title: Valence state map of iron oxide thin film obtained from electron spectroscopy imaging series.
abstract: 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 sp(2)/sp(3) 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/alpha-Fe(2)O(3)). 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 L(3)/L(2) ratio of the reconstructed ESI spectrum is determined to be 3.30+/-0.30 and 5.0+/-0.30 for Fe and alpha-Fe(2)O(3), respectively. Our L(3)/L(2) ratio mapping shows an accurate correspondence across the Cu/Fe/alpha-Fe(2)O(3) 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 L(3)/L(2) ratio mapping.
authors.affiliation: Department of Engineering and System Science, National Tsing Hua University, HsinChu 30013, Taiwan.
authors.forename: Ko-Feng
authors.initials: KF
authors.lastname: Chen
authors.forename: Shen-Chuan
authors.initials: SC
authors.lastname: Lo
authors.forename: Li
authors.initials: L
authors.lastname: Chang
authors.forename: Ray
authors.initials: R
authors.lastname: Egerton
authors.forename: Ji-Jung
authors.initials: JJ
authors.lastname: Kai
authors.forename: Juhn-Jong
authors.initials: JJ
authors.lastname: Lin
authors.forename: Fu-Rong
authors.initials: FR
authors.lastname: Chen