Optical properties of Cu-C70 nanocomposite under low energy ion irradiation

Abstract

Nanocomposite thin films consisting of Cu nanoparticles (NPs) embedded in fullerene C70 matrix are prepared by thermal co-deposition technique. Rutherford backscattering spectroscopy reveals that the thickness of thin film is about 35 nm and the atomic concentration on Cu metal is about 2%. The as-deposited thin films are irradiated with 120 keV N+ ions at various fluences ranging from 1 ×1014 ions cm−2 to 3 × 1016 ions cm−2. Low energy ion irradiation is proved to be an efficient technique to modify the optical, structural and electrical properties of nanocomposite thin films. Optical absorption spectra demonstrate that there was no signature of surface plasmon resonance (SPR) peak in the as-deposited film whereas a broad SPR band with the peak at ∼620 nm was observed for the film irradiated at the highest fluence (3 × 1016 ions cm−2). Raman spectroscopy is useful in providing information about the structural evolution of Cu-C70 nanocomposite thin films and confirms the gradual transformation of fullerene C70 into amorphous carbon with increasing fluence. Surface topography is probed by atomic force microscopy which shows the roughness of nanocomposite film varies with ion fluence.