Effect of total gas and oxygen partial pressure during deposition on the properties of sputtered V2O5 thin films

Amorphous and crystalline vanadium pentoxide thin films have been deposited by rf magnetron sputtering in a pure argon or mixed argon/oxygen atmosphere using a V2O5 target with no intentional heating of the substrate. The effect of the total gas pressure and/or the oxygen partial pressure on the deposition rate, the composition, the structure, the surface morphology and the electrochemical properties of the films were investigated. The films were characterized by various methods such as X-ray Photoelectron Spectroscopy, Auger Electron Spectroscopy, XRD, Raman spectroscopy and SEM. The electrochemical performances have been evaluated by galvanostatic cycling. Thin films prepared in absence of oxygen or at a low oxygen partial pressure (10%) are amorphous and dense with a smooth surface, whatever the total pressure. In contrast, thin films prepared at an oxygen partial pressure higher than 10% are crystallized and mainly porous, the increase of the total pressure leading to a more pronounced preferential orientation with the c-axis perpendicular to the substrate. The best electrochemical results in terms of discharge capacity values are obtained for thin films prepared under a high total gas pressure. Moreover, dense thin films with a smooth surface are all showing a good cycling stability.