Investigation of Li/Nb-sublattices in ion implanted LiNb03 by RBS and NRA in channelling configuration

摘要

Differently oriented LiNbO_3 crystals were implanted at room temperature with 1 MeV iodine ions to flu-ences between 2 x 10~(13) and 1 x 10~(14)cm~(-2), which cover the transition from a low damage level up to complete amorphisation. The aim of this work was to explore the use of nuclear reaction analysis (NRA) in combination with Rutherford backscattering spectrometry (RBS) in channelling configuration for studying the damage evolution as a function of the ion fluence in both the Li and Nb sublattice. Protons with energies between 1.4 and 1.6 MeV and a standard RBS setup were used. Scattering events detected at low energies result from Rutherford backscattering of protons on Nb and 0 atoms. At high energies alpha particles are registered, which result from the nuclear reaction between protons and Li atoms. Along different low-index crystallographic directions channelling effects within both the RBS and NRA part of the spectra are observed. However, the strength of channeling within the NRA part depends on the crystallographic direction investigated. These effects are explained by the nature of ion-channelling with respect to the small atomic number of Li and is supported by calculations of minimum yields (ratio of scattering yield in aligned and random direction) applying the computer code DICADA. The consequence is that damage studies with NRA can be only performed in Z-direction of LiNbO_3. In this case, the Li and Nb sublattice were found to be similarly damaged after 1 MeV iodine implantation.