Diffusion and incorporation of a surfactant: In on (vicinal) Cu(0 0 1)

We investigate the behaviour of submonolayer amounts of indium at steps and in terraces on Cu(0 0 1) and Cu(1 1 17) surfaces at temperatures between 120 and 300 K by means of variable temperature scanning tunneling microscopy (STM). We find that after deposition all indium atoms attach to steps and that they are eventually incorporated in the first atomic layer to form a surface alloy. At 120 K indium atoms have a clear preference to form rows of specific lengths along steps. At higher temperature the mobility of indium at steps increases, resulting in an apparent decrease in the average length of indium rows. The indium atoms are incorporated in the first layer at room temperature. At the low coverages of our experiment, they exhibit only moderate ordering after being incorporated. To substantiate the picture that emerges from the STM-measurements, we provide a detailed comparison with perturbed angular correlation spectroscopy (PACS) results that have been obtained previously on the same system. When the PACS spectra are partly reinterpreted, the results from both techniques are in agreement and provide the full scenario of the incorporation of indium in Cu(0 0 1) surfaces.