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Scanned Probe Microscopy Of Electronic Transport In Carbon Nanotubes
PHYSICAL REVIEW LETTERS, no. 26 (2000): 6082-6085
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摘要
We use electrostatic force microscopy and scanned gate microscopy to probe the conducting properties of carbon nanotubes at room temperature. Multiwalled carbon nanotubes are shown to be diffusive conductors, while metallic single-walled carbon nanotubes are ballistic conductors over micron lengths. Semiconducting single-walled carbon nan...更多
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简介
- Electronic devices constructed from single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs) show remarkable behavior.
- Doped semiconducting SWNTs, on the other hand, have much higher resistances, and recent experiments suggest that transport is not diffusive but instead limited by a series of large barriers along the nanotube length [9].
- The authors use electrostatic force microscopy (EFM) [14] and scanned gate microscopy (SGM) [15] to directly probe the nature of conduction in SWNTs and MWNTs. By using an atomic force microscope (AFM) tip as a local voltmeter (EFM), the authors separately measure the intrinsic resistance and contact resistances of SWNTs and MWNTs. The authors show for the first time that in metallic SWNTs the measured resistance is due to contact resistance, i.e., electron transport is ballistic.
重点内容
- Electronic devices constructed from single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs) show remarkable behavior
- We note that scanned gate measurements showed no appreciable signal on multiwalled carbon nanotubes,1%͒, indicating that the tip did not significantly perturb the conducting properties of the sample
- Image [Fig. 4(a)] shows that the voltage drops occur along the nanotube length, at the junctions between segments
- Electrostatic force microscopy and scanned gate microscopy show that conduction in semiconducting SWNTs is dominated by a series of barriers along their length
结果
- By using the AFM tip as a local gate (SGM), the authors directly image individual scattering sites in semiconducting SWNTs and show that a series of large barriers limit transport.
- Scanned gate microscopy images this perturbation by measuring the conductance of the sample as a function of tip position.
- Because of the less local nature of the ac-EFM measurement, there is a background signal due to stray capacitive coupling of the tip to the large metal electrodes.
- The linear voltage drop indicates that the tube behaves as a diffusive conductor with a well-defined resistance per unit length, RiL ϳ 10 kVmm. This confirms the results from previous transport [11] and scanned contact [21] measurements of MWNTs. The authors measured the left and right contact resistances to be 6 6 2 kV and 3 6 2 kV, respectively.
- The authors note that scanned gate measurements showed no appreciable signal on MWNTs,1%͒, indicating that the tip did not significantly perturb the conducting properties of the sample.
- The authors turn to metallic SWNTs. The authors first discuss the measurements of the device shown in Fig. 1 before electrical failure.
- SGM showed no measurable effects, indicating that the tip did not perturb the conducting properties.
- This is consistent with low temperature measurements where similar contacts to SWNTs have been shown to lead to Coulomb blockade [1,2] and have been exploited to observe Luttinger liquid tunneling behavior in nanotube devices [24].
结论
- Image [Fig. 4(a)] shows that the voltage drops occur along the nanotube length, at the junctions between segments.
- Unlike for the MWNTs and metallic SWNTs, scanned gate microscopy showed very strong effects for this semiconducting SWNT bundle, as shown in Fig. 4(b).
- EFM and SGM show that conduction in semiconducting SWNTs is dominated by a series of barriers along their length.
基金
- This work was supported by DOE (Basic Energy Sciences, Materials Sciences Division, the sp2 Materials Initiative) and by DARPA (Moletronics Initiative)
- A. was partially supported by DARPA (Advanced Lithography Program under DOE Contract No DE-AC03-76SF0009)
引用论文
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