Exotic magnetism in As-doped α/β-In₂Se₃ monolayers with tunable anisotropic carrier mobility

The two-dimensional (2D) material family is expanding fast as novel metal chalcogenides are being continually fabricated and intriguingly, plenty of them are ideal candidates for future nanoscale electronic and magnetic devices. Based on first-principles calculations, we investigated the electronic and magnetic properties of α/β-In₂Se₃ monolayers. We find singularities of density of states appear in the valence band and hole doping (such as a Se atom substituted by a lower valence atom) can induce various ferromagnetic phase transitions in the α/β-In₂Se₃ monolayers. In particular, replacement by arsenic at the anion site can enhance ferromagnetism and drive α-In₂Se₃ to be a robust half-metal and β-In₂Se₃ to be a bipolar magnetic semiconductor. Then, we proposed spin-polarized field-effect transistors based on α-In₂Se₃ and a bipolar field-effect spin-filter based on β-In₂Se₃. Besides, we also discussed the influences of the molecules in air on the device performance such as carrier mobility. We found that the adsorption of either O₂ or H₂O on α/β-In₂Se₃ induced changes in hole mobility in different directions. These findings reveal a new road to electronic and magnetic modulations in 2D materials.