AVS 51st International Symposium
    Nanometer-scale Science and Technology Wednesday Sessions
       Session NS-WeM

Paper NS-WeM10
Thermal Control in Dip Pen Nanolithography

Wednesday, November 17, 2004, 11:20 am, Room 213D

Session: Nanoscale Patterning and Lithography
Presenter: P.E. Sheehan, Naval Research Laboratory
Authors: P.E. Sheehan, Naval Research Laboratory
W.P. King, Georgia Tech
L.J. Whitman, Naval Research Laboratory
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Although it has been widely assumed that Dip Pen Nanolithography (DPN) requires a water meniscus to tranfer ink from an AFM tip to a surface, we have shown that transfer can occur under xeric conditions@footnote 1@ , a method we call "dry deposition". Our recent studies of dry deposition have led to a number of insights into how DPN can be extended beyond "wet" inks. For example, deposition should be possible at high temperatures (i.e., above the boiling point of water) and, thus, temperature could be used to control deposition. We have utilized a heated atomic force microscope (AFM) cantilever tip to control the deposition of a solid organic ink. The ink, octadecylphosphonic acid (OPA), melts at 98°C and self-assembles on mica, the substrate. Evaporation was used to coat OPA onto a cantilever with integrated microheaters. When the cantilever temperature was below 98°C, no deposition was detected. At 98°C slow deposition was seen, but only after raising the temperature to 122° C was deposition robust. Thermal DPN (tDN) enhances traditional DPN in many ways. First, it allows exquisite control over writing--deposition may be turned on or off and the deposition rate changed without breaking contact with the surface. Secondly, the inks used have lower surface mobilities once cooled and so are able to achieve higher spatial resolution. Thirdly, imaging with a cool tip does not appear to contaminate the surface. This allows in situ confirmation of the deposited pattern without fear of contamination. Finally, tDPN expands the range of useable inks--current work with electronically active molecules that have high melting temperatures will be presented. @FootnoteText@ @footnote 1@ PRL 88, 156104 (2002).