X-ray Photoelectron Spectroscopy (XPS) is the most used technique for the investigation of the chemical properties of the material. In this technique a monochromatic radiation impinges on the sample and extracts photoelectrons. These photoelectrons are then collected and their energy dispersion is recorded by an electron energy analyzer. This forms the so called electron dispersion curve (EDC) or photoemission spectrum. From the analysis of the photoemission spectrum it is possible to derive the chemical composition (stoichiometry) of the material under study and several information about the chemical state of each element, such as oxidation state, chemical bonds, etc.
MBE cluster system includes one chamber devoted to XPS analysis. The chamber is equipped with one close cycle cryostat that allows the control of the sample temperature in a range between 25 and 300 K. The chamber is equipped with a double anode (Mg,Al) x-ray source and with a electrostatic hemispherical analyzer (mean radius 200 mm). The X-ray source is non-monochromatized and forms with the photoelectron propagation direction an angle of 90 degrees. The manipulator allows the rotation of the polar angle, in order to change from the (almost) normal emission condition to grazing emission (and therefore from grazing incidence of the x-rays to normal incidence). The figure displays the experimental system, which is also equipped with a sputtering device.