Tuning the charge carrier polarity of roll-to-roll gravure printed carbon nanotube-based thin film transistors by an atomic layer deposited alumina nanolayer

Abstract

Charge carrier polarity tuning in printed thin film transistors (TFTs) is a crucial step in order to obtain complementary printed devices. In this work, we studied the effect of an Al₂O₃ passivation layer on printed single-walled carbon nanotube (SWCNT) based TFTs to tune the charge carrier polarity. By varying the atomic layer deposition (ALD) temperature and Al₂O₃ layer thickness, we can tune the doping degree of Al₂O₃ to tailor the polarity of printed SWCNT-based TFTs (SWCNT-TFTs). The precise control of threshold voltage (V_th) and polarity from p-type to well-balanced ambipolar, and n-type SWCNT-TFTs is successfully demonstrated with high repeatability by optimizing the ALD temperature and Al₂O₃ layer thickness based on 20 printed samples per test. As a proof-of-concept, inverter logic circuits using the SWCNT-TFT with different polarity types are demonstrated. The ambipolar device-based inverter exhibits a voltage gain of 3.9 and the CMOS-based inverter exhibits a gain of approximately 4.3, which is comparable to the current roll-to-roll (R2R) printed inverter circuits. Different thicknesses of Al₂O₃ layer, coated by the ALD at different temperatures and thicknesses, provide a deep understanding of the device fabrication and control process to implement the tailored doping method to efficiently realize R2R printed SWCNT-TFT-based complementary electronic devices.