Preparation Of Metal Oxide Thin Films By Low Temperature Solution Method And Its Application In Thin Film Transistors

Over the past decade,oxide semiconductor-based thin-film transistors?TFTs?have become the key components in flat-panel displays because of their excellent electrical performance,large-area uniformity,and high transparency in visible range.Several prototype displays driven by oxide semiconductor TFTs have been developed.With the rapidly rising demands for cost-effective and large-area electronics,the solution-based deposition methods have emerged as the more competitive candidate due to the simplicity,low cost,large-area device uniformity,and atmosphere manufacturing.This thesis focuses on the investigation of solution-processed metal-oxide semiconductor/insulator and explores their applications in TFTs.Three chapters are involved in this thesis.1.The ZrO₂ dielectric thin films with high permittivity?high-k?were fabricated using solution process.By using the UV-assisted photochemical activation,the undesired residues could be decomposed at temperatures lower than 150 oC,achieving the high-quality high-k dielectric films with low leakage current and high capacitance.By using ZrO₂ as the dielectric layer,we further investigate the effect of annealing temperature on the electrical properties of In₂O₃ TFTs.The result indicate that the optimized In₂O₃/ZrO₂ TFT exhibits high field-effect mobility and large on/off current ratio at an ultra-low voltage.This work makes significant achievement for the development portable,low-consumption,and battery-driven devices.2.We investigate the fabrication of low-voltage and high-performance TFTs using water-inducement method.Its precursor solution only contains water and metal nitrates.Compared with the conventional organic-based synthesis route,water-inducement method owns the low-temperature and eco-friendly characteristics.We fabricated the water-induced InZnO semiconducting and Y2O3 high-k dielectric films.The effects of annealing temperature and annealing time on the device performance were investigated systematically.Through prolonging the annealing time at low temperatures,the electrical parameters of water-induced oxide TFTs are comparable with the devices annealed at higher temperatures.3.The solution-processed p-type NiO TFTs were fabricated and investigated.After consulting the literatures carefully,it is found that the main research works on metal-oxide semiconductors are focused on the n-type materials.This is not beneficial to the development of p-n junction and complementary metal-oxide semiconductor-based circuits where both n-and p-type oxides are needed.By dissoving nickel acetate tetrahydrate and monoethanolamine in ethanol,we investigated the effect of annealing temperature on the film properties.The p-type NiO semiconducting films with smooth surface morphology,high optical transparency,and amorphous nature were obtained at 250 oC annealing condition.By integrating the obtained NiO films into TFTs,the devices exhibited a hole mobility of 0.07 cm2/Vs and a large on/off current ratio of 4×104.