XPS insights: Asymmetric peak shapes in XPS

The misinterpretation of peak asymmetry as higher oxidation states in x‐ray photoelectron spectroscopy (XPS) is regretfully all too common. This XPS Insight note introduces the theory of peak asymmetry in x‐ray photoelectron spectra and such asymmetry is discussed for a range of different classes of materials to afford analysts a more informed view of their spectra.