X-ray photoelectron spectrum of Fe2+ state in iron oxides

As a standard for identification of iron oxides by X-ray photoelectron spectroscopy, Fe²⁺ spectra are extracted from mixed Fe 2p_3/2 spectra of Fe³⁺, Fe³⁺ and metallic states. The peaks of Fe²⁺ spectra are all located at binding energy of 708·5 eV. The width of Fe²⁺ spectrum seems to be dependent on crystallinity, and is 2·2 eV for a bulk crystalline oxide and 2·9 eV for an amorphous thin film under instrumental condition with FWHM of 1·3 eV for Au 4f_7/2.