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

Abstract

To enhance the performance of semiconducting metal oxides, as hydrogen (H-2) sensor, we introduced a high carrier concentration (N-d) metal oxide, indium-gallium-zinc oxide (IGZO), combined with palladium (Pd) catalysis. This allowed the detection of low concentrations of H-2 at room temperature. The base current level was linearly increased with the Pd thickness. As a result, a high sensor sensitivity of 6.1 x 10(6)% at 5% H-2 concentration 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 x 10(18) cm(-3)) is significantly higher than that of ZnO (2 x 10(16) cm(-3)), indicating a closer location for the Fermi level of IGZO to the conduction band. Therefore, a relatively small amount of electron-donating H-2 was 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 H-2 concentrations.