Low-Temperature Ammonia Sensing Using Sulfurized WS₂ Thin Films

This study addresses key challenges in gas sensing, particularly achieving high sensitivity at low operating temperatures. Tungsten disulfide (WS₂) thin films were deposited by sputtering and sulfurized at 800 °C for 30 and 60 min on quartz and sapphire substrates. Raman spectroscopy confirmed multilayer WS₂ formation, with characteristic modes at 349 and 417 cm^-1. X-ray diffraction revealed that the films are polycrystalline with the formation of the hexagonal 2H-WS₂ phase on both substrates. FESEM images showed clearly visible nanoparticles, but they were not evenly distributed and were differently oriented, with a hint of texturing. The WS₂ films exhibited stable sensing performance at low operating temperatures from 30 to 150 °C and high sensitivity toward NH₃ in the 10-200 ppm range. Experimental results indicate a limit of detection, highlighting the potential of WS₂ films for low operating temperature ammonia sensing. A minimum value of the limit of detection of 0.6 ppm for an operating temperature of 150 °C was achieved for the WS₂ sample sulfurized at 800 °C for 60 min on a quartz substrate.