Effect of oxygen plasma treatment on p-type electrical properties of amorphous La₂NiO_4+δ thin films

La₂NiO₂NiO_4+δ shows a p-type electrical conductivity, due to the incorporation of oxygen ions (δ) in its lattice. In the present study, amorphous La₂NiO₂NiO_4+δ thin films were fabricated by radio frequency (RF) magnetron sputtering. To investigate the effect of oxygen plasma treatment on the electrical properties of La₂NiO₂NiO_4+δ thin films, the films were exposed to oxygen plasma for varying times. The as-deposited films at room temperature exhibit an increase in carrier concentration from 6.20× 1013 cm^-3 to 4.61×10¹⁴ cm^-3 after a 60-minute exposure to oxygen plasma. On the basis of the XPS spectra analysis, the binding energies of oxygen and nickel ions were found to be shifted towards higher energies, indicating an increase in the oxidation states of the cations.