X-ray photoelectron spectroscopy
Principle
X-ray photoelectron spectroscopy (XPS) is a surface sensitive analysis technique (~5-10 nm) whose principle is based on the detection and analysis of core electrons ejected from samples when irradiated with an X-ray beam (photoelectric effect). The kinetic energy of the emitted electrons, called photoelectrons, is characteristic of the electronic layers of the excited atoms, allowing for the identification of all elements (except H and He). Moreover, the energy of the emitted core photoelectrons is also influenced by the chemical environment of the atoms (oxidation sate and bonding). Through this spectroscopic method, semi-quantitative information regarding the elemental composition and the chemical environment of atoms in solid samples can thus be obtained. UV photoelectron spectroscopy (UPS) uses a UV photons source whose lower energy (compared to X-ray photons) allows to probe the valence band structure of the analysed sample.
For whom?
The analyses supplied by the SMI platform are aimed at a wide audience: engineers and technicians from the public and private sectors, researchers, lecturers, PhD, postdoctoral students, etc.
For what ?
The XPS technique provides qualitative and quantitative information on the surface chemical composition (~5-10 nm) and the chemical environment of atoms (nature of bonds, oxidation state of atoms). All atoms can be detected (except hydrogen and helium). In order to intensify the response of the extreme surface in the study of thin films, it is possible to vary the detection angle of the photoelectrons (ARXPS). An Argon ion gun is also used to etch the surface to remove the first atomic layers and obtain a deep analysis profile. UPS spectroscopy allows to characterize the valence band of a sample.
How ?
XPS and UPS spectroscopies are non-destructive analysis techniques, adapted to any type of solid sample (conductive or insulating) compatible with ultra-high vacuum. The sample can be a powder, a thin film, or a wafer. The materials studied are very diverse in nature: nanomaterials, mineral phases, organo-mineral hybrids, polymers, biological materials (biofilms, antimicrobial materials), sensors, dehydrated food materials… and thus cover a wide disciplinary field.