An analytical method that determines the elements in the top few nanometers of a surface and their chemical bonding state (oxidation state and so on) from the binding energies of photoelectrons emitted by X-rays.
Japanese name: XPS(X線光電子分光法)
XPS (X-ray photoelectron spectroscopy) appears in 2 practice questions across 1 topic, including Materials characterization (SEM, TEM, XRD, XPS).
Answer: B. The information depth is a few nanometers, and chemical shifts of the peaks reveal the bonding state of elements (oxidation state and so on)
In XPS the incident X-rays themselves penetrate several micrometers into the specimen, but the photoelectrons produced readily lose energy by inelastic scattering, and only those generated within a few nanometers of the surface escape with their original energy. XPS is therefore a technique that probes the topmost few nanometers. The binding energy of photoelectrons shifts slightly with the chemical state of the atom (chemical shift); for Si 2p, for example, SiO₂ is about 4 eV higher than elemental Si, so the presence of oxidation and the oxidation state can be distinguished. Depth distributions are investigated by measuring while sputtering with Ar ions or by varying the photoelectron take-off angle. Determining the average composition to a depth of several micrometers is the job of techniques such as EDS in the SEM.
Answer: C. About 103.3 eV
From energy conservation in the photoelectric effect, the binding energy is E_B = hν − E_K − φ = 1486.6 − 1378.8 − 4.5 = 103.3 eV. The Si 2p binding energy of elemental Si is about 99 eV, so this value, about 4 eV higher, is typical of SiO₂ (Si⁴⁺), indicating that the surface is oxidized. About 107.8 eV forgets to subtract the work function, and about 112.3 eV adds it where it should be subtracted. When measuring insulators, charging shifts the peaks, so binding energies are often corrected by referencing the C 1s peak of adventitious carbon on the surface (about 284.8 eV).
In XPS the incident X-rays themselves penetrate several micrometers into the specimen, but the photoelectrons produced readily lose energy by inelastic scattering, and only those generated within a few nanometers of the surface escape with their original energy.
Which correctly describes the information depth of XPS (X-r…EDS (energy-dispersive X-ray spectroscopy) SEM (scanning electron microscope) Bragg's law Extinction rules Scherrer equation SIMS (secondary ion mass spectrometry) XRD (X-ray diffraction)