Formation mechanism of solution-processed nanocrystalline InGaZnO thin film as active channel layer in thin-film transistor

Solution-processed indium gallium zinc oxide (IGZO) thin films as an active channel layer in thin-film transistors (TFTs) were successfully prepared by a spin-coating method using acetate- and nitrate-based precursors. In the range of 60-130°C, indium, gallium, and zinc precursors were dissociated and then hydrolyzed to metal hydroxides. InGa Zn2 O5 compound was synthesized at ∼196°C and crystallized at 305-420°C. A spin-coated IGZO film annealed at 450°C had smooth morphology and fine grains with an average size of ∼15 nm. In solution-processed IGZO TFTs using nanocrystalline films prepared at 450°C, the on-to-off ratio, a field effect mobility, and the subthreshold swing voltage were ∼ 106, 0.96 cm2 V s, and 1.39 V /decade, respectively.