Self-Assembled Structures of Glycine on Cu(111)

Adsorption and self-assembly of glycine on the Cu(111) surface are studied by means of scanning tunneling microscopy in an ultrahigh vacuum environment. The results show that the adsorbates are chemisorbed on the surface, may take three different conformations, and can form the 2-D gas phase, the chain phase, and two superstructures (2-D solid phases). Although the chain phase was reported as seen from several other amino acid/Cu(001) systems, a concrete model of it is proposed here for the first time. Besides, detailed models have also been proposed for the two superstructures, for further investigation. Combining the results of the present glycine/Cu(111) system with those obtained previously for the glycine/Cu(110) and -(001) systems, a coherent picture of the behavior of glycine molecules adsorbed on Cu surfaces emerges and is discussed.