Investigation of high-mobility quaternary co-doped indium oxide thin films for low-thermal-budget electronic applications
摘要
Indium tin oxide (ITO) is the standard transparent conductive oxide (TCO) for flat panel displays (FPDs). However, achieving high-performance ITO typically requires annealing above 300 °C, which often compromises the integrity of heat-sensitive components such as indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs) or flexible substrates. To overcome this, multiple titanium groups and rare-earth elements co-doped indium oxide (IMO) films were investigated, processed by post-deposition annealing at low temperatures up to 200 °C. X-ray diffraction (XRD) reveals a transition from an amorphous to a nanocrystalline phase as the annealing temperature rises, and atomic force microscopy (AFM) confirms a smooth surface with a root-mean-square (RMS) roughness below 2 nm. Hall-effect measurements show that the mobility increases from ~ 25 cm2 V−1 s−1 for the as-deposited film to 75 cm2 V−1 s−1 after annealing at 200 °C, while the resistivity decreases to 0.3 mΩ·cm. Optical characterization indicates a visible transmittance higher than 85%, a tunable optical bandgap (3.5–3.7 eV) and favorable optical constants (n ≈ 1.7–2.3, k < 0.04). These results show that the IMO films combine high carrier mobility, low resistivity, high visible transparency and a smooth surface, all obtained by conventional magnetron sputtering with a single low-temperature (≤ 200 °C) annealing step. This balanced performance at a low thermal budget makes the quaternary co-doped films a practical TCO candidate for next-generation flexible display technologies.