Defect-passivated InGaZnO/In2O3 stacked thin-film transistors with visible-light-assisted recovery for room-temperature ppb-level NO2 detection†

Abstract

The hierarchical stacking of oxide semiconductors presents a transformative strategy to address intrinsic defect limitations in amorphous metal oxide semiconductor (MOS)-based thin-film transistors (TFTs). Although conventional MOS-TFTs suffer from high defect densities that degrade carrier mobility and operational stability, the engineered stacking of InGaZnO (IGZO)/In₂O₃ bilayer TFTs demonstrates synergistic electrical and gas sensing enhancements. Fabricated via room-temperature RF magnetron sputtering, the IGZO/In₂O₃ TFTs exhibit superior electrical performance, including a near-zero threshold voltage (≈0 V), enhanced output current density, and reduced hysteresis, which is attributed to the defect passivation mechanism at the interface. These advancements enable low-power, high-stability gas sensors with amplified response signals. Crucially, the IGZO/In₂O₃ TFTs enable dual-mode optical recovery. Visible-light activation replaces UV irradiation, and achieves efficient sensor recovery while maintaining safety and energy efficiency, something unattainable with single-layer In₂O₃ TFTs. The stacked layers further ensure exceptional NO₂ selectivity towards 50 ppb detection in the temperature range of 25–100 °C and long-term stability, outperforming conventional high-temperature operating MOS gas sensors. Furthermore, this work has the potential to empower forensic science with on-site rapid detection capabilities for trace gaseous evidence, enabling real-time capture and digital evidence archiving of critical targets such as explosive residues and narcotic volatiles through ppb-level sensitivity, visible-light-activated recovery at room temperature, and portability.