X-ray photoelectron spectroscopy study on the composition and structure of BaTiO3 thin films deposited on silicon

Abstract X-ray photoelectron spectroscopy (XPS) spectral analysis showed that Ba ions in BaTiO3 thin films prepared by the sol–gel technique consist of one phase corresponding to one electronic state, which we call the β-phase. This phase became stronger at the same depth with increasing annealing temperature. With our preparation conditions, we can prepare BaTiO3 thin films with Ba electronic states as in bulk BaTiO3. During Ar+ sputtering, a mixture of the different oxidation states Ti+2, Ti+3, Ti+4 of titanium are present as established by XPS. The concentration of Ti+3 increases with increasing annealing temperature. For thin films annealed at 675°C the atomic concentration of Ti+3 is of the order of that of Ti+4. The binding energy of the oxygen O 1s main peak increases with increasing number of sputter cycles. Oxygen atoms terminating the oxide surface are bound differently from subsurface oxygen atoms. Outer-layer oxygen atoms are less negatively charged than in the normal oxide state. X-ray diffraction patterns and XPS analysis of the annealed films show that films annealed at 600°C for 2 h have high crystallinity, the desired stoichiometry, and less Ti+3 defects.

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