Ultrasensitive Detection of VOCs Using a High-Resolution CuO/Cu2O/Ag Nanopattern Sensor

The p-type semiconducting copper oxides (CuO and Cu2O) 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/Cu2O nanopattern channels. The high-resolution CuO/Cu2O/Ag nanochannel is fabricated using a unique top-down nanolithographic approach. The gas response (Delta R/R-a) of the CuO/Cu2O/Ag gas sensor increases by a maximum factor of 7.3 for various volatile organic compounds compared with a pristine CuO/Cu2O gas sensor. The sensors exhibit remarkable sensitivity (Delta R/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 (approximate to 30 nm), high aspect ratio (approximate to 12), and ultrasmall grain boundaries (approximate to 10 nm) of the CuO/Cu2O nanopatterns and ii) the electronic sensitization and chemical sensitization effects induced by incorporating Ag nanoparticles on the CuO/Cu2O channels.