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

Tantalum-Based Electrocatalyst for Polysulfide Catalysis and Retention for High-Performance Lithium-Sulfur Batteries

“…A slightly negative shift of radial distance is observed in a-Ta 2 O 5 /MCN (Figure S10), corresponding to the bond-length variation attributed to amorphous structure. 37 With the introduction of oxygen vacancies into Ta 2 O 5 , the oxygen-deficient environment weakens partial Ta-O coordination and reduces its radial distance, provoking severe structure distortion, 38 and thus there is only one scattering path corresponding to the dominant TaO6 octahedra present in a-Ta 2 O 5Àx /MCN (Figure 2F).…”

Relationship between Ta Oxidation State and Its Local Atomic Coordination Symmetry in a Wide Range of Oxygen Nonstoichiometry Extent of TaOx

“…This discrepancy indicates a strong dependency of the Ta-oxidation states on the experimental conditions of preparation of the nonstoichiometric oxide film. Nevertheless, the valence band (VB) photoelectron spectra show quite similar behavior with variation of the oxygen concentration, regardless of the differences in the TaO x production techniques. ,, The nonstoichiometry of tantalum oxide is accompanied by the formation of defect electron states about 2 eV above the VB maximum (VBM), which are ascribed to the presence of oxygen vacancies based on theoretical calculations. , …”

“…Denny et al also studied the local atomic structure of amorphous TaO x film deposited by the radio frequency sputtering method at different O 2 gas flow rates, which provides different x in TaO x (2.44–2.50) . In this paper, the Ta–O average bond length depending on different x values was analyzed by EXAFS spectroscopy.…”

“…Till date, the electronic and local atomic structure of Ta 2 O 5 and nonstoichiometric TaO x has been investigated in numerous works by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy methods. ,− The major part of these studies has focused on the effect of oxygen deficiency on the electronic properties of tantalum oxide. These works can be divided into two diametrically opposed groups according to the process of oxygen deficiency creation.…”

“…These works can be divided into two diametrically opposed groups according to the process of oxygen deficiency creation. The first group took advantage of reactive sputtering deposition of Ta films on a substrate, varying the rate of O 2 gas flow in the deposition chamber to produce TaO x with different extents of oxygen deficiency. ,, The second one exploited the effect of oxygen preferential sputtering by Ar + ions in Ta 2 O 5 to reduce the concentration of O. ,,,− Despite the difference in the approach to the nonstoichiometric TaO x preparation, Ta 4f photoelectron spectra of TaO x reported in previous studies show a common tendency: intermediate Ta-oxidation states appear with variation of oxygen concentration. However, there is a lot of controversy about the reported results on the Ta chemical states dynamics and the diversity of the Ta chemical states formed during the variation of oxygen concentration .…”