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12/19/08

Chirality-Dependent Transport Properties of Double-Walled Nanotubes Measured in Situ on Their Field-Effect Transistors


Kaihui Liu, Wenlong Wang, Zhi Xu, Xuedong Bai, Enge Wang, Yagang Yao, Jin Zhang, Zhongfan Liu

J. AM. CHEM. SOC. 2009, 131, 62–63

 

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Double-walled carbon nanotubes (DWNTs), consisting of two coaxial tubes, possess mechanical properties and structural and thermal stability that are superior to single-walled carbon nanotubes. Interestingly, they provide an ideal structure for the fabrication of nanoscale functional composites, that is, chemical moieties are selectively introduced on the outer tubes as effective anchoring sites, while the inner tubes preserve their electronic properties. It is well known that the electronic property of a carbon nanotube, which shows potential in nanodevices, depends sensitively on the atomic structuresuniquely indexed with the chiral indices (n, m). It is therefore of essential significance to be able to probe the chirality resolved DWNTs so as to establish a direct correlation between the electrical transport properties and their chiral indices. Herein, we make progress on attaining this goal by building DWNT-based field-effect transistors (FETs) into a transmission electron microscope (TEM) through a new design, which allows for an accurate (n, m) assignment by electron diffraction (ED) on the same individual DWNTs that are electrically measured in situ inside the TEM. In this context, the transport properties of the chirality resolved DWNTs are systematically investigated for all the four types of DWNTs, and the probe of inner tubes can also be achieved in situ.

 

Figure 1. (a) A typical scanning electron micrograph of an isolated
ultralong DWNT grown onto the SiO2/Si slit substrate. (b) High-resolution
TEM image of the DWNT, acquired in the region as marked by the frame
at the slit edge in panel a. (c) The corresponding ED pattern of the same
DWNT (left, experimental; right, simulated). The (n, m) indices are identified
as (48,6)/(34,13). Scale bars: (a) 10 μm, (b) 5 nm.

 

Figure 2. Representative transfer characteristics (current vs gate-voltage)
of the four types of DWNTs. (a) M/M DWNT with indices of (48,6)/(34,13);
(b) M/S DWNT with indices of (22,19)/(19,12); (c) S/S DWNT with indices
of (38,6)/(23,13); (d) S/M DWNT with indices of (30,23)/(33,6). The inset
is the drawn atomic structure on the basis of the real (n, m) indices. The
drain voltage (Vds) are 4, 4, 100, and 4 mV in panels a, b, c, and d,
respectively.

 

 

Figure 3. Transfer characteristics of a M/S type DWNT (45,15)/(28,24)
before and after breaking down the outer tube. At the beginning, the current
has no response to gate voltage (top curve). After applying a high current
to break down the outer tube of DWNT, the transport exhibits a
semiconducting behavior of the inner tube (bottom curve).


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