Title
X-Ray absorption, photoemission spectroscopy, and Raman scattering analysis of amorphous tantalum oxide with a large extent of oxygen nonstoichiometry
Author
Takashi Tsuchiya, Hideto Imai, Shogo Miyoshi, Per-Anders Glans, Jinghua Guo and Shu Yamaguchi
Year
2011
Journal
Physical Chemistry Chemical Physics
Abstract
The electronic structure and modification of the local interatomic structure of a reactive sputtered amorphous tantalum oxide (a-TaOx) thin film with the variation of oxygen nonstoichiometry, x in a-TaOx have been investigated by X-ray absorption spectroscopy (XAS), X-ray photoemission spectroscopy (XPS), Raman scattering spectroscopy, and Rutherford back scattering spectroscopy. A parallel chemical shift of Ta4f7/2 and O1s core levels observed with the variation of x indicates the Fermi level shift by reduction and oxidation in the framework of the rigid band model. Extended X-ray absorption fine structure (EXAFS) suggests both the increase of average coordination number of the first Ta?O shell in polyhedra and a considerable reduction of the average Ta?O bond length with the increase of x. The relative intensity of Raman shift peaks at 670 cm?1 and 815 cm?1, corresponding to Ta?O stretching of TaO6 octahedra and TaO5 probably with a pyramidal form, respectively, drastically changes between x = 2.47 to 1.86, suggesting the change in the predominant polyhedron from TaO6 to TaO5 with a modification in multiplicity of oxygen by the reorganization of the polyhedral network.
Instrument
NRS-5100
Keywords
Raman Imaging Microscopy, Electrodes, Salts, Ionic Liquids, Lithium, Solvation