Application of XANES and XPS in using synchrotron radiation in soft X-ray region for the study of the electronic structure of graphite and few-layered graphene fluorides
- Dr. Igor ASANOV
- Dr. Igor ASANOV (Nikolaev Institute of Inorganic Chemistry)
The compounds of fluorinated few-layered graphene are of great research interest as promising materials in nanoelectronics, optoelectronics, sensorics, and catalysis. The study of the electronic structure makes it possible to reveal the relationship between the structural features and the physicochemical properties of the compounds. X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) using synchrotron radiation in the soft X-ray range are among the most effective for studying the electronic structure of such nanomaterials. The work presents the results of combined synchrotron based XANES and XPS investigation of fluorinated graphene layers of different composition. Experimental CK, FK, NK XANES and XPS were obtained on the Russian-German beamline RGBL at synchrotron source BESSY II, and for dielectric samples the XPS results were supplemented by measurements on a laboratory spectrometer. The parameters of the electronic structure are studied when the composition of the fluorinated graphene layer varies from C2F to CF. Relationship between the local atomic and electronic structures are revealed depending on the size effect and composition. It is shown that with a decrease in the concentration of fluorine atoms, the energy gap decreases. Examples are given of the influence of the size effect on the composition and electronic structure of aminofluoride of graphite and few-layered graphene upon interaction of graphene fluorides with ammonia. It turns out that as a result of the interaction, fluorine atoms are removed from the surface (the reduction reaction) and the amine group is attached to the carbon layer. It can be noted that the concentration of fluorine in the aminofluorides increases with decreasing number of layers. It is presented the examples of the application of XANES and XPS in studying the mechanism of surface layer reduction in graphite fluorides of various compositions under the action of electron irradiation, changes of composition in depth, and changes in the electronic structure when the fluorine atoms are removed. The study of the interaction between the graphite fluoride matrix and various guest molecules in intercalation compounds of graphite fluoride such as bromine, ferrocene are presented. The results of this research are important for studying the mechanism of reduction of graphite fluorides and developing methods for the synthesis of graphene based compounds.
This work is financially supported by RFBR research project N 16-03-00048