adatomsubstrate

An adatom is an atom that resides on the surface of a solid, bonded to the substrate but not part of its crystal lattice. The adatom-substrate system describes the interaction between the adsorbed atom and the underlying material, determining where the atom sits, how strongly it is bound, and how it moves on the surface. These systems are central to surface science and influence phenomena such as catalysis, epitaxial growth, and nanoscale device fabrication.

Key properties include the adsorption energy, preferred binding site (on-top, bridge, or hollow positions on a crystalline surface), and the diffusion barrier that controls mobility. The electronic structure at the adatom-substrate interface can involve charge transfer, hybridization with substrate states, and modifications to the substrate's work function and surface states. Substrate properties such as lattice constant, electronic structure, and surface reconstruction strongly affect adatom behavior, as does strain from lattice mismatch in epitaxial systems. Adsorbate-substrate interactions can also be influenced by temperature, coverage, and the presence of co-adsorbates.

Experimental techniques used to study adatom-substrate systems include scanning tunneling microscopy and atomic force microscopy, low-energy electron diffraction, X-ray photoelectron spectroscopy, and temperature-programmed desorption. Theoretical investigations typically employ density functional theory and other quantum-chemical methods to map potential energy surfaces, binding energies, and diffusion pathways.

Understanding adatom-substrate interactions informs the design of catalytic surfaces, single-atom catalysts, and controlled growth of nanostructures on metals, semiconductors, and two-dimensional materials such as graphene. It also underpins studies of diffusion, clustering, and island formation critical to materials science and surface engineering.