Ultra-High Sensitivity to Low Hydrogen Gas Concentration With Pd-Decorated IGZO Film

To enhance the performance of semiconducting metal oxides, as hydrogen (H2) sensor, we introduced a high carrier concentration (Nd) metal oxide, indium- gallium-zinc oxide (IGZO), combined with palladium (Pd) catalysis. This allowed the detection of low concentrations of H2at room temperature. The base current level was linearly increased with the Pd thickness. As a result, a high sensor sensitivity of 6.1 × 106% at 5% H2concentration was obtained using a 1-nm-thick Pd-decorated IGZO film. Comparative studies with a zinc oxide (ZnO) counterpart showed that the Nd of IGZO (8 × 1018cm-3) is significantly higher than that of ZnO (2 × 1016cm-3), indicating a closer location for the Fermi level of IGZO to the conduction band. Therefore, a relatively small amount of electron-donating H2was required to overcome the energy barrier in IGZO. Consequently, the 1-nm-thick Pd-decorated IGZO sensor responded to a gas level as low as 0.01% (100 ppm) and demonstrated a 70-fold higher sensitivity compared with ZnO sensor at all H2concentrations.