Impact of humidity on hydrothermally synthesised gallium oxide nanoparticles for ammonia gas sensing at room temperature

The GaOOH powders were synthesized by hydrothermal method using Gallium Nitrate Hydrate (Ga (NO₃)₃·xH₂O) as precursor at 120 °C. Obtained product is calcinated at 1000 °C to get β-Gallium Oxide (β-Ga₂O₃). The resulting product is studied utilising a variety of characterisation methods, including UV–Vis spectroscopy, SEM, XRD, BET analysis and XPS. Following XRD analysis, the powder samples revealed polycrystalline nature and monoclinic crystalline structure. The micrographs of powder samples resulted from SEM displayed uniformly synthesized rhombohedral morphology. Surface area and the pore size distribution were found from BET analysis. A surface-sensitive method XPS was used to confirm the chemical states and their fundamental components of the synthesized Ga₂O₃ material. The evaporation process was used to pre-deposit glass substrate with an Inter Digitated Electrode pattern (IDE) of silver (Ag) before casting samples of synthesised β-Ga₂O₃ powder. At room temperature, the various amounts of ammonia (NH₃) vapour were detected using these drop-coated thick films at various humidity levels. Films were sensitive to NH₃ gas and marked a response of 160 % with quick response and recovery time of 42 s and 30 s respectively for 100 ppm. It can sense as low as 10 ppm of NH₃ with response of 11 % at room temperature (RT) under 69 % relative humidity (RH).