Plasma-Assisted Bipolarity Carrier Modulation in TMDs to Accelerate Dipole Polarization for Enhanced Electromagnetic Attenuation

The bipolarity carrier control of transition metal dichalcogenide (TMDs) absorber is an intriguing method for modulating electromagnetic wave (EMW) absorption properties. While broadband gap tunability in TMDs suggests potential for optimized electromagnetic (EM) response, the prevalent n-type unipolarity, stemming from strong electronic doping, has hindered exploration of the impact of carrier polarity. There is also an urgent need to explore efficient methods for regulating carrier polarity in TMDs. Here, an innovative strategy is proposed based on dual plasma-assisted group IIIA elements (In, Al) to regulate the carrier bipolarity of TMDs. Through experiments and theoretical simulations, the relationship between changes in carrier concentration and macroscopic EM parameter responses is quantified. Applying only plasma can effectively increase the donor defect level, thereby producing n-type unipolar carriers. As the doping concentration increases, the carrier polarity transitions from intrinsic n-type unipolarity to bipolarity or p-type unipolarity. The relaxation peak of the MoS₂ samples exhibits a positive shift at mid-frequency (7.8 GHz). This is attributed to plasma-assisted group IIIA element anchoring defects and Mo sites, which passivate surface defect states, thereby reducing charge traps and recombination, enhancing carrier concentration (from 0.65 × 10²³ m⁻³ to 5.75 × 10²³ m⁻³), and improving the dielectric response of doped TMDs. This significantly enhances the EMW absorption performance from MS (EAB, 0.82 GHz) to MS-15min-0.5In (EAB, 7.01 GHz). This work provides both a fundamental understanding of the electromagnetic response of TMDs under varying bipolarity carriers and a practical, dual plasma-assisted method for achieving controlled carrier polarity modulation.