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- Takahashi, M., et al.
(författare)
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Oxygen annealing effect of photoelectron spectra in SrBi2Ta2O9 film
- 2002
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Ingår i: Japanese Journal of Applied Physics. - 0021-4922 .- 1347-4065. ; 41:11B, s. 6797-6802
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Tidskriftsartikel (refereegranskat)abstract
- Photoelectron spectra have been studied to clarify O-2-annealing effects on the band diagram of the metal-SrBi2Ta2O9 (SBT) junction and ionization energy of SBT films deposited by the pulsed laser, deposition (PLD) method. Photoemission spectra obtained by ultraviolet light irradiation have a threshold of 5.90 eV for the as-deposited SBT film and 5.56 eV for the O-2-annealed one. This shift of the threshold indicates that the annealing treatment has increased the Fermi level by 0.34 eV. On the assumption of a 4.2 eV band gap and 3.5 eV electron affinity for the SBT, as-deposited SBT has been estimated to give a 0.60 eV lower barrier height for holes than that for electrons, which is possibly because of, insufficiently oxidized (Bi2O2)(2+) layers as indicated by X-ray photoelectron spectroscopy (XPS). After annealing in O-2, however, barrier height energies for holes and electrons become closer to each other. These results agree with our previous studies which have reported that the O-2-annealing suppressed the leakage current through SBT and improved the retention characteristics of the metal-ferroelectric-insulator-semiconductor structure.
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