SnS/SnS2p-n heterojunctions: accumulation layer-driven rapid and highly sensitive ethanol detection at room temperature.

Designing 2D heterostructures allows for a strong approach for enhancing the sensing performance of layered materials in an efficient way, fully utilizing the better quality of their heterointerfaces. The tremendous potential of 2D heterointerfaces for gas sensing remains largely untapped as very few attempts have been made to strike this highly promising frontier. This work focuses on an ultrasensitive and fully recoverable ethanol gas sensor featuring SnS/SnS₂p-n heterojunctions that operate effectively at room temperature (RT). The SnS/SnS₂heterostructure is found to enhance the response (R_g/R_a) by a factor of 1.8 times that of pristine-SnS, having rapid response and recovery times of 6.1 sec (s) and 18.3 s to 500 ppm ethanol at RT. The SnS/SnS₂nanocomposite shows excellent stability of over 40 d, with superior reproducibility and selectivity, ensuring robust sensing performance with relatively minimal impact from relative humidity. The observed improvement can be primarily attributed to optimal electronic band alignment and specific synergistic properties of nanomaterials. The enhanced sensing performance results from improved electron transport, increased adsorption sites, and effective electron transfer from SnS to SnS₂in the p-n heterojunctions. The present work also proposes novel insights in terms of the strategic design of chemical sensing devices and exploits the synergies based on p-n heterostructures with an electron accumulation layer.