A comparison study on hydrogen sensing performance of Pt/MoO3 nanoplatelets coated with a thin layer of Ta2O5 or La2O3

In this work, we investigate how hydrogen sensing performance of thermally evaporated MoO₃ nano-platelets can be further improved by RF sputtering a thin layer of tantalum oxide (Ta₂O₅) or lanthanum oxide (La₂O₃). We show that dissociated hydrogen atoms cause the thin film layer to be polarised, inducing a measurable potential difference greater than that as reported previously. We attribute these observations to the presence of numerous traps in the thin layer; their states allow a stronger trapping of charge at the Pt-thin film oxide interface as compared to the MoO₃ sensors without the coating. Under exposure to H₂ (10 000 ppm), the maximum change in dielectric constant is 45.6 (at 260 °C) for the Ta₂O₅/MoO₃ nanoplatelets and 31.6 (at 220 °C) for the La₂O₃/MoO₃ nano-platelets. Subsequently, the maximum sensitivity for the Ta₂O₅/MoO₃ and La₂O₃/MoO₃ based sensors is 16.8 and 7.5, respectively.