Influence of nitrogen dopant source on the structural, photoluminescence and electrical properties of ZnO thin films deposited by pulsed spray pyrolysis

The N-doped ZnO thin films have been deposited using pulsed spray pyrolysis from Zinc Acetate (ZA) precursor along with the N dopants of N₂ carrier gas (N2 – series) and Ammonium Acetate (AA – series) on glass substrates at the optimized substrate temperature of 300 °C with different spraying pulse intervals. The X-ray powder diffraction studies confirmed the polycrystalline structures with the presence of mixed compressive and tensile strain along ‘a’ and ‘c-axes’ respectively for the N₂ doped films and the presence of compressive strain alone along both ‘a’ and ‘c-axes’ for the AA doped films. The XPS analysis revealed that the N₂ gas source led to the incorporation of elemental N into the film and the AA source led to the incorporation of both elemental and molecular N into the film. The Micro Raman Analysis confirmed the N-doping and its contributed carrier localization by exhibiting A₁(LO) and A₁(TO) modes. Photoluminescence studies exhibited the active band gap of ~3.19 eV with additional peaks related to hole traps at ~3 eV and electron traps at ~2.8 eV without exhibiting peaks correspond to oxygen vacancy defects. The Seebeck measurements confirmed the establishment of intrinsic p-type conductivity in both the cases at room temperature (RT) and the films deposited with pure elemental doping from N₂ source found exhibiting better p-type conductivity than those films deposited using AA source.