The Cu3Au(001) surface: a He diffraction study

We present the results of a helium diffraction study of the morphology of a Cu3Au(001) surface at 140 K. Biatomic steps only are not able to describe the terrace morphology, and monoatomic steps must be included. The step hei ght (1.855 +/- 0.015 Angstrom) is closely comparable to the bulk interlayer spacing of Cu3Au along the (001) direction (1.865 Angstrom). Two kinds of terraces have been identified. The first class (A-terraces) are the majorit y. They are large terraces that display the well-known c(2 x 2) ordering of the Au-Cu termination. The second type (B-terraces) consists of much small er terraces of uncertain composition. B-terraces are separated from A-terra ces by a monoatomic step. Monoatomic steps are probably bunched into pairs. (C) 1999 Elsevier Science B.V. All rights reserved.