High-mobility metal-oxide thin-film transistors by spray deposition of environmentally friendly precursors

• Non-toxic precursors for solution processing of metal oxides
• Robust and facile precursor chemistry with low-level handling requirements
• Precursor miscibility for customized mixed metal-oxide materials
• Low-temperature processing (at 250 °C) of precursor solutions by spray pyrolysis
• High-performance InZnO thin-film transistors (Ion/off = 106, μsat = 14.1 cm2 V− 1 s− 1)

The synthesis of versatile, and non-toxic precursors for ambient-air deposition of semiconducting metal-oxide thin films by spray pyrolysis is reported. The resulting thin films yield stable and reproducible performance in thin-film transistors. The precursors are based on reactions of metal salts and an organic ammonium source in water. The precursor preparation is highly versatile with respect to low-level handling requirements (i.e. in air) and miscibility for the synthesis of customized mixed metal oxides. The precursor solutions are deposited by spray pyrolysis and integrated into bottom-gate test structures with staggered source and drain contacts. Indium zinc oxide thin films deposited from a precursor with an [In]/[Zn] ratio of 3:1 exhibit an on-off current ratio of 106 with a calculated saturation mobility of 14.1 cm2 V− 1 s− 1 ± 1.1 cm2 V− 1 s− 1 at a drain voltage of 40 V. The demonstrated route to non-toxic molecular precursors for low-temperature thin-film processing in ambient atmosphere benefits from low cost of educts, environmentally friendly solvents, minimized health risk when compared to nanoparticle processing, and an excellent performance for electronic applications.