Air-stable N-type printed carbon nanotube thin film transistors for CMOS logic circuits

Abstract

The lack of long-term air-stable and solution-processed n-doping methods for printed single-walled carbon nanotube (SWCNT) thin film transistors (TFTs) limits their integrations into printed complementary metal-oxide-semiconductor (CMOS) circuits. In this paper, a new chemically modified epoxy amine ink was developed as the chemical dopant and encapsulant to enable the uniform n-type SWCNT-TFTs with long-term air stability (6 months). The epoxy amine inks were dropped onto the printed p-type TFT device channels in a single-step solution process. As a result, printed top-contact n-type SWCNT-TFTs were obtained with well-balanced electrical chararcteristics comparable to their p-type counterparts. The matched p-type and n-type SWCNT-TFTs were thus integrated into the printed CMOS inverters and NAND gates, which have both achieved proper logic operation at supply voltages below 1 V. In particular, the CMOS inverters could operate with VDD down to 0.3V with associated peak power consumption of 0.06 μW, showing full rail-to-rail output swings with voltage gains up to 22, trip voltages of ∼VDD/2, and maximum noise margin of 0.42 V at VDD = 1.1 V (∼76.4% of VDD/2). Furthermore, the static characteristics of CMOS inverters could be maintained for 3 months with negligible changes, proving the feasibility of this long-term air-stable n-doping method.