Gas sensing performance of GaOOH and β-Ga2O3 synthesized by hydrothermal method: a comparison

Gallium Oxy Hydrate (GaOOH) and β-Ga2O3 nanostructures in submicron scale have been synthesized at low temperature by surfactant-free hydro-thermal method. First, GaOOH has been synthesized using Gallium nitrate anhydrate, Ammonium hydroxide as precursors and double distilled water as solvent. As obtained GaOOH powders have been converted into α-Gallium Oxide (α-Ga2O3) and β-Gallium Oxide (β-Ga2O3) powders by calcination at 400 °C and 900 °C, respectively. The GaOOH and β-Ga2O3 powders have been characterized by XRD, FE–SEM, UV–VIS, Thermo Gravimetric Analysis, I-V characteristics and BET surface analysis in order to reveal their structural, morphological, optical, thermal, electrical and surface properties. FE-SEM micrographs confirm the rod like and needle like morphologies of GaOOH and β- Ga2O3 samples, respectively. Porous nature of the samples observed through BET and BJH analyses. Synthesized GaOOH and β-Ga2O3 powders have been subjected to room temperature CO2 gas sensing in the range, 2000 ppm – 10 000 ppm. β-Ga2O3 showed enhanced CO2 sensing response than that of GaOOH due to its better structural, electrical, morphological and surface properties. GaOOH showed quick response of 80 s and fast recovery of 129 s at 8000 ppm while β-Ga2O3 showed quick response of 52 s at 8000 ppm and faster recovery of 98 s at 4000 ppm. Also, the repeatability studies were done for GaOOH and β-Ga2O3 films by exposing to different CO2 concentrations for a period of 6 consecutive days.