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 N-2 carrier gas (N2 - series) and Ammonium Acetate (AA - series) on glass substrates at the optimized substrate temperature of 300 degrees 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 N-2 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 N-2 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 A(1)(LO) and A(1)(TO) modes. Photoluminescence studies exhibited the active band gap of similar to 3.19 eV with additional peaks related to hole traps at similar to 3 eV and electron traps at similar to 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 N-2 source found exhibiting better p-type conductivity than those films deposited using AA source.