Layer-Resolved Spin and Charge Interplay in H-, Ag-, and Au-Adsorbed Si(111) Surfaces: Insights into Metallicity and Magnetism

This study investigates the electronic and magnetic properties of H-, Ag-, and Au-adsorbed Si(111) surfaces across single-layer (1L), bilayer (2L), trilayer (3L), and four-layer (4L) configurations using density functional theory (DFT) calculations. We considered a new Si(111) configuration, which is semiconducting with a 1.19 eV band gap, slightly differing from its counterpart, the metallic Si(111). All H/Si(111) structures are semiconductors with a band gap in the range of 1.00 to 2.03 eV. Ag has a less pronounced effect on the semiconducting behavior, maintaining reduced band gaps, while Au induces metallicity and strong spin polarization, especially in 2L and 3L systems. The magnetic character in Au/Si(111) arises from significant contributions of d-orbitals, promoting electron delocalization and structural strain. These findings highlight a clear relationship between layer thickness and electronic properties, with increased stability in multilayer configurations. These results provide valuable insights into the interplay between metal adsorption and electronic structure, with promising implications for spintronic and catalytic applications.