Cross-linked structure of self-aligned p-type SnS nanoplates for highly sensitive NO2 detection at room temperature

Morphological engineering of two-dimensional chalcogenides has led to significant advances in terms of high responses and low power consumption for chemiresistive gas sensors. Nevertheless, the practical use of such nanostructured two-dimensional materials is still limited. The difficulties in patterning resulting from the morphological complexity of nanostructures and the absence of highly sensitive p-type semiconductor sensors are major obstacles. In this study, we report a highly sensitive NO2 gas sensor composed of cross-linked p-type SnS nanoplates on SiO2 nanorods. The area-selective growth of SnS by atomic layer deposition allows for the self-aligned formation of SnS nanoplates only on SiO2 nanorods without an additional patterning process. The cross-linked structure of the SnS nanoplates enabled the electrical connection of small and very thin SnS nanoplates, which increased the resistance difference between the hole accumulation layer across the entire surface and the less conductive core. Consequently, this cross-linked structure enhances the gas response of p-type semiconductor sensors. The gas response did not vary significantly when the relative humidity (RH) changed from 40% to 80%. Under ambient conditions of 60% RH at room temperature, the SnS sensor exhibited a high response of 116% to 5 ppm NO2, along with an extremely low detection limit of 21 ppt. The sensor showed excellent selectivity for NO2, with a minimal response to other gases. This approach provides possibilities for employing p-type semiconductors in practical room-temperature sensor applications.