Attachment of Organic Molecules to Silicon Utilizing Wet Chemical and Ultrahigh Vacuum Techniques for Molecular Electronics

Christina A. Hacker, Curt A. Richter

Semiconductor Electronics Division

Electronics and Electrical Engineering Laboratory

National Institute of Standards and Technology

Gaithersburg, MD 20899

The understanding of the attachment of organic molecules to the silicon surface is of prime importance for a bottom-up approach to fabricating molecular electronic devices.  Moreover, utilizing the silicon surface as the molecular substrate is more advantageous than self-assembled monolayers (SAMs) on metal surfaces due to the potential for more robust organic monolayers amenable to further processing and resistant to degradation over time.  Unfortunately, the surface chemistry of silicon in solution is more difficult to control leading to monolayers of irreproducible quality with larger time-to-time and lab-to-lab variations.  Although, bench-top wet chemical approaches are more attractive from a technological standpoint, we also utilize ultrahigh vacuum attachment reactions, which are easier to control and capable of creating monolayers of ordered and oriented molecules.  We study the properties of organic monolayers created by both bench-top wet chemical reactions and those created in a controlled, ultrahigh vacuum environment.  Understanding the formation of the monolayer and fabricating a robust, dense, and homogeneous monolayer on silicon is a crucial first step to creating molecular electronic test structures necessary for the development of the metrology for these next-generation devices.