Insight into the Humidity Dependent Pseudo-n-Type Response of p-CuScO2 toward Ammonia.

Metal oxide semiconductor (MOS) gas sensors operated at room temperature (RT) hold great promise for environmental monitoring in the emerging smart society. An in-depth understanding of the gas/MOS interfacial charge exchange under the ambient moist atmosphere is essential for subsequent molecule recognition. Herein, delafossite p-CuScO2 with a unique oxygen intercalation property was utilized. Eight orders of resistance tuning could be rationally achieved via controlling oxygen intercalation realized by air annealing (without altering the size and morphological properties), which allows extraction of both the intrinsic (gas/MOS interaction, p-type response) and extrinsic (gas/H2O/MOS interaction, pseudo-n-type response) sensing mechanisms upon exposure to ammonia molecules. This work could provide an insight into the underlying sensing mechanism of RT sensors working in an ambient moist atmosphere, and the unique n- to p-type switching contains rich molecule related features that could be potentially explored for molecule recognition.