Annealing effects on the optical and electrochemical properties of tantalum pentoxide films

Tantalum pentoxide (Ta2O5) has attracted intensive attention due to their excellent physicochemical properties. Ta2O5 films were synthesized via electron beam evaporation (EBE) and subsequently annealed at different temperatures ranging from 300 to 900 °C. X-ray diffraction (XRD) results show that amorphous Ta2O5 thin films form from 300 to 700 °C and then a phase transition to polycrystalline β-Ta2O5 films occurs since 900 °C. The surface morphology of the Ta2O5 films is uniform and smooth. The resulted Ta2O5 films exhibit excellent transmittance properties for wavelengths ranging from 300 to 1100 nm. The bandgap of the Ta2O5 films is broadened from 4.32 to 4.46 eV by annealing. The 900 °C polycrystalline film electrode has improved electrochemical stability, compared to the other amorphous counterparts.