 °C to 1000 °C. This method as shown in Figure 13 is based on a direct solid-solid reaction: C (carbon nano-tube)+ M (solid) = MC (solid), where M could be either silicon or a transition metal. The carbide initially forms at the C/M interface once a sufficient temperature is reached for the reaction to occur [152]. They found that the self-diffusion rate through bulk SiC or transition-metal carbide is extremely slow in the temperature range of 800 °C to 1000 °C, which guarantees a clean nanoscale interface between SiC and carbon nanotube.

In the experiments, the Si, Ti, and Nb substrates were thinned with perforations by means of conventional transmission electron microscopy sample preparation techniques.

After reaction

Figure 13. A schematic description of the method for fabricating nano-tube/carbide heterostructures by a solid-solid reaction. Reprinted with permission from [8], Y. Zhang et al., Science 285, 1719 (1999). © 1999, American Association for the Advancement of Science.

After reaction

Figure 13. A schematic description of the method for fabricating nano-tube/carbide heterostructures by a solid-solid reaction. Reprinted with permission from [8], Y. Zhang et al., Science 285, 1719 (1999). © 1999, American Association for the Advancement of Science.

Then single-walled carbon nanotubes were deposited on the substrates. The prepared substrates were heated in the ultrahigh-vacuum TEM column or in a side chamber either by an infrared heating lamp or by electrical current heating the substrate. They found that ¿S-phase SiC was formed at the junction between silicon and single-walled carbon nano-tube bundles according to high-resolution TEM as shown Figure 14. NaCl-structured TiC was obtained between Ti substrate and carbon nanotubes (Fig. 15). Improvement of the contact conductance between carbon nanotubes and Ti electrodes was demonstrated through the formation of TiC junctions (Fig. 15). This method has been used by other researchers to make ohmic contact between Ti electrode and semiconducting nanotubes by annealing devices above 700 °C in fabrication of nanotube transistors [153].

It was also found that carbon nanotube can react with Ti scanning tunneling microscope tip with solid-solid reaction after the nanotube was attached to the tip by using a nanomanipulator [8]. This kind of probe is supposed to be more robust than nanotube attached by glue or chemical vapor deposition growth [154, 155].

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