Growth of V₂O₅ Films for Electrochromic and Battery Applications by Pulsed Chemical Vapour Deposition

Pulse chemical vapour deposition (CVD), or more correctly atomic layer deposition (ALD) outside of the ALD thermal window, was used to grow vanadium pentoxide films using Tetrakis(dimethylamino)vanadium (IV) (V(NMe2)4) as the vanadium source and either oxygen-argon plasma, oxygen or water as the co-reagent. Growths were performed at 150-300°C for 400 cycles, resulting in a range of both stoichiometric and non-stoichiometric vanadium oxides. Post growth annealing in air at 400°C for both thermal and plasma assisted methods resulted in the formation of orthorhombic α – V2O5. Electrochemical characterization revealed that the samples grown at 250°C using a plasma process and a post growth anneal demonstrate the best electrochemical properties in terms of current density and charge density with values of 0.35 mAcm-2and 55 mCcm-2 respectively. In addition, the samples grown under these conditions also possess the best electrochromic response, exhibiting a change in percentage transmission between the bleached and coloured states of 65%. The influence of growth parameters on material properties is discussed.