Vacuum-Free Liquid-Metal-Printed 2D Indium-Tin Oxide Thin-Film Transistor for Oxide Inverters.

A cost-effective, vacuum-free, liquid-metal-printed two-dimensional (2D) (∼1.9 nm-thick) tin-doped indium oxide (ITO) thin-film transistor (TFT) was developed at the maximum process temperature of 200 °C. A large-sized 2D-ITO channel layer with an electron density of ∼1.2 × 10 19 cm -3 was prepared in an ambient atmosphere. The 2D-ITO-TFT operated in full depletion with a threshold voltage of -2.1 V and demonstrated good TFT device characteristics such as a high saturation mobility of ∼27 cm 2 V -1 s -1 , a small subthreshold slope of <382 mV decade -1 , and a large on/off-current ratio of >10 9 . The TFT device simulation analysis found that the 2D-ITO-TFT performances were controlled by the shallow acceptor-like in-gap defects spreading in the midgap region of over 1.0 eV below the conduction band minimum. Post-thermal annealing tuned the electron density of the 2D-ITO channel and enabled it to produce enhancement and depletion-mode 2D-ITO-TFTs. A full signal swing zero- V GS -load n-type metal-oxide semiconductor (NMOS) inverter composed of depletion-load/enhancement-driver 2D-ITO-TFTs and a complementary inverter with p-channel 2D-SnO-TFT were successfully demonstrated using all 2D-oxide-TFTs.