Dielectric barrier discharge plasma enhances room-temperature ammonia sensing in ZnO thin films for rapid environmental monitoring

Zinc oxide (ZnO) thin films are widely explored for gas sensing due to their low cost, stability, and intrinsic sensitivity, yet their room-temperature performance is often limited by slow sensing response, poor selectivity, and insufficient active sites. This study reports a scalable strategy to enhance ammonia sensing via dielectric barrier discharge (DBD) plasma treatment of spin-coated ZnO films. Plasma exposure for 6 min (ZnO@P6) significantly tailored structural, morphological, optical, and surface chemical properties compared to pristine ZnO. X-ray diffraction and scanning electron microscopy analyses revealed reduced crystallite size and enhanced lattice strain, while Brunauer-Emmett-Teller and Barrett-Joyner-Halenda measurements showed increased surface area (90 m2 g−1) and enlarged mesopores (~5.94 nm). X-ray photoelectron spectroscopy confirmed oxygen-vacancy formation, nitrogen incorporation, while electron paramagnetic resonance spectra demonstrated a strong signal at g = 1.965, indicating abundant paramagnetic oxygen vacancies that act as shallow donors to enhance charge transport and surface reactivity. Optical studies revealed bandgaps narrowing to 3.206 eV, and water contact angle measurements confirmed improved hydrophilicity. ZnO@P6 exhibited ultralow detection limits (1 ppm), rapid response/recovery times (6 s/53 s), and a high sensing response of 2925 at 800 ppm NH3, markedly outperforming pristine ZnO (sensing response 609 at 800 ppm). Density functional theory simulations corroborated strong NH3 chemisorption (−0.94 eV) with significant charge redistribution. These results demonstrate that DBD plasma engineering produces defect-rich, high-surface-area ZnO films, providing a robust platform for high-performance, selective, and stable room-temperature ammonia sensing for environmental monitoring.