Chemiresistive sensing is one of the most promising technologies for next-generation chemical sensor, with applications ranging from air quality monitoring to explosive detection, healthcare and the fast-developing Internet of Things (IoT). Recently, there have been growing efforts in developing room temperature chemiresistive sensors with high sensitivity, selectivity, long-term stability, and low power consumption. 

In this seminar, I will present my research on the design, fabrication and characterization of indium phosphide (InP) nanowire (NW) array based nitrogen dioxide (NO2) chemiresistive sensors for air pollutant monitoring. By carefully engineering the NW geometry (i.e., diameter and pitch), this sensor obtains a superior sensitivity, limit of detection 3.1 ppb at room temperature, with outstanding selectivity and long-term stability. Kinetic analysis and electrical simulation further reveal the array geometry correlated sensing mechanism. To minimize the device power consumption, a novel photovoltaic (PV) self-powered NO2 sensor is further designed based on InP NWs with axial p-i-n homojunction. We have demonstrated that based on numerical simulation optimization, the PV InP NW array device can be designed and fabricated to achieve 84% sensing response to 1 ppm NO2 with a record limit of detection down to sub-ppb level even under <5% of 1 sun illumination. With this great atmosphere light fidelity, the sensor is integrated onto a commercial microchip interface for dynamic self-powered monitoring of on-field motor vehicle exhaust. 

Not only for oxidizing gas such as NO2, we have further revealed that by applying surface-modification, the InP NW array can also be fabricated into chemical sensors highly sensitive to reducing gases such as acetone, which is critical for the development of breath ketone sensors for diabetes diagnostic and monitoring. Our research indicates that, III-V compound semiconductor NW array presents a promising chemical sensing platform for development of high performance, miniaturized, low power consumption, multiplexing on-chip sensing system for large-scale implementation of IoT technology.