AVS 45th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS2-TuA

Paper SS2-TuA6
The Chemistry and Formation of Ordered Organic Molecular Films on Silicon (001)-2x1 Surfaces

Tuesday, November 3, 1998, 3:40 pm, Room 309

Session: Morton M. Traum Student Award Session
Presenter: J.S. Hovis, University of Wisconsin, Madison
Authors: J.S. Hovis, University of Wisconsin, Madison
R.J. Hamers, University of Wisconsin, Madison
Correspondent: Click to Email
We have recently developed a novel method for growing ordered organic films on the technologically important Si(001)-2x1 surface. The reaction involves the interaction of a surface Si=Si dimer with a C=C double bond from an unsaturated alkene, resulting in the formation of two new Si-C @sigma@ bonds. Due to the directional nature of @pi@ bonds the Si=Si dimer bond is able to act like a template, controlling the locations and rotational orientation of the individual adsorbed molecules. One unique aspect of this growth method is the fact that the molecules adsorb without dissociation, leading to a well defined interface between the silicon substrate and the organic film. We find that a number of molecules, including cyclopentene, 1,5-cyclooctadiene, and 1,3,5,7-cyclooctatetraene form films that exhibit in-plane optical anisotropies on the length scales of centimeters when adsorbed on 4°-miscut (single-domain) wafers. The molecules 1,5-cyclooctadiene and 1,3,5,7-cyclooctatetraene form monolayers that terminate with ordered arrays of C=C double bonds at the vacuum-surface interface and the ability to grow further layers will be discussed. We have also examined the adsorption of 1,3-cyclohexadiene and 2,3-dimethyl-1,3-butadiene on the Si(001) surface. These molecules can form two different products on the surface; one of which is more thermodynamically favorable. Our studies show that both possible products are formed, indicating that kinetics play a larger role in the adsorption probability than do thermodynamics. Experimental evidence using scanning tunneling microscopy (STM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) will be shown as will the results of ab inito calculations.