Radiation damage by light- and heavy-ion bombardment of single-crystal LiNbO_3

Abstract

In this work, a battery of analytical methods including in-situ RBS/C, confocal micro-Raman, TEM/STEM, EDS, AFM, and optical microscopy were used to provide a comparative investigation of light- and heavy-ion radiation damage in single-crystal LiNbO<sub>3</sub>. High (~MeV) and low (~100s keV) ion energies, corresponding to different stopping power mechanisms, were used and their associated damage events were observed. In addition, sequential irradiation of both ion species was also performed and their cumulative depth-dependent damage was found. It was found that the contribution of electronic stopping from high-energy heavy ions gave rise to a lower critical dose for damage formation than the use of low-energy irradiation. Such energy-dependent critical dose of heavy-ion irradiation is two to three orders of magnitude smaller than that for the case of light-ion damage. In addition, materials amorphization and collision cascades were seen for heavy-ion irradiation, while for light ion, crystallinity remained for the highest dose used in the experiment. The irradiation-induced damage is characterized by the formation of defect clusters, elastic strain, surface deformation, as well as change in elemental composition. The presence of nanometric-scale damage tracks results in increased RBS/C backscattered signal and the appearance of normally forbidden Raman phonon modes. The location of the highest density of damage is in good agreement with TRIM calculations.