High-resolution tin oxide nanopattern structure control for ultra-sensitive hydrogen sulfide gas sensor

Abstract

Hydrogen sulfide($H_2S$) is a highly toxic gas that paralyzes the olfactory nerves, but it occurs in many industries. Therefore, it is important to detect the $H_2S$ gas from ppb to ppm level for industrial and safety applications. In this study, the high-resolution $SnO_2$ nanopattern with ultra-small grain size (<15 nm) and high aspect ratio (>20) was made by our unique top-down lithography technique. This $SnO_2$ nanopattern exhibited remarkable sensitivity from 50 ppb to 50 ppm ($R_a/R_g$=116.62, $\tau_{res}$ = 31 s at 0.5 ppm) along with excellent selectivity. Also, without additional processing, this lithography could add any dopants to nanostructure, inducing sensitization effect. Especially, the sensitivity of $H_2S$ was enhanced in NiO-$SnO_2$ ($R_a/R_g$ = 166.2, $\tau_{res}$ = 21 s at 0.5 ppm) due to p-n heterojunction. In addition, the sensitivity of 5 ppm $NO_2$ was improved in NiO-$SnO_2$ ($R_g/R_a$=190.59) compared to $SnO_2$ ($R_g/R_a$=8.72), shown as a dual switching material applicable to both $H_2S$ and $NO_2$ gases. Therefore, this study was able to control the materials involved in the sensitivity and selectivity of the sensor, and confirmed the commercialization potential of the sensor of high-resolution nanopatterns through unique top-down lithography.