| AVS 60th International Symposium and Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS+AS+NS+SP-WeA |
| Session: | Single Molecules at Surfaces: Structure and Dynamics |
| Presenter: | N. Jiang, Northwestern University |
| Authors: | N. Jiang, Northwestern University J. Klingsporn, Northwestern University E. Pozzi, Northwestern University M.C. Hersam, Northwestern University R.P. Van Duyne, Northwestern University |
| Correspondent: | Click to Email |
The study of ultrahigh vacuum (UHV) tip-enhanced Raman spectroscopy (TERS) has been raised to an unprecedented level. By using ex-situ laser focusing and Raman collection optics, optimization of the optical path is achieved without compromising UHV. All sample preparation and tip degassing are performed in-situ, maintaining atomically clean surfaces, greatly enhancing the stability of the tip-sample junction, and ensuring minimal contamination in the field enhancement region beneath the STM tip. At 292K, multiple vibrational modes for copper phthalocyanine (CuPc) adlayers on Ag (111) have been resolved in TER spectra obtained concurrently with molecular resolution UHV Scanning tunneling Microscopy (STM). Then Rhodamine 6G (R6G) molecules were studied as they have larger Raman cross-section. The sample was cooled down to 19 K to decrease the diffusion of R6G on surface at very low coverage. Single R6G molecules and clusters were observed using STM. For the first time, TERS vibrational modes for a few R6G molecules on Ag (111) have been resolved with concurrent molecular resolution STM images at 19 K. In comparison with the TER spectra at 292 K, the sharpening of TERS peaks and the existence of new peaks at 19 K demonstrates the utility of UHV-TERS towards obtaining site-specific chemical information about adsorbed molecules. This study sets the stage for Raman vibrational fingerprinting and correlated sub-molecular resolution topography of site-specific binding of molecules on solid surfaces.