Electrochemical evaluation of oriented vanadium oxide films deposited by reactive rf magnetron sputtering

Abstract Thin films of crystalline V 2 O 5 were deposited by reactive rf magnetron sputtering from a metallic vanadium target in argon–oxygen gas mixtures at a substrate temperature of 300°C. We found that the orientation direction of V 2 O 5 films could be controlled by changing the oxygen flow ratio. Cyclicvoltammetry measurements for these films revealed that lithium diffused much faster in the a-axis oriented V 2 O 5 film than the b-axis oriented one. The surface morphology of these samples was also observed, however, there was not much difference between them, i.e.; lithium ion diffusion was not dominated by the porosity of the film in this case. We also found that chemical diffusion coefficient of Li along the a-axis of V 2 O 5 was larger than along the b-axis, hence, the lithium ion diffusion in V 2 O 5 film was attributed to the diffusing direction.