Dense and uniform NiO thin films fabricated by one-step electrostatic spray deposition

• Dense and uniform NiO thin films were obtained using ESD process.
• The (1 0 0) preferred orientation of NiO films was controlled by solvent system.
• Microstructural, electrical and optical properties were improved by annealing.
• NiO films showed high conductivity and long-term stability at high temperature.
• After annealing, the resulting films were still dense and crack-free.

NiO thin films were prepared using one-step electrostatic spray deposition without additives. Dense and crack-free NiO films with (1 1 1) preferred orientation could easily be obtained by tailoring the solvent system in a precursor solution and the annealing temperature. To reduce the evaporation during the deposition and to allow a better spreading of the droplets on the substrate, a mixture of ethanol and butyl carbitol was used as a solvent. The films deposited using the mixed solvent system showed a much smoother and denser surface compared with those deposited using ethanol. The structural parameters, oxygen/nitrogen atomic ratio, electrical conductivity and optical transmittance were improved as the annealing temperature increased in the range of 400–800 °C. Furthermore, the resistance of NiO film remained constant over time at each measurement temperature for 5 h for stability test by heating and cooling process between 200 and 300 °C.