Effect of oxygen deficiency on electronic properties and local structure of amorphous tantalum oxide thin films

• The effect of oxygen flow rate on electronic properties and local structure of tantalum oxide thin films was studied.
• The oxygen deficiency induced the nonstoichiometric state a-TaOx.
• A small peak at 1.97 eV above the valence band side appeared on nonstoichiometric Ta2O5 thin films.
• The oxygen flow rate can change the local electronic structure of tantalum oxide thin films.

The dependence of electronic properties and local structure of tantalum oxide thin film on oxygen deficiency have been investigated by means of X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results showed that the oxygen flow rate change results in the appearance of features in the Ta 4f at the binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV whose peaks are attributed to Ta1+, Ta2+, Ta3+/Ta4+, and Ta5+, respectively. The presence of nonstoichiometric state from tantalum oxide (TaOx) thin films could be generated by the oxygen vacancies. In addition, XAS spectra manifested both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the decrease of oxygen deficiency.

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