STM study of d-alanine adsorption on Cu(0Â 0Â 1)

The adsorption of d-alanine on Cu(0 0 1) surface at low coverage was studied by a scanning tunneling microscope. d-alanine forms a c(2 × 4) ordered structure with the arrays aligned dominantly to 〈3 1 0〉 direction on the Cu(0 0 1), and the molecules slightly interact also to 〈1 1 0〉 and 〈1 3 0〉 directions. It suggests that these anisotropic arrays are organized by the intermolecular interaction due to hydrogen bonding between adjacent d-alanines. The proposed model for adsorbed structure as a tridentate form in nearly atop sites is consistent with the recent study for glycine adsorption on Cu(1 0 0) by photoelectron diffraction.