The XPS system enables quantitative element analysis at surfaces of solid materials by spectroscopy of emitted photo electrons, and gives information on the chemical states by analysis of peak-shifts or peak-shape changes.
The operating principle of XPS is the photoelectric effect: emission of an electron from an element due to collision between a photon ad an atomic electron. For this to occur the photon energy must exceeds a critical value, the ejected electron escapes with a kinetic energy equal to the difference between the incident energy of the photon and the energy required to remove the electron from its orbital into space (its original binding energy minus the work function). Knowing the phton energy and the kinetic energy of the emitted electron allows to calculate the binding energy, which can be used to identify the emitting atom.
The XPS 5600 operates by striking the sample with a high energy photon (an X-ray from a Mg or Al based source) and measuring the kinetic energy of all of the ejected electrons. The binding energies of these electrons are then calculated and from these a distribution of atomic species is determined. The lightest element that XPS can detect is lithium. Even though the X-ray photons can penetrate deeply into the material, scattering limits only electrons from the top 5-10 nm to be ejected without attenuation of their kinetic energy. Thus, XPS is considered a surface sensitive technique.
In addition to determining the atomic composition of the surface, XPS can also provide semi-quantitative information (expressed in units of atomic percent) by dividing the peak areas of each element by sensitivity factor, which is simply the probability of a particular element to emit an electron when struck by a photon. The sensitivity of XPS is element-dependent, with larger elements (which have larger sensitivity factors) being more sensitive than smaller elements.
Samples must be solid and ultra high vacuum compatible (should not have a low sublimation pressure or be excessively oily, etc.).
Maximum sample dimensions are roughly 2 cm in diameter and 1 cm in height.Wafer materials
Contact: Dr. Jorge A. Lopez, email@example.com.