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.