Study of thin films of mixed uranium oxides/nitrides by Photoemission and AES. Films have been prepared by reactive sputter deposition in an Ar plasma in presence of N2 and O2 admixtures. Aim: elucidate if a solid solution of UO and UN (known as uranium oxynitride UNxO1-x) can form by this synthesis method. Such ternary oxide has been described for bulk compounds. Since sputter deposition can produce very finely dispersed systems, this looked like a good method for producing the oxynitride. Oxynitride has uranium in a low oxidation state (UN: formally 3; UO: formally 2). Initially UN films with an increasing oxygen content were deposited. ). The oxynitride is metallic and it can be ashat the U5f are still itinerant and pinned the EF: for UN they are and for UO they also should be. We studied whether the oxygen incorporation goes along with a DOS at EF (pointing to UO formation) or whether it simply leads to the formation of the UO2 semiconductor (no DOS at EF)- Experiment: The series started with deposition of UN and then increasing gradually the O2 pressure. U4f, O1s and VB spectra (by HeII). Also Auger spectra of U, O and N were taken. Depositions were done at room temperature and elevated temperature. We searched for the onset of UO2 formation (characteristic U4f peak), because at sufficiently high O2 pressure this oxide will form – oxygen simply displaces nitrogen. File Format: Files are stored in the VAMAS format. This is a universal formed used by commercial data analysis programs such as CasaXPS. Description of the VAMAS format can by found in the internet