Probing down to the atomic scale the size-dependent electronic and magnetic properties of few-atom clusters

Consider a particle that consists of only ten atoms and that is deposited on a metal, semiconductor, or insulator surface. What will be the most stable structure of such a particle and how will this structure be affected by the underlying substrate? What are its corresponding electronic and magnetic properties? How do these properties depend on the exact number of atoms in the particle? These all are fundamental questions that scientists have been struggling with for decades. Small clusters or nanoparticles are potential building blocks for future applications such as spintronics and quantum computing. In this project we will focus on ultra-small clusters composed of one or two types of elements with only two to a few tens of atoms (e.g., Au clusters, Co clusters, B clusters, and MoS2). In the recently developed cluster beam deposition apparatus, the clusters first will be mass-selected in the gas phase with atomic precision and then deposited on atomically flat surfaces, including metallic substrates that are covered with a thin insulating layer. By combination of cryogenic (spin-polarized) scanning tunneling microscopy experiments under clean vacuum conditions and simulations based on density functional theory, we will investigate the structural, electronic, and magnetic properties of the deposited clusters, and we will examine how these properties depend on the number of atoms the cluster is composed of as well as on the selected substrate.