Rapid and wide-range detection of NO <sub/>x</sub> gas by N-hyperdoped silicon with the assistance of a photovoltaic self-powered sensing mode

摘要： Wide dynamic range NOx sensors are vital for environment and health purposes, but few sensors could achieve wide range detection with ultralow and ultrahigh concentrations at the same time. In this article, the microstructured and nitrogen-hyperdoped silicon (N-Si) for NOx gas sensing is investigated systematically. Working by the change of surface conductivity, the sensor is ultra-sensitive to low concentration of NOx down to 11 ppb, and shows a rapid response/recovery time of 22/33 s for 80 ppb. When NOx concentration increases and exceeds a threshold value (10–50 ppm), an n–p conduction type transition is observed due to the inversion of the conduction type of major carriers, which limits the sensor’s dynamic range at high concentration. However, when the sensor works in a photovoltaic self-powered mode under the asymmetric light illumination (ALI), the limitation can be successfully overcome. Therefore, with the combination of the two working principles, a wide dynamic range stretching over six orders of magnitude (~0.011–4,000 ppm) can be achieved.