Electrical Performance and Stability Improvement of In₂O₃ Thin-Film Transistors Engendered by Oxygen-Free Focused Plasma Treatment

In the last decade, interest in solution-processed transparent oxide semiconductors has been increasing. Specifically, indium oxide (In₂O₃) films have been researched due to their processability using aqueous solutions without organic additives. However, the film quality of as-deposited layers might be suboptimal, which requires some type of post-deposition treatment. In this work, the effect of the treatment by a focused plasma (FP) under both N₂ (FP-N) and N₂:H₂ (FP-H) gases on In₂O₃ thin-film transistors (TFTs) is explored. The In₂O₃ TFTs with optimized device performance were fabricated using a volatile nitrate precursor at an annealing temperature of 250 °C. The FP-N In₂O₃ devices achieved saturation mobility (µ_sat) of 3.83 ± 0.14 cm²/Vs, and the threshold voltage was about 3 V. The FP-H devices with a µ_sat of 2.56 ± 0.15 cm²/Vs, on/off current ratio of 4.3 × 10⁶, exhibited stable electrical characteristics with improved gate bias stress stability and time-dependent environmental stability. These results demonstrate that FP treatment of solution processed In₂O₃ semiconductors effectively enhances carrier transport performance and improves bias stability.