High performance semiconducting enriched carbon nanotube thin film transistors using metallic carbon nanotubes as electrodes

Abstract

High-performance solution-processed short-channel carbon nanotube (CNT) thin film transistors (TFTs) are fabricated using densely aligned arrays of metallic CNTs (m-CNTs) for the source and drain electrodes, while aligned arrays of semiconducting enriched CNTs (s-CNTs) are used as the channel material. The electrical transport measurements at room temperature show that using the m-CNT as the contact for the s-CNT array devices with a 2 μm channel length performed superior to those where the control Pd was the contact. The m-CNT contact devices exhibited a maximum (average) on-conductance of 36.5 μS (19.2 μS), a transconductance of 2.6 μS (1.2 μS), a mobility of 51 cm² V⁻¹ s⁻¹ (25 cm² V⁻¹ s⁻¹), and a current on–off ratio of 1.1 × 10⁶ (2.5 × 10⁵). These values are almost an order of magnitude higher than that of control Pd contact devices with the same channel length and s-CNT linear density. The low temperature charge transport measurements suggest that these improved performances are due to the m-CNT contact s-CNT devices having a lower Schottky barrier compared to the Pd contact s-CNT devices. We attribute this lower Schottky barrier to the unique geometry of our devices. In addition to using semiconducting enriched CNTs, our results suggest that using the metallic CNT as an electrode can significantly enhance the performance of CNT TFTs.