Study of hetero-structure for improved sensitivity of self-heating type gas sensor

Abstract

Self-heating type gas sensors have become promising gas sensors for mobile application. Because self-heating type gas sensors are able to reach their operating temperature without the need of an external heater, they are able to achieve small size and low power consumption. However, during self-heating operation, heat loss through the substrate causes a parabolic temperature distribution, resulting in only the center portion of the metal-oxide sensing material to reach the operating temperature and participate in the gas reaction. This paper resolves the issue by proposing a novel hetero-structure that consists of metal – metal-oxide – metal nanowires that enables the entire sensing material to reach its operating temperature. Instead of connecting directly to the electrode, the metal nanowires are connected in between the metal-oxide nanowires and the electrode. This hetero-structure utilizes the metal nanowires, which have low thermal conductivity and smaller heat loss area, to preserve the heat and minimize the heat loss. The proposed structure is able to achieve improved sensitivity, low power consumption, and fast response time to hydrogen gas. Through metal functionalization of the sensing material, further enhancement in sensitivity would be achievable.