X-ray photoelectron spectroscopy study on the composition and structure of BaTiO 3 thin films deposited on silicon

Abstract

X-ray photoelectron spectroscopy (XPS) spectral analysis showed that Ba ions in BaTiO 3 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 BaTiO 3 thin films with Ba electronic states as in bulk BaTiO 3. 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.