Veronica Arriaga Rose Hills
Gas Sensors: Identifying Electrical and Chemical Degradation Mechanisms
Chemiresistive sensors detect gas concentrations based on the change in resistance of a sensing material, providing low-cost detection in applications such as environmental monitoring. SnO2 is an industry-standard material system for chemiresistive sensing. SnO2-based sensors typically have high baseline resistance and slow dynamics at room temperature, and thus require on-board heaters to improve their sensitivity and response time. Although heating greatly improves the response of SnO2-based sensors, prolonged operation at requisite temperatures (200–300°C) results in baseline drift and changes in sensitivity over time. Such degradation is observed even in commercial SnO2-based sensors and is an open problem in chemical sensing. I propose to identify and characterize the mechanisms that underlie the degradation of SnO2-based sensors. Although the general mechanisms that govern how SnO2 responds to ambient gases, such as O2 and volatile organic compounds, have been studied, a definitive analysis that links the degradation of the electrical (i.e., chemiresistive) performance of SnO2-based sensors to changes in the chemical properties of SnO2 itself is lacking.