Laser patterned polymer/nanotube composite electrodes for nanowire transistors on flexible substrates

TL;DR

This paper demonstrates a low-cost method for fabricating flexible nanowire transistors using laser-patterned conductive polymer/nanotube composite electrodes, achieving high conductivity and good transistor performance.

Contribution

It introduces a laser patterning technique for PEDOT:PSS/f-MWCNT electrodes on flexible substrates for nanowire transistors, combining improved conductivity and device integration.

Findings

Conductivity of PEDOT:PSS increased four orders of magnitude with f-MWCNT.

Laser patterned electrodes enabled successful nanowire transistor fabrication.

Transistors exhibited p-type conduction with ON/OFF ratio of ~200.

Abstract

Fabrication techniques such as laser patterning offer excellent potential for low cost and large area device fabrication. Conductive polymers can be used to replace expensive metallic inks such as silver and gold nanoparticles for printing technology. Electrical conductivity of the polymers can be improved by blending with carbon nanotubes. In this work, formulations of acid functionalised multiwall carbon nanotubes (f-MWCNT) and poly (ethylenedioxythiophene) [PEDOT]: polystyrene sulphonate [PSS] were processed, and thin films were prepared on plastic substrates. Conductivity of PEDOT: PSS increased almost four orders of magnitude after adding f-MWCNT. Work function of PEDOT:PSS/f-MWCNT films was ~ 0.5eV higher as compared to the work function of pure PEDOT:PSS films, determined by Kelvin probe method. Field-effect transistors source-drain electrodes were prepared on PET plastic substrates where PEDOT:PSS/f-MWCNT were patterned using laser ablation at 44mJ/pulse energy to define 36 micron electrode separation. Silicon nanowires were deposited using dielectrophoresis alignment technique to bridge the PEDOT:PSS/f-MWCNT laser patterned electrodes. Finally, top-gated nanowire field effect transistors were completed by depositing parylene C as polymer gate dielectric and gold as the top-gate electrode. Transistor characteristics showed p-type conduction with excellent gate electrode coupling, with an ON/OFF ratio of ~ 200. Thereby, we demonstrate the feasibility of using high workfunction, printable PEDOT:PSS/MWCNT composite inks for patterning source/drain electrodes for nanowire transistors on flexible substrates.