Impact of prior reactions on the recovery behavior of MoS2 transistors

The electrical property changes in monolayer MoS₂ transistors were analyzed after bistriflimide (H-TFSI) treatment, which dissociates into hydrogen cations and TFSI anions in solution, followed by intensive acetone rinsing. Charge trapping effects were examined by varying the delay time (0.1, 1, 5 s) between voltage application and current measurement, revealing changes in electrical hysteresis. While degradation in device performance was primarily attributed to TFSI anion adsorbates, a transition to counterclockwise hysteresis was observed as H⁺ ion effects became more pronounced, leading to a reduction of degradation or slight improvement in performance. To further assess interface trap characteristics, low-frequency noise modeling was conducted for each device condition, enabling the extraction of trap density and Coulomb scattering effects. The reversibility of H-TFSI treatment effects was also evaluated through a 24-h acetone rinse. The results indicated that the impact of H⁺ ions was almost entirely reversed, restoring the interface trap density to its initial state. However, carrier mobility did not fully recover, suggesting that residual TFSI anion adsorbates remained on the surface, contributing to persistent degradation. These findings demonstrate that hydrogen cations can sufficiently penetrate and exit from both MoS₂ and SiO₂, allowing defect neutralization to be reset through aggressive rinsing. In contrast, TFSI anions, which adsorb onto the surface, are not fully removable using liquid-phase cleaning methods. This highlights a potential processing strategy in which a passivation layer, impermeable to large molecules, is placed on top of the device before H-TFSI treatment, enabling selective defect passivation solely by H⁺ ions.