Atomic displacement and disorder in LiNbO3 single crystal caused by high-energy 3He ion irradiation: an x-ray absorption spectroscopy study

Nb K-edge x-ray absorption fine structure spectra from a single lithium niobate (LN) crystal irradiated with high-energy 3He ions of 41 MeV and from unexposed crystal as the reference material are compared. The differences in the x-ray absorption near edge structure (XANES) spectra are interpreted by simulating Nb K-edge XANES spectra with the FEFF8.2 code. It is found that displacements of Nb and Li atoms, as well as Li and O vacancies, are likely to cause structural disorder leading to change in the refractive index of LN and to diminished birefringence. This finding is in agreement with previous results obtained from SRIM-2003 simulations and transmission electron microscopy measurements.