Composition controlled LiCoO_2 epitaxial thin film growth by pulsed laser deposition

摘要

LiCoO_2 thin films were epitaxially grown by pulsed laser deposition (PLD). PLD is widely used to form complex oxide thin films due to the relatively small deviation in cationic composition between the target and the film. The deviation highly depends on the ablation laser conditions, and it greatly affects the quality of the epitaxial LiCoO_2 thin films. Furthermore, relatively lower oxygen pressure was found to result in higher quality LiCoO_2 thin films with suppressed impurity phases, although much higher oxygen pressure had been often used to avoid the formation of a lower valence state Co_3O_4 as an impurity. In other words, gas pressure also affects the composition in the case of lithium compounds, because lithium is even lighter than oxygen. The results clearly indicate that the difference in the composition between the target and the film is controllable by adjusting these parameters. In this study, we demonstrated the high-rate epitaxial growth of stoichiometric LiCoO_2 films by using a lithium-enriched target through composition control.