Facile fabrication of carbon nanotube network thin film transistors for device platforms

Abstract

Carbon nanotube network thin film transistors with channel lengths of 10-40 μm are fabricated from a nanotube buckypaper with 99% semiconducting carbon nanotubes by surfactant free solution routes. The carbon nanotubes are suspended in 1,2-dichlorobenzene by ultrasonication at concentrations of 7.9 μg/ml, 3.4 μg/ml and 2.6 μg/ml, resulting in carbon nanotube field effect transistors with tube densities ranging from 5 tube/μm2 up to 32 tube/μm2. The device percolation threshold is 11 tube/μm2 with optimum device performances of on/off current ratio 7200, mobility 0.55 cm2/V·s and Vth = +1 V. Devices with tube density above the percolation threshold are typically metallic-like. By encapsulating with poly-4-vinylphenol cross-linked with poly-(melamine-co-formaldehyde), the hysteresis becomes independent of channel length and the device performance approaches the best devices at the percolation threshold.