Valence state map of iron oxide thin film obtained from electron spectroscopy imaging series

Ko Feng Chen, Shen Chuan Lo, Li Chang, Ray Egerton, Ji Jung Kai, Juhn-Jong Lin, Fu Rong Chen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


This paper demonstrates the applicability of electron-spectroscopic imaging (ESI) for valence-state mapping of the iron oxide system. We have previously developed a set of signal-processing methods for an ESI series, to allow mapping of sp2/sp3 ratio, dielectric function and energy bandgap. In this study, these methods are applied to generate a valence-state map of an iron oxide thin film (Fe/α-Fe2O3). Two problems, data undersampling and a convolution effect associated with extraction of the image-spectrum from the core loss image series, were overcome by using cubic-polynomial interpolation and maximum-entropy deconvolution. As a result, the reconstructed image-spectrum obtained from the ESI series images has a quality as good as that of conventional electron energy-loss spectra. The L3/L2 ratio of the reconstructed ESI spectrum is determined to be 3.30 ± 0.30 and 5.0 ± 0.30 for Fe and α-Fe2O3, respectively. Our L3/L2 ratio mapping shows an accurate correspondence across the Cu/Fe/α-Fe2O3 region. The effect of delocalization and chromatic aberration on the ESI resolution is discussed and estimated to be about 2 nm for the case of L3/L2 ratio mapping.

Original languageEnglish
Pages (from-to)354-361
Number of pages8
Issue number4
StatePublished - 1 Jun 2007


  • Electron energy-loss spectroscopy(EELS)
  • Electron spectroscopic imaging(ESI)
  • Iron oxide system
  • Valence state map

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