X-ray photoelectron spectroscopy (XPS) is a technique for analyzing a material’s surface chemistry. XPS can measure elemental composition as well as the chemical and electronic state of the atoms within a material.

XPS spectra are obtained by irradiating a solid surface with a beam of X-rays and measuring the kinetic energy of electrons that are emitted from the top 1-10 nm of the material. A photoelectron spectrum is recorded by counting ejected electrons over a range of kinetic energies. The energies and intensities of the photoelectron peaks enable identification and quantification of all surface elements (except hydrogen).