Formation of atomic Pt chains on Ge(001) studied tunneling microscopy

Recently, it was found that atomic Pt chains can be grown on Ge(001) surfaces. These kink-free wires only grow on specific Pt-modified, so-called beta terraces, which are one atom wide and up to a micron long. Their self-assembly includes a crucial, high-temperature annealing step, following low-temperature (sub-) monolayer deposition. So far, details of the formation process remained unclarified. Here, we report on the formation of the Pt atomic chains on the Ge(001) surface after a high-temperature annealing at 1100 K. The results suggest that at high temperature, the platinum, previously submerged during and after deposition, emerges and forms Pt dimers located in the troughs between the surface dimer rows, which locally widen in this process. These Pt dimers are initially oriented parallel to the substrate dimers. However, upon surpassing a critical local coverage, the Pt dimers rotate by 90°, resulting in a zipperlike formation of the Pt chains.