The Effects of Hydrogen Annealing on Carbon Nanotube Field-Effect Transistors

Takashi Uchino; Greg N Ayre; David C Smith; John L Hutchison; C H de Groot; Peter Ashburn

doi:10.3390/nano11102481

The Effects of Hydrogen Annealing on Carbon Nanotube Field-Effect Transistors

Nanomaterials (Basel). 2021 Sep 23;11(10):2481. doi: 10.3390/nano11102481.

Authors

Takashi Uchino¹, Greg N Ayre², David C Smith², John L Hutchison³, C H de Groot⁴, Peter Ashburn⁴

Affiliations

¹ Department of Electrical and Electronic Engineering, Tohoku Institute of Technology, Sendai 982-8577, Japan.
² School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK.
³ Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK.
⁴ School of Electronics and Computer Science, University of Southampton, Southampton SO17 1BJ, UK.

Abstract

We have systematically investigated the effects of hydrogen annealing on Ni- and Al-contacted carbon nanotube field-effect transistors (CNTFETs), whose work functions have not been affected by hydrogen annealing. Measured results show that the electronic properties of single-walled carbon nanotubes are modified by hydrogen adsorption. The Ni-contacted CNTFETs, which initially showed metallic behavior, changed their p-FET behavior with a high on-current over 10 µA after hydrogen annealing. The on-current of the as-made p-FETs is much improved after hydrogen annealing. The Al-contacted CNTFETs, which initially showed metallic behavior, showed unipolar p-FET behavior after hydrogen annealing. We analyzed the energy band diagrams of the CNTFETs to explain experimental results, finding that the electron affinity and the bandgap of single-walled carbon nanotubes changed after hydrogen annealing. These results are consistent with previously reported ab initio calculations.

Keywords: bandgap; carbon nanotube; electron affinity; field-effect transistors; hydrogen annealing.