Arrangement of Au-Si alloy islands at atomic steps

We show using low-energy electron microscopy that Au deposition at around 400 °C leads to the arrangement of three-dimensional islands at single-layer steps on Si(1 1 1). Because the islands nucleate within a narrow coverage window, they have a small size distribution. After the coarsening of the islands during the interruption of the Au deposition, further deposition of Au results in the motion of islands into upper terraces with trenches left behind. This indicates that the islands are Au-Si alloy droplets. Additionally, the islands moved on terraces almost at constant velocities, but when they approach the upper-side steps, they jumped up to the steps. The atomic steps provide stable positions for Au-Si alloy islands, which means that the Au-Si alloy islands are suitable for arrangement using atomic steps.