[Paper Review] Effect of Fe-doping on VS2 monolayer: A first-principles study

Mirali Jafari, Nasim Rahmani-Ivriq+1 more|arXiv (Cornell University)|Nov 18, 2024

Metal and Thin Film Mechanics4 citations

TL;DR

This first-principles DFT study investigates Fe-doping effects on VS₂ monolayer, revealing significant modifications in electronic structure, magnetic anisotropy energy (MAE), and optical response. Fe-doping induces metallic or half-metallic behavior, enhances MAE, and enables tunable anisotropic optical properties, enabling applications in spintronics and optoelectronics.

ABSTRACT

Transition metal dichalcogenides (TMDs), like VS2, display unique electronic, magnetic, and optical properties, making them promising for spintronic and optoelectronic applications. Using first-principles calculations based on the Density Functional Theory (DFT), we study the effect of Fe-doping on the electronic and magnetic properties of a VS2 monolayer. The pristine VS2 monolayer has ferromagnetic order and a small energy bandgap. This work aims to comprehensively study the substitution of selected Vanadium atoms in the VS2 monolayer by Iron (Fe) atoms, where the substitution concerns Vanadium atoms at various sites within the 2x2 and 3x3 supercells. This leads to significant modifications of the electronic band structure, magnetic anisotropy energy (MAE), and optical response (e.g., dielectric constant and absorption coefficient). The results provide valuable insights into engineering the VS2 monolayer properties for future applications, ranging from spintronics to cancer therapy in medical science.

Motivation & Objective

• To investigate the impact of Fe-doping on the electronic and magnetic properties of VS₂ monolayer using first-principles calculations.
• To explore how Fe-dopant distribution in 2x2 and 3x3 supercells alters magnetic anisotropy energy (MAE) and band structure.
• To analyze the modification of optical properties, including dielectric function and absorption coefficient, due to Fe-doping.
• To evaluate the potential of Fe-doped VS₂ for applications in spintronics, optoelectronics, and biomedical fields such as cancer therapy.
• To provide a comprehensive understanding of defect-induced magnetic and electronic transitions in 2D TMDs through controlled doping.

Proposed method

• Employed density functional theory (DFT) with PBE+U and spin-orbit coupling (SOC) to account for electron correlation and relativistic effects.
• Constructed 2x2 and 3x3 supercells of VS₂ monolayer to model Fe-doping at various V-site positions, ensuring periodic boundary conditions.
• Calculated magnetic moments of V and Fe atoms and analyzed their dependence on dopant distribution and supercell geometry.
• Used the Kubo-Greenwood formula to compute optical properties, including dielectric function, reflectivity, and extinction coefficient.
• Analyzed band structure, density of states, and magnetic anisotropy energy (MAE) to assess magnetic ordering and spin-polarization.
• Compared pristine VS₂ with Fe-doped configurations to identify trends in band gap reduction, metallic transition, and optical response modulation.

Figure 1: Schematic structure of the VS 2 monolayer without and with Fe-doping: (a) Side view and (b) top view of the pure VS 2 primitive cell, (c,d) Fe-doping at various sites within 2x2 and 3x3 VS 2 supercells.

Experimental results

Research questions

• RQ1 How does Fe-doping at different V-site positions in VS₂ monolayer affect the electronic band structure and magnetic properties?
• RQ2 What is the impact of Fe-dopant concentration and spatial distribution on the magnetic anisotropy energy (MAE) in VS₂ monolayer?
• RQ3 How does Fe-doping modify the dielectric function and absorption coefficient, particularly in terms of anisotropy and optical response?
• RQ4 Can Fe-doping induce a transition from semiconducting to metallic or half-metallic behavior in VS₂ monolayer?
• RQ5 To what extent can the optical and magnetic properties of VS₂ be tuned via controlled Fe-doping for spintronic and optoelectronic applications?

Key findings

• Fe-doping in VS₂ monolayer leads to a complete suppression of the band gap in certain configurations, transforming the system into a metallic or half-metallic state due to hybridization between Fe-d orbitals and the host lattice.
• The magnetic anisotropy energy (MAE) increases significantly in Fe-doped configurations, particularly in 3x3 supercells with specific Fe-dopant arrangements, indicating enhanced out-of-plane magnetic ordering.
• The real part of the dielectric constant (εr) exhibits a pronounced initial peak in Fe-doped VS₂ (e.g., 3x3 sites-3,4), contrasting with the gradual rise in pristine VS₂, indicating strong modification of electronic excitations.
• Anisotropic optical response is observed in Fe-doped VS₂ (3x3 sites-3,4), with distinct values of εxx, εyy, and εyx, indicating preferential alignment of Fe dopants and directional dependence in optical absorption.
• The absorption coefficient (α) shows strong anisotropy in specific Fe-doped configurations, with enhanced optical transitions in the 1–2 eV range, suggesting tunable optoelectronic response.
• The results demonstrate that selective Fe-doping enables precise engineering of electronic, magnetic, and optical properties, supporting potential applications in spintronics, optoelectronics, and biomedical fields such as cancer therapy.

Figure 2: Distribution of iron (Fe) atoms according to the supercell and the substituting positions and corresponding Brillouin zones.