NANOTRANSFER PRINTING TO FORM RELIABLE SILICON-BASED MOLECULAR ELECTRONIC STRUCTURES

 

M. Coll1, L.H. Miller1, L.J. Richter1, D.R. Hines2, C.A. Richter1 and C.A. Hacker1

1Electronics and Electrical Engineering Laboratory, NIST Gaithersburg, MD 20899.

2Laboratory for Physical Science, University of Maryland, College Park, MD 20740

 

The use of organic molecules anchored on silicon platform is a promising technological concept with fast growing interest for computational applications. Molecules offer small size, flexibility and advanced functionality. Molecular electronic devices based on silicon can capitalize on the extensive Si- device technology fabrication expertise to fabricate molecule-based devices that are embedded on the chip along with conventional electronic devices. This not only reduces development time but also speeds integration of molecule-based devices with conventional CMOS technology.  However, the critical step to molecular state electronics is applying the metal top electrode. Direct vapor-deposition of the metal results in metal penetration through the molecular structure producing electrical shorts and monolayer degradation. Nanotransfer printing (nTP) is a soft-lithography technique that provides a simple and low cost route to fabricate metallic nanostructures at desired locations. Successful transfer printing process usually requires heat and pressure as mechanisms to facilitate material transfer.

We present a novel route to obtain metal-molecule-silicon electronic junctions based on first forming self-assembled monolayers on ultrasmooth gold on plastic substrates and then utilizing nTP to bond the molecular layer to the silicon electrode. To ensure the anchoring of molecules to both the metal and the semiconductor we have utilized bifunctional molecules. We have explored the influence of pressure and temperature on molecular conformation and interfacial reactions in the metal-molecule-silicon sandwich structure. This approach allows the formation of dense bifunctional monolayers preserving the integrity of the molecules within the junction. We demonstrate that molecules bond covalently to both electrodes leading to robust monolayers. The monolayers are characterized prior to formation of the sandwich structure by using infrared spectroscopy, spectroscopic ellipsometry, and scanning probe microscopy. Following formation of the metal-molecule-silicon structure, backside incident FTIR has been used to characterize these nanoelectronic device structures. Our study provides a reliable and facile way to fabricate many molecular electronic structures in parallel allowing careful study of the electrical properties of the organic monolayers.

         

           Category:  Materials

Mentors Name: Christina A. Hacker

Semiconductor Electronics Division, EEEL

A361, Building 225, Mail stop 8120

Tel: (301) 975-2390

Fax: (301) 975-8069

Email:mcollbau@nist.gov

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