Computational surface chemistry of glycine on Si(1 1 1)7×7 and Si(1 0 0)2×1: Dissociative adsorption through adduct formation

Glycine adsorption on Si(1 1 1)7×7 and Si(1 0 0)2×1 model surfaces are studied by using Density Functional Theory (DFT) calculations. The present work illustrates that the formation of different surface adducts involving the –NH2 and –COOH functional groups plays a vital role in determining the adsorbate structures on the 7×7 and 2×1 surfaces. No Si ← O surface adduct can be obtained on Si(1 1 1)7×7, in marked contrast to Si(1 0 0)2×1, on which the formation of Si–O bond readily leads to O–H dissociative product. For Si(1 1 1)7×7, the existence of only Si ← N adduct leads to N–H dissociative product and the formation of Si–N bond. These results are in good agreement with the experiment.