Frequency-modulated, single-molecule absorption detected by scanning tunneling microscopy

Erin S. Carmichael, Joshua B. Ballard, Joseph W. Lyding, Martin Gruebele

Research output: Contribution to journalArticlepeer-review


We image frequency-modulated single-molecule optical absorption using a scanning tunneling microscope as the detector (SMA-STM). As a first example of the technique, a semiconducting carbon nanotube adsorbed on a silicon surface is studied. Excitation is achieved using laser amplitude as well as frequency modulation, and these two complementary approaches are compared. Detection is achieved via the resulting change in tunneling current through the excited molecule. We distinguish three mechanisms, direct, relaxed, and bolometric, for detecting single-molecule absorption spectra. Kinetic models for these mechanisms as well as for surface heating are presented. The latter effect can be eliminated by frequency modulation, keeping the laser power density on the surface constant.

Original languageEnglish (US)
Pages (from-to)3314-3321
Number of pages8
JournalJournal of Physical Chemistry C
Issue number8
StatePublished - Mar 1 2007

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Energy
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films


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