Li-Assisted Low-Temperature Phase Transitions in Solution-Processed Indium Oxide Films for High-Performance Thin Film Transistor

Lithium (Li)-assisted indium oxide (In(2)O(3)) thin films with ordered structures were prepared on solution-processed zirconium oxide (ZrO(2)) gate dielectrics by spin-casting and thermally annealing hydrated indium nitrate solutions with different Li nitrate loadings. It was found that the Li-assisted In precursor films on ZrO(2) dielectrics could form crystalline structures even at processing temperatures (T) below 200 °C. Different In oxidation states were observed in the Li-doped films, and the development of such states was significantly affected by both temperature and the mol% of Li cations, [Li(+)]/([In(3+)] + [Li(+)]), in the precursor solutions. Upon annealing the Li-assisted precursor films below 200 °C, metastable indium hydroxide and/or indium oxyhydroxide phases were formed. These phases were subsequently transformed into crystalline In(2)O(3) nanostructures after thermal dehydration and oxidation. Finally, an In(2)O(3) film doped with 13.5 mol% Li(+) and annealed at 250 °C for 1 h exhibited the highest electron mobility of 60 cm(2) V(−1) s(−1) and an on/off current ratio above 10(8) when utilized in a thin film transistor.