The puzzle of contrast inversion in DNA STM imaging

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DNA has been at the center of an imaging effort since the invention of the scanning tunneling microscope (STM). In some of the STM imaging reports the molecules appeared with negative contrast, i.e., "submerged" under the metal background and darker. We demonstrate the phenomenon of contrast inversion in DNA STM imaging by controlled and spontaneous contrast inversions and by the dependence of the DNA apparent height with respect to the surface on the imaging bias voltage. Using these characterizations, we formulate a model explaining the above phenomenon by resonant tunneling through virtual states in the vacuum between the STM tip and the DNA molecule.


Original languageEnglish
Pages (from-to)14270-14274
Number of pages5
JournalJournal of Physical Chemistry B
Issue number30
Publication statusPublished - 4 Aug 2005

External IDs

PubMed 16852793
Scopus 23844483925