STM study of dl-alanine array structure on Cu(0 0 1)

The effect of molecular chirality of alanine molecule on the two dimensional ordering on Cu(0 0 1) surface has been studied by high resolution scanning tunneling microscope. It is identified that in the antiphase c(2 × 4) domains on the terraces, two bright spots with different shape, corresponding to each alanine molecule, form chains along [1̄ 3 0] or [3̄ 1 0] direction. Their orientation changes at the domain boundaries along [1 1 0] direction from [1̄ 3 0] to [3̄ 1 0] direction in accord with the difference in the direction of intermolecular NH–O2 hydrogen bonds depending on the chirality of alanine molecule in the c(2 × 4) ordered structure. This agrees well that d- and l-alanine molecules segregate to form their own c(2 × 4) domains separated by the [1 1 0] boundary lines.