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

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 × 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 × 10
¹⁸
cm
^-3
) is significantly higher than that of ZnO (2 × 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.