Frank Noll, Bernd Geisler, Norbert Hampp

Institute of Physical Chemistry, Philipps-University, and Materials Science Center, Marburg, Germany

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Summary: Near-contact mode atomic force microscopy (AFM) imaging leads to sharper representations of DNA double strands on mica imaged at ambient conditions compared with noncontact mode AFM. Phase shift was used for feedback control yielding height information using a simple model calculation. No contact between tip and sample occurs. Measured DNA widths were up to four times smaller than measured with the same AFM tip in noncontact mode at ambient condition.

Key words: atomic force microscopy, near-contact, phase-shift, DNA, noncontact

PACS: 07.79.Lh, 87.14.Gg, 87.64.Dz