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 (mCNTs) as source and drain electrodes, and aligned arrays of semiconducting enriched CNTs (s-CNTs) as channel material. The electrical transport measurements at room temperature show that the m-CNT contacted s-CNT array devices with a 2 µm channel length perform superiorly to those of control Pd contacted s-CNT devices. The m-CNT contacted devices exhibit a maximum (average) on-conductance of 36.5 µS (19.2 µS), transconductance of 2.6 µS (1.2 µS), mobility of 51 cm 2 /Vs (25 cm 2 /Vs), and current onoff ratio of 1.1×10 6 (2.5×10 5 ). These values are almost an order of magnitude higher than that of control Pd contacted 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 lower charge injection barrier of m-CNT/s-CNT array devices compared to Pd/s-CNT array devices. We attribute the lower injection barrier to unique geometry of our devices. In addition to using semiconducting enriched CNT, our results suggest that using metallic CNT as an electrode can significantly enhance the performance of CNT TFTs.

All‐Carbon Thin‐Film Transistors as a Step Towards Flexible and Transparent Electronics

“…It has been found that the oncurrent, transconductance, mobility and on/off current ratio of devices with metallic CNT electrodes are up to one order of magnitude higher than those of devices fabricated using metal electrodes, due to the lower Schottky barrier of the semiconducting CNT channel with CNT electrodes. [194] In 2006, Cao et al reported a bendable and transparent all-CNT TFT, as shown in Figure 8. [195] CVD-synthesized CNT thin films with low and high coverages respectively serve as active channel and source/drain/gate electrodes, and a bilayer of Al 2 O 3 and epoxy/elastomer as dielectric.…”

Assembly and Electronic Applications of Colloidal Nanomaterials

“…The dashed lines and solids lines represent fits using two different models. [405] Copyright 2014, The Royal Society of Chemistry. [399] Copyright 2010, American Chemical Society.…”

“…In comparison to metallic nanoparticles, SWCNTs are lighter, stronger, and more chemically and thermally stable. [35] The conductivity of SWCNT networks can be further improved by using high-purity metallic SWCNTs, [405] aligned SWCNTs, [418] or chemical doping. Random SWCNT conductive networks prepared by spray coating have electrical conductivities of 1.1 × 10 3 S cm −1 .…”

“…[26] The resulting SWCNT electrodes can be coupled with SWCNT semiconducting networks for flexible or stretchable FETs. [405] With such electrodes, SWCNT FETs show an order of magnitude higher performance in terms of on-state conductance and mobility than FETs with the same geometry but using conventional Pd contacts. [134] The conductivity of iodine-doped, aligned SWCNT yarns can be as high as 5 × 10 4 S cm −1 at room temperature, [418] but the harsh production process and volatility of the dopants may make them unsuitable for FET electrodes.…”

Random networks of carbon nanotubes optimized for transistor mass-production: searching for ultimate performance

“…The contact conductances for the internal nodes are assigned the following values: (i) 0.1e 2 /h for the junction between two m-CNTs or between two s-CNTs and (ii) 100 times lower conductance for the junction between one m-CNT and one s-CNT, as we neglect the rectifying behavior under low-bias conditions [31,41]. The contact resistance at the boundary nodes is neglected since electrodes fabricated using, for example, Au [1], Pd [38], or aligned arrays of m-CNTs [42] yield good Ohmic contact to CNTs. Therefore, if a CNT intersects an electrode the potential of the electrode is applied to the intersection point.…”