Precursor Molarity Effect on the Ammonia Gas Sensing of Transparent Conductive Tin Oxide Thin Films at Room Temperature

ABSTRACT

SnO ₂ ‐based gas sensors are widely studied for hazardous gas detection due to their high sensitivity and stability; however, their practical application is often restricted by high operating temperatures. In this work, SnO ₂ thin films with different precursor molarities (0.05, 0.1, 0.25, and 0.5 

) were prepared using the sol–gel spin coating technique and annealed at 500°C for 1 h in ambient air to investigate their room‐temperature NH ₃ sensing performance. XRD analysis confirmed the formation of polycrystalline tetragonal rutile SnO ₂ thin films, while FE‐SEM studies revealed denser morphology and increased thickness with increasing molarity. Gas sensing measurements performed at NH ₃ concentrations of 100–500 ppm demonstrated that the 0.5  SnO ₂ thin film exhibited the highest sensing response of 49.2 at 500 ppm, along with rapid response and recovery behavior at room temperature (30°C). The enhanced sensing performance is attributed to increased surface activity and adsorption sites in the high‐molarity films. The results demonstrate that precursor concentration strongly influences the structure–property relationship and sensing behavior of SnO ₂ thin films, highlighting their potential for low‐cost and energy‐efficient room‐temperature ammonia sensing applications.