Vertical Electrolyte-Gated Transistors Based on Printed Single-Walled Carbon Nanotubes

For all-printed circuits, the critical device dimensions, in particular, the channel length in lateral field-effect transistors (FETs), are limited by the printing resolution and alignment accuracy. In contrast, the channel length in vertical electrolyte-gated transistors (VEGTs) is mainly defined by the film thickness and can be easily scaled down to less than 100 nm to achieve high current densities. For practical VEGTs, the printed semiconductor must be highly porous to enable efficient electrolyte gating by ion penetration. Here, we use aerosol-jet (AJ)-printed layers of polymer-sorted (6,5) single-walled carbon nanotubes with film thicknesses from less than 50 nm to several hundred nanometers as the semiconducting layer sandwiched between evaporated (gold) or printed (silver nanoparticle) metal electrodes and gated by an ionic-liquid-based ion gel. Vertical charge transport in the obtained three-dimensional nanotube networks is confirmed via conductive AFM measurements. The nanotube network VEGTs exhibit transfer characteristics with good on/off ratios and high on-conductances. The effective gating of the semiconducting nanotubes throughout the entire active area of several hundred mu m(2) is corroborated by in situ Raman spectroscopy. The overall transistor performance scales with film thickness and electrode overlap and is comparable to photolithographically structured lateral electrolyte-gated transistors with 2 m short channels. VEGTs could thus be a viable replacement of printed lateral FETs that require too much space for the desired drive currents.