Investigation of sequential thermal annealing effect on Cu-C70 nanocomposite thin film

Cu-C70 nanocomposite thin film is synthesized via thermal co-evaporation method. The atomic concentration of Cu in the thin film is found to be ~4.5 at.% using Rutherford backscattering spectroscopy. Sequential thermal annealing is performed in an inert atmosphere (in presence of Ar) at various temperatures. Surface plasmon resonance (SPR) is spotted at ~585 nm for the sample annealed at 300 °C and the SPR peak is shifted towards ~621 nm for the sample annealed at 400 °C. In order to determine the modifications arising in the structure of fullerene C70 matrix due to annealing, Raman spectroscopy is used. At the highest temperature of 400 °C, the high-intensity Raman active modes of fullerene C70 can still be observed which shows that fullerene C70 is not completely transformed into amorphous carbon upto this temperature. Transmission electron microscopy is performed to determine the size of particles which is obtained ~35 nm for the sample annealed at 400 °C. The red shift in SPR wavelength at 400 °C is ascribed to the growth of Cu nanoparticles.