Gate-Tunable MoS2/h-BN Transistors With Ion Gel Dielectric: Subthreshold Swing 62 mV/dec, Room-Temperature Electron Mobility 124 cm2/Vs, and Flexible Substrate Integration

This study investigates gate-tunable MoS2/h-BN field-effect transistors with ion gel top gate achieving near-ideal subthreshold swing, high electron mobility, and successful transfer to flexible PET substrates within the context of 2D materials science and flexible electronics, an area of growing scientific importance given its implications for flexible wearable biosensor transistors, 2D material-based low-power logic, and van der Waals heterostructure FET design guidelines. Using mechanical exfoliation and van der Waals heterostructure assembly (MoS2/h-BN/graphite gate) in N2 glovebox, Pd/Au electrode deposition by e-beam evaporation, ion gel spin-coating, 4-probe resistivity and Hall effect at 77-300 K, and transfer to PET flexible substrate by PDMS stamp, we examine h-BN substrate eliminating charged impurity scattering that limits SiO2-gated MoS2 mobility; ion gel high capacitance (>10 uF/cm2) enabling ultra-low operating voltage (<1 V) and Debye-Hutter screening of Coulomb disorder; residual phonon scattering dominating at room temperature limits mobility ceiling in 24 MoS2 FET devices (12 monolayer, 12 bilayer) on h-BN with ion gel gate; 8 devices transferred to flexible PET; measurements at 300 K and 77 K with 5 gate sweep cycles per device drawn from Ridgemont Materials Science Institute cleanroom with N2-atmosphere glovebox (Jacomex, <0.1 ppm O2/H2O), Nanoscope AFM for layer counting, and Keithley 4200 semiconductor analyzer. Results indicate that Hall mobility 124 cm2/Vs at 300 K (84 cm2/Vs flexible PET); subthreshold swing 62 mV/dec (vs. thermal limit 60 mV/dec); on/off ratio >10^8; <5% Vth shift after 1000 bending cycles at 5 mm radius (p < 0.001), with mobility 124 cm2/Vs; SS 62 mV/dec; on/off >10^8; <5% Vth shift after bending as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to 2D materials science and flexible electronics and carry actionable implications for the design of programs and policies targeting flexible wearable biosensor transistors, 2D material-based low-power logic, and van der Waals heterostructure FET design guidelines.