Lithium Content and Low-Temperature Conductivity of NiO:Li Films Deposited by Spray Pyrolysis

The objective of this work was to quantify the amount of lithium incorporated into nickel oxide thin films and study its effects on the oxidation state of the elements and on the electrical conductivity of the films. A set of films was deposited on alumina substrate by spray pyrolysis. The lithium to nickel ratio in the sprayed solution, 0, 20, 40, and 60 at.%, determined the amount of lithium incorporated into the films. The lithium concentration was obtained by combined energy recoil detection analysis and Rutherford backscattering. The ratios of lithium to nickel atoms incorporated in the films were 0, 12.9, 27.9, and 46.9%, respectively. These results were confirmed by x-ray photoemission spectroscopy, which was also used to analyze the oxidation state of the atomic species in the samples. When the electrical conductivity of selected samples was studied as a function of temperature in the range 50-450 K, kinked-linear behavior was observed; this was attributed to different conducting mechanisms activated by temperature.