Infrared spectroscopy of molecular submonolayers on surfaces by infrared scanning tunneling microscopy: Tetramantane on Au(111)

Ivan V. Pechenezhskiy, Xiaoping Hong, Giang D. Nguyen, Jeremy E.P. Dahl, Robert M.K. Carlson, Feng Wang, Michael F. Crommie

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

We have developed a new scanning-tunneling-microscopy-based spectroscopy technique to characterize infrared (IR) absorption of submonolayers of molecules on conducting crystals. The technique employs a scanning tunneling microscope as a precise detector to measure the expansion of a molecule-decorated crystal that is irradiated by IR light from a tunable laser source. Using this technique, we obtain the IR absorption spectra of [121]tetramantane and [123]tetramantane on Au(111). Significant differences between the IR spectra for these two isomers show the power of this new technique to differentiate chemical structures even when single-molecule-resolved scanning tunneling microscopy (STM) images look quite similar. Furthermore, the new technique was found to yield significantly better spectral resolution than STM-based inelastic electron tunneling spectroscopy, and to allow determination of optical absorption cross sections. Compared to IR spectroscopy of bulk tetramantane powders, infrared scanning tunneling microscopy (IRSTM) spectra reveal narrower and blueshifted vibrational peaks for an ordered tetramantane adlayer. Differences between bulk and surface tetramantane vibrational spectra are explained via molecule-molecule interactions.

Original languageEnglish (US)
Article number126101
JournalPhysical Review Letters
Volume111
Issue number12
DOIs
StatePublished - Sep 16 2013
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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