Optimization of trade-off between mobile carriers and surface defects for enhanced H₂S sensing in SnO₂-decorated In₂O₃ nanocomposites via two-step temperature and pressure control

SnO₂-decorated In₂O₃ nanocomposites that feature nanoleaf-like SnO₂ grown on In₂O₃ nanocubes via a surface-wrapping mechanism were synthesized using two consecutive hydrothermal methods. These samples exhibited an unusual temperature-dependent response to H₂S gas (150 °C > 200 °C > 100 °C > 250 °C), which contrasts with the typical behavior of semiconductor gas sensors. This nonlinear trend is attributed to the dominance of different sensing mechanisms: an oxygen vacancy-controlled mode between 100 and 150 °C and a majority carrier-controlled mode between 200 and 250 °C. The results highlight the importance of balancing the trade-off between operating temperature and surface-defect concentration to enhance gas sensing.