Substitutional Tungsten Doping in Silicon Carbide Introducing Magnetic Properties: A Computational DFT Approach

Abstract

Background: Small concentration of magnetic material, in general, the transition metal atoms (TM), when doped into a semiconductor, behaves as a diluted magnetic semiconductor (DMS). It has an application to Quantum computing & spintronic devices. DMS silicon carbide has strong coupling and high Curie temperature. The magnetic and electronic properties of SiC with TMs impurities have been in focus for theoretical and experimental researchers. Objective: The objective of this work is to study the electrical and magnetic properties of tungsten doped cubic SiC. Comparing the density of states plot with and without impurity, the change in property happening due to the presence of tungsten is observed. Partial density of states is also plotted and interpreted. Self-consistent spin polarized calculations are done to study the magnetic properties. Magnetic Moment is also calculated for substitutional doping of SiC at different sites. Methods: Tungsten doped 3C-SiC is investigated by using the first-principle energy code, Quantum Espresso, which uses pseudopotential within Density Functional Theory (DFT). The calculations are done by density functional pseudopotential energy calculations in periodic systems by solving iteratively the Kohn Sham equation in a plane wave basis set. Both norm conserving and Vanderbilt USPP are used. Self-consistent iterations were performed until convergence of total energy and total charge was obtained. We used different k-point meshes for different supercells with 16, 54 and 128 atoms giving results for carious impurity percentages. Results: The formation energy values obtained indicate that the W impurity prefers the Si site to the C site in cubic SiC. The presence of a narrow band towards the conduction band minimum is due to the W-d states for Si site substitution. Both spin-up and spin-down states contribute towards the valence band, and a small contribution goes towards the conduction band. The magnetic moment values for C site substitution are lower than Si site substitution. Conclusion: It is observed W doped with Si site of cubic silicon carbide shows ferromagnetic behavior. Hence, there is a possibility of 3C SiC doped with W at the C site to behave as a semi-insulating material.