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Ballistic carbon nanotube field-effect transistors

Abstract

A common feature of the single-walled carbon-nanotube field-effect transistors fabricated to date has been the presence of a Schottky barrier at the nanotube–metal junctions1,2,3. These energy barriers severely limit transistor conductance in the ‘ON’ state, and reduce the current delivery capability—a key determinant of device performance. Here we show that contacting semiconducting single-walled nanotubes by palladium, a noble metal with high work function and good wetting interactions with nanotubes, greatly reduces or eliminates the barriers for transport through the valence band of nanotubes. In situ modification of the electrode work function by hydrogen is carried out to shed light on the nature of the contacts. With Pd contacts, the ‘ON’ states of semiconducting nanotubes can behave like ohmically contacted ballistic metallic tubes, exhibiting room-temperature conductance near the ballistic transport limit of 4e2/h (refs 4–6), high current-carrying capability (25 µA per tube), and Fabry–Perot interferences5 at low temperatures. Under high voltage operation, the current saturation appears to be set by backscattering of the charge carriers by optical phonons. High-performance ballistic nanotube field-effect transistors with zero or slightly negative Schottky barriers are thus realized.

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Figure 1: Pd-contacted long (L = 3 µm) and short (L = 300 nm) back-gated SWNT devices formed on the same nanotubes on SiO2/Si.
Figure 2: Properties of the metal/semiconducting-SWNT contacts as influenced by in situ metal work-function modification.
Figure 3: Geometry/transport-property relations for Pd-contacted semiconducting nanotubes.
Figure 4: Room-temperature electrical properties of high-performance SWNT-FETs (tox = 67 nm).

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Acknowledgements

We thank P. McEuen, W. Harrison, D. Antoniadis, J. Bokor and J. Tersoff for insights and sharing preprints/unpublished results, and D. Wang for SEM. The work at Stanford was supported by the MARCO MSD Focus Center, DARPA/Moletronics, SRC/AMD, and the Packard, Alfred Sloan and Dreyfus foundations. The work at Purdue was supported by the National Science Foundation Nanoscale Modeling and Simulation Program and by the Network for Computational Nanotechnology.

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Correspondence to Hongjie Dai.

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Javey, A., Guo, J., Wang, Q. et al. Ballistic carbon nanotube field-effect transistors. Nature 424, 654–657 (2003). https://doi.org/10.1038/nature01797

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