Effect of Polymer Gate Dielectrics on Charge Transport in Carbon Nanotube Network Transistors: Low-k Insulator for Favorable Active Interface

Seung-Hoon Lee; Yong Xu; Dongyoon Khim; Won-Tae Park; Dong-Yu Kim; Yong-Young Noh

doi:10.1021/acsami.6b06882

Effect of Polymer Gate Dielectrics on Charge Transport in Carbon Nanotube Network Transistors: Low-k Insulator for Favorable Active Interface

ACS Appl Mater Interfaces. 2016 Nov 30;8(47):32421-32431. doi: 10.1021/acsami.6b06882. Epub 2016 Nov 16.

Authors

Seung-Hoon Lee^{1

2}, Yong Xu², Dongyoon Khim³, Won-Tae Park², Dong-Yu Kim¹, Yong-Young Noh²

Affiliations

¹ Department of Nanobio Materials and Electronics, School of Materials Science and Engineering, Heeger Center for Advanced Materials, Gwangju Institute of Science and Technology (GIST) , 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, Republic of Korea.
² Department of Energy and Materials Engineering, Dongguk University , 26 Pil-dong, 3-ga, Jung-gu, Seoul 100-715, Republic of Korea.
³ Department of Physics and Centre for Plastic Electronics, Blackett Laboratory, Imperial College London , London SW7 2AZ, U.K.

PMID: 27933829
DOI: 10.1021/acsami.6b06882

Abstract

Charge transport in carbon nanotube network transistors strongly depends on the properties of the gate dielectric that is in direct contact with the semiconducting carbon nanotubes. In this work, we investigate the dielectric effects on charge transport in polymer-sorted semiconducting single-walled carbon nanotube field-effect transistors (s-SWNT-FETs) by using three different polymer insulators: A low-permittivity (ε_r) fluoropolymer (CYTOP, ε_r = 1.8), poly(methyl methacrylate) (PMMA, ε_r = 3.3), and a high-ε_r ferroelectric relaxor [P(VDF-TrFE-CTFE), ε_r = 14.2]. The s-SWNT-FETs with polymer dielectrics show typical ambipolar charge transport with high ON/OFF ratios (up to ∼10⁵) and mobilities (hole mobility up to 6.77 cm² V^-1 s^-1 for CYTOP). The s-SWNT-FET with the lowest-k dielectric, CYTOP, exhibits the highest mobility owing to formation of a favorable interface for charge transport, which is confirmed by the lowest activation energies, evaluated by the fluctuation-induced tunneling model (FIT) and the traditional Arrhenius model (E_aFIT = 60.2 meV and E_aArr = 10 meV). The operational stability of the devices showed a good agreement with the activation energies trend (drain current decay ∼14%, threshold voltage shift ∼0.26 V in p-type regime of CYTOP devices). The poor performance in high-ε_r devices is accounted for by a large energetic disorder caused by the randomly oriented dipoles in high-k dielectrics. In conclusion, the low-k dielectric forms a favorable interface with s-SWNTs for efficient charge transport in s-SWNT-FETs.

Keywords: carbon nanotube field-effect transistors; charge transport; conjugated polymer wrapped single wall carbon nanotube; gate dielectrics; polymer dielectrics.