Ion irradiation-induced effects on optical and structural properties of Ge nanoparticles synthesized by laser ablation

Abstract

We present here the effects of swift heavy ion irradiation on the optical and structural properties of Germanium (Ge) nanoparticles (NPs) synthesized by using laser ablation of bulk Ge wafer in liquids. The Ge NPs have been irradiated with 120 MeV Ag ions of various fluences ranging from 5 × 1012 to 1 × 1014 ions/cm2. The effect of ion irradiation on optical and structural properties of the Ge NPs has been studied with transmission electron microscopy (TEM), Raman scattering, and photoluminescence (PL) emission measurements. We have observed a decrease in the average size of the Ge NPs upon increasing the fluence of irradiation, amorphization at high fluence, and smaller NPs started to grow in the vicinity of larger sized NPs under ion irradiation. Therefore, the proper selection of fluence can be tuned to modify the existing NPs and synthesize new NPs. The NPs became amorphous at the higher fluence with the core remaining crystalline while the shell transformed into an amorphous phase. From Raman scattering results, the shift observed in peak position and the increase in the broadening in the Ge phonon vibrational peak indicates a reduction in NPs size. The PL emission is also blue-shifted upon increasing the irradiation fluence.