Ammonia gas sensing properties of Al doped ZnO thin films

Abstract

Aluminium (Al)-doped ZnO thin films are synthesised by chemical spray pyrolysis technique and investigated their gas sensing properties. X-ray diffraction analysis of the films revealed the formation of hexagonal-phase (wurtzite) of ZnO with orientation along (002) plane. Interestingly, the lattice parameters of Al-doped ZnO films showed a decreasing trend with Al doping, suggesting incorporation of Al in the crystal lattice of ZnO. A significant change in both the volume of the unit cell and bond length with an increase in Al concentration is observed. The surface morphological analysis suggested the formation of hexagonal-like ZnO, which transform into spherical particles with Al doping. The energy dispersive spectra confirm the existence of Al, Zn and O. The optical absorption analysis showed that the bandgap of ZnO samples decreases from 3.28 eV to 3.21 eV with Al content in ZnO. The ammonia gas sensing properties of ZnO and Al-doped ZnO are studied at 25 ppm concentration of ammonia gas in air at 100 °C temperature, suggesting reasonable gas sensing characteristics.