1. Introduction X-ray Photoelectron Spectroscopy (XPS) is a surface-sensitive quantitative spectroscopic technique that measures the elemental composition, chemical state, and electronic state of the elements within a material. It is one of the most widely used surface analysis methods due to its ability to probe the top 1–10 nm of a sample. 2. Fundamental Principle XPS operates on the photoelectric effect . A sample is irradiated with monochromatic X-rays (typically Al Kα or Mg Kα). When an X-ray photon (energy ( h\nu )) strikes an atom, it can transfer its energy to a core-level electron. If the photon energy exceeds the electron's binding energy (( E_b )), the electron is ejected from the atom as a photoelectron .
The kinetic energy (( E_k )) of the ejected photoelectron is measured by an electron analyzer. The binding energy is then calculated using: When an X-ray photon (energy ( h\nu ))
[ E_b = h\nu - E_k - \phi ]