Adsorption of di- l-alanine on Cu( [formula omitted]) investigated with scanning tunneling microscopy

Abstract

Sub-monolayer growth of a small chiral peptide, di- l-alanine, on Cu(1 1 0) was investigated by variable temperature scanning tunneling microscopy (STM). At low coverage and for temperatures above ≈−220 K the molecules nucleate along the [ 3 ̄ 3 2] direction to form short, mainly one-dimensional islands. An increase in coverage leads to the formation of [ 3 ̄ 3 2]-directed, elongated islands. Images with sub-molecular resolution reveal that the orientation of the molecules within one particular island depends on the deposition temperature. At higher coverage, up to one monolayer, the islands coalesce, giving rise to phase boundaries between domains of opposite orientation. An atomic-scale model for di- l-alanine on Cu(1 1 0) is presented.