Revealing the Electrical and Optical Response of Au Adsorption on SnC Monolayer: An Ab‐Initio Study

ABSTRACT We investigate how gold (Au) adsorption modifies the electronic and optical properties of a 2D SnC monolayer using first‐principles density functional theory (DFT). Structural optimization and electronic calculations are carried out within the FP‐LAPW method using GGA+U and spin–orbit coupling. Pristine SnC shows an indirect bandgap of ≈1.07 eV and a direct gap of ≈1.77 eV. When Au is adsorbed at either the top (T) or bridge (B) site, the bandgap disappears and the system becomes metallic. The adsorption energies, −2.41 eV (T‐site) and −2.68 eV (B‐site), indicate that both sites are thermodynamically stable, with the B‐site slightly more favorable. Optical calculations show clear signatures of metallic behavior. The static dielectric constants are about 16.0 (T‐site) and 15.0 (B‐site), and the corresponding static refractive indices are roughly 3.5 and 3.2. Strong hybridization near the Fermi level enhances optical activity, producing high absorption coefficients of the order of 10⁵ cm −1 in the ultraviolet region. Reflectivity spectra and the energy‐loss function further confirm the presence of free‐carrier features, with plasmon peaks near 0.92 eV (T‐site) and 0.91 eV (B‐site). Overall, Au adsorption strongly alters the semiconducting nature of SnC and produces a metallic optical response. These results highlight the potential of Au/SnC heterostructures for optoelectronic and plasmonic applications, including photodetectors, light‐emitting devices, solar‐energy components, and UV–protective coatings.