Stability of nanoparticles in LiNbO 3 induced by negative Cu ions and ultrafast nonlinear optical property

Abstract

Kinetic behaviors of nanoparticle formation in LiNbO 3 have been studied with negative Cu ion implantation and the effects on nonlinear optical properties have been discussed. Negative Cu ions of 60 keV are implanted into LiNbO 3 disks at fluxes up to 50 μA/cm 2. Ion-induced photon spectroscopy was applied to monitor the ion-substrate interactions and the nanoparticle morphology was studied by cross-sectional TEM. Metal precipitation behaviors as well as the matrix stability significantly depended on ion flux. In a flux range of 3–10 μA/cm 2, LiNbO 3 showed spontaneous formation of Cu nanocrystals of ∼10 nm, including nonspherical shape. Crystallinity of the LiNbO 3 lattice implanted was sustained up to 3 × 10 16 ions/cm 2. The Cu nanoparticles in LiNbO 3 showed a sub-picosec nonlinear optical response. However, significant Li-atom release to the vacuum was detected by ion-induced photon spectroscopy, indicating formation of a Li-depleted zone. Particularly above a flux of 30 μA/cm 2, significant coarsening of Cu particles and amorphization of the LiNbO 3 lattice occurred. The results indicate that metal nanoparticle formation in LiNbO 3 is sensitive to the ion flux and that the optimization is requisite to fabricate well-defined nanocomposites.