Humidity enhanced ammonia gas sensing by Ga2O3/MWCNT at room

Gallium oxide (Ga2O3) and multi -walled carbon nanotubes (MWCNT) were synthesized by hydrothermal and chemical vapor deposition (CVD) techniques respectively. The physical method is adopted to obtain the composite of Ga2O3/MWCNTs with varying concentration of MWCNT. The Ga2O3/MWCNT is characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Raman spectroscopy. XRD revealed the monoclinic crystallite structure of the pristine beta-Ga2O3 and amorphous nature of MWCNT. The micrographs of powder samples obtained from FESEM investigations revealed cocoon shape morphology for pristine beta-Ga2O3 and nanotube structure for MWCNT. Raman spectra showed the distinctive peaks of monoclinic Ga2O3 and MWCNT which confirms the presence of both the components in the composites. The Ga2O3/MWCNT nanocomposite with different concentration of MWCNT was exposed to different gases to study the response at different humidity. The sensing results at room temperature showed that the obtained sensor with Ga2O3 and 5 wt% MWCNT exhibits maximum current response around 500% with 50 ppm NH3 at RH 56% and can detect as low as 2 ppm with 10% current response. Enhancement in the sensing was ascribed to the synergetic effect of the p -p junction between MWCNT and Ga2O3 surface's inversion layer due to adsorbed water vapor in ambient air. The developed sensors demonstrated good selectivity, quick response time of 46.11 s and recovery of 34.48 s for 50 ppm of NH3.