Thermal annealing and SHI irradiation induced modifications in sandwiched structured Carbon-gold-Carbon (a-C/Au/a-C) nanocomposite thin film

Abstract

In the present work, we study the annealing and swift heavy ion (SHI) beam induced modifications in the optical and structural properties of sandwiched structured Carbon-gold-Carbon (a-C/Au/a-C) nanocomposite (NCs) thin films. The NCs thin films were synthesized by electron-beam evaporation technique at room temperature with ∼30nm thickness for both carbon layer and ∼6nm for gold layer. Gold-carbon NCs thin films were annealed in the presence of argon at a temperature of 500°C, 600°C and 750°C. The NCs thin films were also irradiated with 90MeV Ni ions beam with different ion fluences in the range from 3×1012, 6×1012 and 1×1013ions/cm2. Surface plasmon resonance (SPR) of Au nanoparticles are not observed in the pristine film but, after annealing at temperature of 600°C and 750°C, it was clearly seen at ∼534nm as confirmed by UV–visible absorption spectroscopy. 90MeV Ni irradiated thin film at the fluence of 1×1013ions/cm2 also show strong absorption band at ∼534nm. The growth and size of Au nanoparticle for pristine and 90MeV Ni ion irradiated thin film with fluence of 1×1013ions/cm2, were estimated by Transmission electron microscopy (TEM) images with the bi-model distribution. The size of the gold nanoparticle (NPs) was found to be ∼4.5nm for the pristine film and ∼5.4nm for the irradiated film at a fluence of 1×1013ions/cm2. The thickness and metal atomic fraction in carbon matrix were estimated by Rutherford backscattering spectroscopy (RBS). The effect of annealing as well as heavy ion irradiation on D and G band of carbon matrix were studied by Raman spectroscopy.