XPS analysis on chemical states of Li4SiO4 irradiated by 3 keV D2+

Li4SiO4 will be applied as tritium breeding materials in future fusion reactor. The release behavior of tritium from neutron-irradiated Li4SiO4 should be sensitive to the chemical states of lithium, oxygen and silicon on the surface of Li4SiO4 with irradiated defects. The present study is focused on the influence of hydrogen isotopes and irradiation defects on surface chemical state of Li4SiO4. The X-ray Photoelectron Spectroscopy (XPS) was compared between non-irradiated Li4SiO4 and D2+-irradiated one. It was observed by that the binding energy (BE) of electron for Li-1s, O-1s and Si-2p of non-irradiated Li4SiO4 were 60.9 eV, 536.1 eV and 107.1 eV respectively. However new XPS peak for Li-1s at 57.2 eV, three XPS peaks for O-1s (at 536.1 eV, 533.2 eV and 531.3 eV, respectively) and three XPS peaks for Si-2p (at 107.1 eV, 104.2 eV and 99.7 eV, respectively) were observed in D2+-irradiated Li4SiO4. It is considered that the XPS peaks of 531.3 eV and 104.2 eV should be corresponding to O-1s and Si-2p in –Si–O–D while the XPS peak of 533.2 eV should be corresponding to O-1s in D–O–D. The formation of –Si–O–D and D–O–D is considered to be due to typical irradiated defects (lithium vacancy, silicon vacancy and implanted deuterium) induced by D2+-irradiation.