Abstract
Dilute magnetic semiconductors (DMS), achieved through substitutional doping of spin‐polarized transition metals into semiconducting systems, enable experimental modulation of spin dynamics in ways that hold great promise for novel magneto–electric or magneto–optical devices, especially for two‐dimensional (2D) systems such as transition metal dichalcogenides that accentuate interactions and activate valley degrees of freedom. Practical applications of 2D magnetism will likely require room‐temperature operation, air stability, and (for magnetic semiconductors) the ability to achieve optimal doping levels without dopant aggregation. Here, room‐temperature ferromagnetic order obtained in semiconducting vanadium‐doped tungsten disulfide monolayers produced by a reliable single‐step film sulfidation method across an exceptionally wide range of vanadium concentrations, up to 12 at% with minimal dopant aggregation, is described. These monolayers develop p‐type transport as a function of vanadium incorporation and rapidly reach ambipolarity. Ferromagnetism peaks at an intermediate vanadium concentration of ~2 at% and decreases for higher concentrations, which is consistent with quenching due to orbital hybridization at closer vanadium–vanadium spacings, as supported by transmission electron microscopy, magnetometry, and first‐principles calculations. Room‐temperature 2D‐DMS provide a new component to expand the functional scope of van der Waals heterostructures and bring semiconducting magnetic 2D heterostructures into the realm of practical application.
Highlights
Dilute magnetic semiconductors, achieved through substitutional doping of spinpolarized transition metals into semiconducting systems, enable experimental modulation of spin dynamics in ways that hold great promise for novel magneto-electric or magnetooptical devices, especially for two-dimensional systems such as transition metal dichalcogenides that accentuate interactions and activate valley degrees of freedom
Ferromagnetism peaks at an intermediate vanadium concentration of a few atomic percent and decreases for higher concentrations, which is consistent with quenching due to orbital hybridization at closer vanadium-vanadium spacings, as supported by transmission electron microscopy, magnetometry and first-principles calculations
Room-temperature two-dimensional dilute magnetic semiconductors provide a new component to expand the functional scope of van der Waals heterostructures and bring semiconducting magnetic 2D heterostructures them into the realm of practical application
Summary
Section Synthesis of pristine and vanadium doped WS2 monolayers: 0.05 g ammonium metatungstate ((NH4)6H2W12O40 · xH2O, AMT) and 0.2 g sodium cholate (C24H39NaO5 · xH2O) powders were dissolved in 10 ml water to form a tungsten precursor solution. 0.05g vanadyl sulfate (VO[SO4]) powder were dissolved in 10mL deionized water to form vanadium precursor (1x10-2 mol/L). The film sulfidation process was carried out at atmospheric pressure in a quartz reaction tube (1” inner diameter) with sulfur powder (400 mg) heated upstream at low temperature (220 °C, heated up using a heating tape), and the cation precursor, spin-coated on the SiO2/Si substrates, at the high temperature (825 °C) zone. Atomic resolution STEM image simulations were conducted by using the QSTEM package[37], the case of vanadium dopant coupled with sulfur monovacancy is set to be three symmetric neighboring sulfur monovacancies in the crystal structure to simplify the simulation process. The probe is mechanically delayed in time, and monitors the change in reflectivity due to the pump-induced heating event (i.e., thermoreflectivity) as a function of delay time.
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