Computational Raman spectroscopy for organic adsorbates on graphene

How could we “see” the processes that occur in complex atomic-scale heterogeneous interfaces? It was suggested that Surface-enhanced Raman spectroscopy presents a keen approach for studying such systems, implying utilization of the Chemical Enhancement (CE). The latter is expected to report all information about the interfacial electronic coupling, however, a substantial learning curve is ahead before that information can be fully understood. The case of Graphene Enhanced Raman Spectroscopy (GERS) appears to be particularly intriguing. A delocalized electron system of graphene coupled with localized electronic states of organic adsorbates makes a significant challenge for understanding their Raman spectroscopy. We present a systematic computational study of Tetracyanoquinodimethane (TCNQ) adsorbed on graphene. This talk will report about simulations of surface-enhanced Raman spectra along with the supporting electronic structure analysis, focusing on the interfacial charge transfer and electron-phonon coupling. The application of a wide range of external electric biases allows us to modulate the charge transfer across the interface and reveal its role in corresponding changes of Raman spectra.