Determination of the local structure of glycine adsorbed on Cu(110)

Abstract

Scanned-energy mode N 1s and O 1s photoelectron diffraction has been used to determine the local geometry of glycine adsorbed on Cu(110) in an ordered (3 × 2) phase. The results are consistent with a molecular geometry in which the CC axis lies approximately parallel to the surface and the molecule bonds across a pair of [110] Cu surface rows through the two oxygen atoms of the carboxyl group and the N atom of the amino group. The N atom is displaced by 0.24 ± 0.10 A ̊ off an atop site along the [11̄0] rows with a CuN nearest-neighbour distance of 2.04 ± 0.02 A ̊ . The carboxyl bonds to two Cu atoms in a [11̄0] row, with the O atoms displaced 0.80 ± 0.07 A ̊ from atop in [001] towards the amino group with a CuO nearest-neighbour bond length of 2.03 ± 0.03 A ̊ and a resulting tilt of the OCu bond relative to the surface normal of 23 ± 2°. A specific structural model comprising two molecular moieties per unit mesh which has the space group p1g1, consistent with the qualitative LEED observations, is proposed on the basis of these data.