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

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 precursorwith an [In]/[Zn] ratio of 3:1 exhibit an on-off current ratio of 10(6) with a calculated saturation mobility of 14.1 cm(2) V-1 s(-1) +/- 1.1 cm(2) V-1 s(-1) at a drain voltage of 40 V. The demonstrated route to non-toxicmolecular 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.