Effect of pH dependent morphology on room temperature NH3 sensing performances of β-Ga2O3

Abstract

— β-Ga2O3 powders were synthesized by hydrothermal method at different pH values ranging from 5 to 14. Obtained powder samples, showed polycrystalline nature and monoclinic crystalline structure upon investigation through XRD. The micrographs of powder samples resulted from SEM investigations showed different morphologies ranging from basic to hierarchical structures as pH value changes. Extremely alkaline solution (with pH = 14) caused to yield hierarchical morphologies whereas the acidic solution (with pH = 5) ensued basic rod-like morphologies. Cocoon shaped morphology was maintained from neutral (pH = 7) to moderately basic (pH = 11) conditions. Optical band gaps of the samples were calculated from Kubelka-Munk plot resulted from the data obtained by UV–Visible spectroscopic analysis. Synthesized β-Ga2O3 powder samples were drop casted on glass substrate which was pre-printed with Inter Digitated Electrode pattern (IDE) of Silver (Ag) ink. These drop coated thick films are then used for the different concentrations of NH3 vapor detection at room temperature. Morphology based model proposed for room temperature NH3 sensing. It has been observed that β-Ga2O3 prepared under pH = 14 showed higher response and sensitivity due to its hierarchy in morphology and relatively lower band gap of 4.61 eV.