Flexible CMOS-Like Circuits Based on Printed P-Type and N-Type Carbon Nanotube Thin-Film Transistors

Abstract

P-type and n-type top-gate carbon nanotube thin-film transistors (TFTs) can be selectively and simultaneously fabricated on the same polyethylene terephthalate (PET) substrate by tuning the types of polymer-sorted semiconducting single-walled carbon nanotube (sc-SWCNT) inks, along with low temperature growth of HfO₂ thin films as shared dielectric layers. Both the p-type and n-type TFTs show good electrical properties with on/off ratio of ≈10⁵ , mobility of ≈15 cm² V^-1 s^-1 , and small hysteresis. Complementary metal oxide semiconductor (CMOS)-like logic gates and circuits based on as-prepared p-type and n-type TFTs have been achieved. Flexible CMOS-like inverters exhibit large noise margin of 84% at low voltage (1/2 V_dd = 1.5 V) and maximum voltage gain of 30 at V_dd of 1.5 V and low power consumption of 0.1 μW. Both of the noise margin and voltage gain are one of the best values reported for flexible CMOS-like inverters at V_dd less than 2 V. The printed CMOS-like inverters work well at 10 kHz with 2% voltage loss and delay time of ≈15 μs. A 3-stage ring oscillator has also been demonstrated on PET substrates and the oscillation frequency of 3.3 kHz at V_dd of 1 V is achieved.

Keywords: N-type; flexible; polymer-sorted; printed circuits; thin-film transistors.