Highly responsive gas sensors based on grain boundary–rich polycrystalline few-layer MoS₂ films for NO₂ detection

Abstract This study addresses the issues of insufficient sensitivity and poor reversibility for NO 2 detection by successfully fabricating a sensor based on uniform and high-quality few-layer MoS 2 polycrystalline material using chemical vapor deposition. This approach aims to improve the response of the sensor by exploiting the abundance of grain boundary (GB) defects in polycrystalline MoS 2 membranes. Comprehensive surface morphology analysis of the few-layer MoS 2 polycrystalline films was conducted using microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy to characterize their chemical composition and properties. Subsequently, evaluation of 1–100-ppm NO 2 was conducted at room temperature (25 °C). The results show excellent performance of the sensor, with a response range of 11–82.24. Notably, under ultraviolet excitation at room temperature, this sensor exhibits a response time of only 41 s to 50 ppm of NO 2 with complete recovery and improved sensitivity, maintaining reliable stability over eight weeks. Furthermore, the findings reveal that the sensor demonstrates high selectivity toward NO 2 gas with limit of detection and limit of qualification values of 10 and 34 ppb, respectively. Owing to the abundant adsorption sites provided by GB defects in polycrystalline thin films, the response performance of the sensor is effectively enhanced. This study provides valuable insights into the future design and development of high-performance NO 2 gas sensors.