Effect of Mn-Doping and Strain on Electronic and Magnetic Properties of MoSe₂
Owen Fauth ’23 Professor Leah Bendavid (Chemistry)
Transition metal dichalcogenides (TMDs) have recently become the focus of increased attention for their use as two-dimensional materials in digital electronic and spintronic applications. Their properties can potentially be modified and optimized for specific applications via doping or applying strain. The purpose of this study is to observe the effects of substitutional Mn-doping and strain on the magnetic, optical, and electronic properties of a monolayer of MoSe₂. Specifically, this investigation monitored the sensitivity of the band gap, the magnitude of the local magnetic moments, and the driving force for ferromagnetic ordering. Compressive and tensile strains of up to 15% were applied, and the monolayers were doped at concentrations of 6.25% and 12.5%. This study was done with density functional theory (DFT) calculations using the PBE and HSE exchange-correlation functionals. We found that the band gap tended to decrease in magnitude with increasing percentages of both compressive and tensile strain; this pattern was observed with and without Mn-doping. Pure MoSe2 is a direct-gap semiconductor, but PBE predicted that most doped structures would behave as a half-metal, with a transition to fully metallic with increased compressive and tensile strain. HSE predictions retained semiconductor character for many of the structures, with a transition to metallic character with increased compressive and tensile strain. Additionally, we found that the local magnetic moments on the Mn dopants increased with increasing tensile strain or decreasing compressive strain. There is also a consistent energetic driving force for ferromagnetic ordering relative to antiferromagnetic ordering, with an increased energetic difference at increased tensile strain (and decreased compressive strain). Our study demonstrates the potential for engineering Mn-doped MoSe2 semiconductors with tailored magnetic and electronic properties.