Top-Down Approaches for 10 nm-Scale Nanochannel: Toward Exceptional H₂S Detection

Metal oxide semiconductors (MOS) have proven to be most powerful sensing materials to detect hydrogen sulfide (H₂S), achieving part per billion (ppb) level sensitivity and selectivity. However, there has not been a way of extending this approach to the top-down H₂S sensor fabrication process, completely limiting their commercial-level productions. In this study, we developed a top-down lithographic process of a 10 nm-scale SnO₂ nanochannel for H₂S sensor production. Due to high-resolution (15 nm thickness) and high aspect ratio (>20) structures, the nanochannel exhibited highly sensitive H₂S detection performances (R_a/R_g = 116.62, τ_res = 31 s at 0.5 ppm) with selectivity (R_H/R_acetone = 23 against 5 ppm acetone). In addition, we demonstrated that the nanochannel could be efficiently sensitized with the p-n heterojunction without any postmodification or an additional process during one-step lithography. As an example, we demonstrated that the H₂S sensor performance can be drastically enhanced with the NiO nanoheterojunction (R_a/R_g = 166.2, τ_res = 21 s at 0.5 ppm), showing the highest range of sensitivity demonstrated to date for state-of-the-art H₂S sensors. These results in total constitute a high-throughput fabrication platform to commercialize the H₂S sensor that can accelerate the development time and interface in real-life situations.