Boron-doped diamond as a functional semiconductive layer in chemiresistive sensors for the enhanced gas sensing of NO2 at room temperature

Nowadays chemiresistive gas sensors are viewed as fast, accurate, cheap, and effective instruments to monitor various hazardous air pollutants. However, most sensing materials currently used in such gas sensors require an activation step, in terms of additional thermal energy supplied to the sensing material, to achieve the necessary interaction between the sensing surface and the target gas molecule. In this work, the application of nanocrystalline boron-doped diamond (BDD) as the active layer/component in a chemiresistive gas sensor was investigated, focusing on the room-temperature operation of the gas sensor in the presence of oxidizing (NO2, CO) and reducing (NH3) gases. In contrast to previous reports using nanocrystalline diamond (NCD) as a gas sensing layer, the utilization of BDD layer eliminates the need for a precise control of the diamond layer surface hydrogen-termination, since BDD layer inherently exhibits p-type bulk semiconductive characteristics due to the presence of boron atoms. To enhance the sensitivity of the gas sensors based on BDD during room-temperature operation, a sensor comprised of BDD and Pd-SnO2 layer in the form of a BDD/Pd-SnO2 heterostructure was fabricated and investigated. The hybrid BDD/Pd-SnO2 sensor exhibited an improved response in the presence of oxidizing NO2 gas when compared to BDD-based sensors, and its sensitivity and recovery characteristics were further enhanced upon photo-assisted (illumination with UV) gas sensing, demonstrating the potential of BDD-based hybrid/heterojunction structures as a platform for the construction of gas sensors operating at room-temperature.