Heterojunction Transistors Printed via Instantaneous Oxidation of Liquid Metals

Semiconducting transparent metal oxides are critical high mobility materials for flexible optoelectronic devices such as displays. We introduce the continuous liquid metal printing (CLMP) technique to enable rapid roll-to-roll compatible deposition of semiconducting two-dimensional (2D) metal oxide heterostructures. We leverage CLMP to deposit 10 cm²-scale nanosheets of InO and GaO in seconds at a low process temperature (T < 200 °C) in air, fabricating heterojunction thin film transistors with 100× greater I_on/I_off, 4× steeper subthreshold slope, and a 50% increase in mobility over pure InO channels. Detailed nanoscale characterization of the heterointerface by X-ray photoelectron spectroscopy, UV-vis, and Kelvin probe elucidates the origins of enhanced electronic transport in these 2D heterojunctions. This combination of CLMP with the electrostatic control induced by the heterostructure architecture leads to high performance (μ_lin up to 22.6 cm²/(V s)) while reducing the process time for metal oxide transistors by greater than 100× compared with sol-gels and vacuum deposition methods.