Tandem analytical techniques, such as scanning tunneling microscopy (STM) tip-enhanced Raman spectroscopy (TERS), offer the capability to combine spatial resolution with chemical information. These methods allow the interrogation of surface interactions with angstrom-scale resolution. Intermolecular and molecule-substrate interactions determine the self-assembly of organic molecules on a surface, and highly localized chemical effects can have profound consequences on the formation of nanoarchitectures. As a result, new techniques must be applied to these systems in order to more fully interrogate and understand the effects of these interactions. Through the combination of Ultrahigh Vacuum (UHV) STM-TERS with density functional theory (DFT) calculations we have studied and characterized the interactions of self-assembled organic molecules on metal surfaces. Porphyrin and phthalocyanine derivatives relevant to organic and printed electronics as well as photovoltaics were selected in this study, as their surface interactions are fundamental to the nature of their implementations in devices. STM-TERS and DFT calculations were used to reveal molecular fingerprints and intramolecular bond information spectroscopically with sub-nanoscale spatial resolution. Through this method the location of specific vibrational modes can be defined, and subtle differences visualized. Subsequently, this intramolecular resolution has been applied to investigate the highly localized effects of molecule-substrate and molecule-molecule interactions based on shifts in the energies and intensities of specific vibrational modes.

Intramolecular insights into adsorbate-substrate interactions by tip-enhanced Raman spectroscopy at the angstrom-scale

2019 Fall National Meeting

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