X-RAYS FOR ANALYSIS OF SURFACES AND INTER FACES

Because of their low cross section of interaction with atoms, X rays a re not used as much for surface analysis than for bulk studies. Howerv er they give useful informations through several commonly used methods . If one plays with the various interactions between X rays and matter , one can test the first nanometers of the materials either working at very grazing incidence, or analyzing electrons emitted by the materia l under invetigation which have a very small mean free path, or studyi ng fluorescence issued from the topmost layers. Photoemission (XPS or ESCA) is one of the most powerful methods to analyze the chemical comp osition of surfaces. It can also give surface structure informations ( XPD). Analysis of extended X-ray absorption fine structures (EXAFS and SEXAFS) is a good method for local order evaluation and it works for surface and buried interfaces. Synchrotron radiation is more and more widely used since it is a source of polarized light (either linearly o r circularly) and after having being used extensively for XPD and EXAF S can be devoted to new spectroscopies sensitive for example to surfac e magnetism (magnetic dichroism in photoemission).