Ultrasensitive Detection of VOCs Using a High-Resolution CuO/Cu ₂ O/Ag Nanopattern Sensor

The p-type semiconducting copper oxides (CuO and Cu ₂ O) are promising materials for gas sensors, owing to their characteristic oxygen adsorption properties and low operation temperature. In this study, the sensing performance of a CuO-based chemiresistor is significantly enhanced by incorporating Ag nanoparticles on high-resolution p-type CuO/Cu ₂ O nanopattern channels. The high-resolution CuO/Cu ₂ O/Ag nanochannel is fabricated using a unique top-down nanolithographic approach. The gas response (ΔR/R _a ) of the CuO/Cu ₂ O/Ag gas sensor increases by a maximum factor of 7.3 for various volatile organic compounds compared with a pristine CuO/Cu ₂ O gas sensor. The sensors exhibit remarkable sensitivity (ΔR/R _a = 8.04) at 125 parts per billion (ppb) for acetone analytes. As far as it is known, this is the highest sensitivity achieved for p-type metal oxide semiconductor (MOS)-based gas sensors compared to previous studies. Furthermore, the outstanding gas responses observed in this study are superior to the most of n-type MOS-based gas sensors. The high sensitivity of the sensor is attributed to i) the high resolution (≈30 nm), high aspect ratio (≈12), and ultrasmall grain boundaries (≈10 nm) of the CuO/Cu ₂ O nanopatterns and ii) the electronic sensitization and chemical sensitization effects induced by incorporating Ag nanoparticles on the CuO/Cu ₂ O channels.