Study on the modulation mechanism of the optoelectronic properties based on common electrode metal atom adsorption on graphene/MoTe2

Abstract

Context

The two-dimensional graphene/MoTe₂ heterostructure holds extensive potential applications in optoelectronic devices, sensors, and catalysts. To expand its optical applications, this study systematically investigates the adsorption stability of metal atoms (Au, Pt, Pd, and Fe) on the graphene/MoTe₂ and their influence on its optoelectronic properties employing first-principles methods. The findings indicate that after the adsorption of Au and Pd, the structure retains its direct bandgap properties, while the adsorption of Pt and Fe exhibits indirect bandgap characteristics. The work functions for all adsorbed structures are lower compared to the pristine graphene/MoTe₂. The total density of states is primarily derived from the C-2p, Mo-4d, Te-5p orbitals, as well as the d and s orbitals of the adsorbed atoms. The pristine graphene/MoTe₂ exhibits significant absorption in the ultraviolet range. Once graphene/MoTe₂ is adsorbed by metal atoms, it can significantly enhance the optical absorption across the spectrum from infrared to ultraviolet light. These findings provide important theoretical guidance for regulating the application of graphene/MoTe₂ in optoelectronics and related fields.

Methods

All analyses are grounded in density functional theory first principles and computed using CASTEP. Graphene/MoTe₂ consists of 4 × 4 × 1 single-layer, graphene single layer, and 3 × 3 × 1 single-layer MoTe₂. To prevent interactions between neighboring unit cells, a 20 Å vacuum space in the z-direction is employed. The electronic exchange–correlation interactions are treated using the Perdew-Burke-Ernzerhof functional within the framework of the generalized gradient approximation. Van der Waals (vdW) interactions are incorporated using the vdW correction function proposed by Grimme, which effectively describes vdW interactions. During the simulation, the cutoff energy for plane wave expansion is set to 420 eV, and the k-point grid is set to 4 × 4 × 1. The atomic displacement convergence standard is 0.002 Å, the internal stress convergence standard is 0.1GPa, and the interaction force convergence standard between atoms is 0.05 eV/Å. The convergence threshold for the iteration precision is set to ensure that the total energy for each atom is not less than 2 × 10⁻⁵ eV/atom.