Rapid and Wide-Range Detection of NO<i>_x</i> Gas by N-Hyperdoped Silicon with the Assistance of a Photovoltaic Self-Powered Sensing Mode

Abstract

Wide-dynamic-range NO<i>_x</i> sensors are vital for the 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 NO<i>_x</i> gas sensing is investigated systematically. Working by the change of surface conductivity, the sensor is ultrasensitive to low concentrations of NO<i>_x</i> down to 11 ppb and shows a rapid response/recovery time of 22/33 s for 80 ppb. When the NO<i>_x</i> 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 dynamic range of the sensor at high concentration. However, when the sensor works in a photovoltaic self-powered mode under the asymmetric light illumination, the limitation can be successfully overcome. Therefore, with the combination of the two working principles, a wide dynamic range stretching over 6 orders of magnitude (∼0.011-4000 ppm) can be achieved.