Raman and scanning tunneling spectroscopic investigations on graphene-silver nanocomposites

Graphene-silver (G-Ag) nanocomposites were prepared using liquid phase exfoliation of graphite flakes followed by a reduction of silver nitrate. The plasmonic characteristics of these nanocomposites are highly sensitive to the Ag concentration in the films. Raman spectroscopic investigations indicated that the effect of the surface-enhanced Raman scattering is present significantly in the Raman spectra of G-Ag nanocomposites. The intensity of the D, G, and 2D Raman bands is found to increase with silver concentration. The interaction between graphene and silver nanoparticles causes the G-band to split depending on the concentration of Ag. Scanning tunneling spectroscopic investigations showed that silver causes the Fermi level of graphene to shift towards the conduction band indicating the n-type doping and interestingly the existence of an offset current in the I-V characteristics of G-Ag nanocomposites differing from the zero value observed for graphene.