Principal Component Analysis (PCA) unravels spectral components present in XPS spectra of complex oxide films on iron foil

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Principal component analysis (PCA), as applied to the processing of the complex X-ray photoelectron spectroscopy (XPS) lineshapes, is discussed. PCA analysis example is provided of complex native iron oxide films on Fe foil XPS spectra further modified by argon and helium ion beams. Abstract PCA components are derived from Fe 2p, O 1 s and C 1 s regions leading to the assignments of surface (oxy)hydroxide, Fe2O3, FeO and Fe metal, as corroborated by the corresponding elemental quantification profiles. Detailed mathematical concepts behind PCA analysis of spectra data are provided.