THE GROWTH AND ATOMIC-STRUCTURE OF THALLIUM ON COPPER(001)

We report a determination of the room temperature growth and atomic st ructure of ultrathin films of thallium on copper(001) using surface X- ray diffraction. The results show clearly that the growth is layerwise up to two monolayers and islanded thereafter. This is contrary to ear lier reports which suggested that the islanding commenced at one monol ayer. The first submonolayer structure to appear is a c(4 x 4) arrange ment. Reflectivity scans suggest that there is significant reordering of the substrate at this coverage.