Silicon nanowire-based ammonia gas sensor with enhanced response at elevated humidity levels

Abstract Ammonia (NH 3 ) is a corrosive and toxic gas to which exposure can cause serious health problems and even death. Elevated levels of it in exhaled breath can serve as a biomarker for various diseases. Consequently, monitoring NH 3 in the ambient air and for medical diagnostics is important for public health and safety. However, developing NH 3 gas sensors that function effectively in high humidity conditions, such as those found in human breath, has proven challenging. In this study, we present a simple and cost-effective NH 3 gas-sensor based on a structure of interconnected silicon nanwires (SiNWs), fabricated with metal-assisted chemical etching. Two different versions were made and compared; SiNWs, with and without germanium nanoparticles. The sensing mechanism is attributed to the formation of a hole accumulation layer in the air, whose width decreases upon exposure to NH 3 . It was also observed that bundling of individual nanowires enhances the sensor’s response time, down to approximately 70 s, which is an order of magnitude faster response than that of similar SiNW structures reported in the literature.