The Mechanism for the Thermally Driven Self-Assembly of Pyrazine into Ordered Lines on Si(100)

The chemisorption of pyrazine on Si(100) is a unique and experimentally demonstrated example for the growth of an ordered ID line of organic molecules on a very reactive silicon surface. Two key factors are identified, using first principles calculations, as being responsible for this remarkable process. First, van der Waals interaction between pyrazine and Si(100) varies considerably depending on the orientation of a pyrazine molecule, which opens up a significant gap in the activation barriers and makes the adsorption selective. Second, the presence of multiple reaction channels at elevated temperature could actually facilitate the self-assembly of adsorbed molecules into ordered structure, due to the presence of a cooperative effect. Consideration of these two factors should be useful in the search for other organic molecules to grow 1D lines on clean silicon surfaces.