Investigation on tip enhanced Raman spectra of graphene

(a), (b), (c) SEM images of the nanowire, and the images(Ia, IIa, IIIa) that the incident laser coupled with TERS tip when the TERS tip got attached to different areas of Ag-nanowire. (d) TERS spectra correspond to the position (Ia, IIa, IIIa), and the spectra Ib, IIb and IIIb and were measured with the tip attached to the sample, and Ic, IIc and IIIc were measured with the tip retracted. Obviously, the intensity of D-bond and D'-bond was the weakest when the TERS tip got attached to the endpoint (I) of the Ag-nanowire, however the particularly high signal enhancement emerges from the position III. Such Raman enhancement is attributed to the effect of excitation of LSP by the nanoparticle at position III. The nanoparticle acts as an antenna that enhances the both incident and the emitted fields. Furthermore, the distribution features of surface plasmons on Ag-nanowires were revealed.316