Electrical properties of Li-doped NiO films

Lithium-doped NiO films were deposited by radio frequency magnetron sputtering on Corning 1737 glass substrates. The Li concentrations in the films varied from 0 to 16.29 at.%, as determined by wavelength-dispersive X-ray analysis and inductively coupled plasma mass spectrometry. The effects of Li content on properties such as microstructure, resistivity, and electrical stability were studied. The results show that the doped Li ions tend to occupy crystal defect sites such as vacancies or segregate on the film surface. Initially, doped Li occupied the nickel vacancies in the film, decreasing the electrical conductivity. When the Li concentration was further increased, some Li segregated on the film surface and formed bulges at high Li concentrations. These Li-rich oxides covering the film surface served as partitions between the film and moisture from the atmosphere. As a result, the Li-doped NiO films show a relatively high arrestment to electrical resistance aging.