Ultrathin\nα‑Bi<sub>2</sub>O<sub>3</sub> Thin-Film Transistor for\nCost-Effective Oxide-TFT Inverters

Electronics is advancing toward greater\ndiversity and sustainability\nby prioritizing energy efficiency and cost-effectiveness. Metal oxide\nthin-film transistor (TFT) represents a technology at the forefront\nof advancing next-generation sustainable electronics, and exploring\noxide channel compositions is a crucial step in opening opportunities\nfor developing next-generation device applications. This study presents\nthe first development of n-channel α-Bi<sub>2</sub>O<sub>3</sub>-TFTs using a 4 nm ultrathin channel prepared by a cost-effective\nvacuum-free and solvent-free liquid metal printing method in ambient\nair. Even the pristine device exhibited a clear TFT action but required\na large negative gate bias to turn off due mainly to excess carriers\nfrom oxygen vacancy in the α-Bi<sub>2</sub>O<sub>3</sub> channel.\nOxygen-containing post-annealing reduced both channel carrier and\nsubgap defect densities, enabling the development of depletion and\nenhancement-type α-Bi<sub>2</sub>O<sub>3</sub>-TFTs with the\nsaturation mobility of 2–4 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>. Two types of oxide-TFT-based inverter circuits,\nzero-V<sub>GS</sub>-NMOS and CMOS inverters, were fabricated by using\nα-Bi<sub>2</sub>O<sub>3</sub>-TFTs, operating in a high voltage\ngain of over 130. This work demonstrates the potential of oxide semiconductor\nmaterials toward the development of next-generation sustainable electronics.