Molecular Rulers  - Conquering the World of Nanofabrication:
One Molecule at a Time

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434 Davey Lab Penn State University Contacts: Paul S. Weiss: stm@psu.edu Beth Anderson: mea151@psu.edu Morgan Mihok: mxm571@psu.edu Jackie Tan: lxt139@psu.edu  Hiro Tanaka: hxt@stm1.chem.psu.edu

Picture (from left to right): Jackie, Beth, The Dipper (Lab Robot), Morgan

We have developed a method that combines conventional lithographic techniques and chemical self-assembly processes to create gaps and nanostructures with nanometer-scale resolution.  The chemical process creates a three-dimensional molecular resist composed of alternating organic molecule and metal ion coordinated multilayers of mercaptoalkanoic acid (HS(CH₂)_xCOOH) and Cu²⁺ ions.  The molecules composing the self-assembled multilayers can be used as molecular rulers to control precisely and quantitatively the size of the created structures.  Dimensions of the spacings between the parent and daughter structures can be customized with widths ranging from 10–100 nm, although even precise spacings below 10 nm should be possible.  The iterative nature of this procedure has been automated by the Lab Robot (Varistain Gemini Slide Stainer) shown above. 

Molecular Ruler Assembly Process (not to scale)  a) Lithographically defined gold parent structures deposited on insulating SiO2 substrate.  b) Molecular rulers, alternating layers of mercaptoalkanoic acid (HS(CH2)xCOOH) and Cu2+ ions, serve as the molecular resist to mask the parents. c) Daughter metal is evaporated.  d) A precisely defined patterned daughter structure remains after chemical lift-off of the molecular resist.

References:

Hatzor, A. and P.S. Weiss, Science, 291, 1019 (2001).
Anderson, M.E. et.al., J. Vac. Sci. Technol. B, 20, 2739 (2002).

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