Thickness-Dependent Morphologies and Surface-Enhanced Raman Scattering of Ag Deposited on n-Layer Graphenes

摘要

After thermal deposition of silver films onto n-layer graphenes, the following results have been obtained. First, the dependence of silver morphologies on the layer number is studied via controlling the sample temperature at 298, 333, and 373 K. This can be attributed to the changes in surface properties and/or surface diffusion coefficient of n-layer graphenes at different temperatures. Second, Raman scattering of n-layer graphenes is greatly enhanced after Ag deposition and the enhancement factors depend on the layer number of n-layer graphenes. Monolayer graphene has the largest enhancement factors, and the enhancement factors decrease with layer number increasing. For graphite, almost no enhancement effect has been detected. Third, the dependences of the enhancementfactors on laser wavelength, thickness, and morphologies (nanoparticle size and spacing) of silver film are also studied. The Raman enhancement observed here is mainly attributed to the coupled surface plasmon resonance (SPR) absorption of silver nanoparticles.