Efficacy of ion irradiation in strengthening the surface plasmon resonance effect of Au nanoparticles

Abstract Au-Fullerene nanocomposite thin films synthesized by thermal co-evaporation method are irradiated by low energy (2.6 MeV) Ar ions at fluence ranging from 1 × 1014 ions-cm−2 to 3 × 1016 ions-cm−2. To avoid the retrogression of attributes of fullerene subjected to presence of Au, selected concentration and thickness of gold film is kept very small. UV–visible spectroscopy demonstrates the surface plasmon resonance (SPR) peak at 677 nm for the pristine film and at 590 nm after irradiation at fluence of 1 × 1014 ions-cm−2, displaying a shift of 87 nm towards lower side. This confirms that the refractive index of fullerene decreases as an influence of exposure to Ar beam irradiation. Shift in refractive index is explained on the basis of Mie theory which is established by the existence of D and G band after irradiation as displayed in the results of Raman Spectroscopy. A slight increase in the size of Au nanoparticles in irradiated films is observed which is illustrated by TEM images. Atomic Force Microscopy (AFM) images indicate the varying roughness of thin films after irradiation and morphology is determined by SEM images. I-V characterization shows the conductive behavior of Au-fullerene nanocomposite film before and after irradiation at different fluence. There are two phenomena occurring simultaneously with the increase in ion irradiation fluence; one is increase in the size of metal nanoparticle and another is transformation of fullerene in amorphous carbon. This leads to the change in the SPR position of metal fullerene nanocomposite thin film, making ion irradiation as an effective tool to enhance and optimize the optical properties of metal fullerene nanocomposite thin film.