ADSORPTION OF Cu, Ni AND Fe ATOMS ONTO WSe2 MONOLAYER: A DFT STUDY

Abstract

The adsorption of 3d transition metal (TM) atoms like Cu, Ni, and Fe on the WSe2 monolayer was investigated using first-principal calculations, specifically Density Functional Theory (DFT), which is a powerful computational approach to understand the adsorption phenomenon at the atomic level comprehensively. This study reveals that the adsorption of these TM atoms enhances the overall properties of the monolayer by affecting its geometry, adsorption energy, and electronic and magnetic properties. DFT provides insights into the changes induced by the adsorbates. Calculations were performed using the Generalized Gradient Approximation and ultrasoft pseudopotentials, evaluating three adsorption sites (H, TW, and TSe) on the monolayer. The optimal adsorption site was determined by calculating the adsorption energy for each optimized configuration. The results showed that Cu and Ni atoms prefer the TW site, with adsorption energies of -3.05 eV and -4.72 eV, respectively, while Fe prefers the H site with an adsorption energy of -4.37 eV. These high adsorption energies indicate strong chemical adsorption, suggesting covalent bonding between the atoms and the monolayer, which significantly influences the WSe2 monolayer's geometry and modifies its electronic and magnetic properties. A key objective was to investigate how TM atom adsorption alters the optical and electronic properties of the WSe2 monolayer, enhancing its suitability for optoelectronic and spintronic applications. Electronic parameters such as the density of states (DOS), projected density of states (PDOS), and charge transfer were analyzed. DOS analysis revealed that the pristine WSe2 monolayer, which has a band gap of 1.27 eV, undergoes significant band gap reduction upon TM atom adsorption. Specifically, Cu and Fe adsorption closed the band gap entirely, transforming the WSe2 monolayer into a metallic state. In contrast, Ni adsorption reduced the band gap to 0.88 eV, indicating a transition to a narrower band gap semiconductor. This band gap modulation is crucial for tuning the electronic properties of WSe2 for various device applications. The study also observed shifts in the Fermi energy level upon TM atom adsorption, indicating substantial changes in the monolayer's electronic structure. PDOS analysis provided more profound insights into the interactions between the TM atoms and the WSe2 monolayer, showing significant hybridization between the 3d orbitals of the TM atoms, the 5d orbitals of W, and the 4p orbitals of Se. This strong orbital hybridization indicates robust chemical bonding, which is responsible for the variations in electronic properties. Charge density difference calculations supported these findings, showing considerable charge transfer from the TM atoms to the WSe2 monolayer. This is a critical factor in band gap narrowing and the transition to metallic behavior. The adsorption of Cu, Ni, and vii Fe on the WSe2 monolayer enhances its electronic properties and induces magnetic properties due to the presence of unpaired d-electrons in these transition metals. This is particularly advantageous for spintronic applications, where control of spin-dependent properties is essential. The detailed understanding of the adsorption mechanism provided by this study highlights the potential of TM-doped WSe2 monolayers as multifunctional materials engineered for specific optoelectronic and spintronic applications. The ability to modulate the band gap and introduce metallic behavior through TM atom adsorption opens new opportunities for designing devices with tailored electronic properties. Additionally, the observed changes in the Fermi level and strong covalent bonding emphasize the potential for stable and efficient material performance in practical applications. In conclusion, this study thoroughly analyses Cu, Ni, and Fe atom adsorption on the WSe2 monolayer using DFT. The results demonstrate significant enhancements in the monolayer's electronic and magnetic properties due to strong chemical bonding and charge transfer from the adsorbates. The modulation of the band gap and the transition to metallic behavior upon TM atom adsorption suggest that TM-doped WSe2 monolayers are promising candidates for advanced optoelectronic and spintronic devices. These insights can guide future experimental and theoretical research to optimize the properties of TMD-based materials for a wide range of technological applications.