A vibrational study of the adsorption of glycine on clean and Na modified Si(100)-2×1 surfaces

The chemisorption of glycine and its fully deuterated analogue, d(5)-glycine, deposited on the clean and Na modified Si(100)-2 x 1 surfaces, has been studied by high-resolution electron energy loss spectroscopy (HREELS) and ab initio methods. HREELS indicates that chemisorption of glycine and d(5)-glycine on Na/Si(100)-2 x 1 occurs through cleavage of the OH and OD bonds in the carboxylic groups. The adsorbed species are bonded through the formation of an ionic bond between the deprotonated carboxylate group and the adsorbed Na atom, leading to species in a bidentate coordination. In contrast, we observe monodentate glycinate and d(5)-glycinate species following the exposure of Si(100)-2 x 1 to glycine and deuterated glycine. The thermal stability of glycine on clean Si(100)-2 x 1 and on the Na modified surface has been studied by heating the substrate to various temperatures. (C) 2002 Elsevier Science B.V. All rights reserved.