Characteristics of the Li-Ni Doped Cobalt Oxide Thin Films Prepared by Pulsed Laser Deposition.

Cobalt oxide spinel thin films doped with Ni and Li were deposited on c-sapphire single crystal substrates at various substrate temperatures and oxygen partial pressures by pulsed laser deposition. The effects of the doping and processing parameters on the crystal structure, electrical and optical properties of cobalt oxide base spinel thin films were analyzed by XRD, four point probe and UV spectrometry. The electrical conductivity increased with increasing Ni doping concentration, x, up to x = 0.7. The thin films grew on the sapphire substrates with a strong (111) preferred orientation. Li0.1Ni0.6Co2.3O4 spinel phase decomposed to a rock salt phase when the oxygen partial pressure was lower than 5 mtorr. The electrical conductivity decreased rapidly with the formation of a rock salt phase due to the limited charge transfer between the divalent and trivalent cations.