Amino acid adsorption on the Si(100) surface: The case of glycine

Using first principles total energy methods, we have investigated the adsorption of glycine-the simplest amino acid-on the Si(100)- c(4 x 2)surface, with a focus on the associated energetics, charge transfer, electronic properties, and structural characteristics. We find that glycine adsorbs primarily on the "down" atoms of a Si dimer, with adsorption of the amino group being slightly favored over the absorption of the carboxylic acid group. Glycine on Si(100) may also involve the removal of a H atom from the chemical Group most directly absorbed. In addition. there is evidence for a [2 + 2] cycloaddition reaction when both "C=O" atoms absorb, as well as the more drastic breakup of the glycine molecule and the formation of a ketenimine molecule under high-energy conditions.