Strain Engineering of a Dual-Gate Structure for Highly Flexible and Transparent MoS₂ Thin-Film Transistors with Graphene Electrodes.

Abstract

Graphene and MoS₂ are two-dimensional materials with significant potential for future flexible electronic devices owing to their atomically thin structure, high mechanical flexibility, and high transparency. The high surface-to-volume ratio of MoS₂ enhances gate modulation in dual-gate structures compared to other channel materials. However, under bending conditions, mobility and ON-current increase due to tensile strain, whereas the threshold voltage (<i>V</i>_th) undergoes a negative shift and the <i>I</i>_ON/<i>I</i>_OFF current ratio significantly degrades. We propose a strategy that preserves the advantages of dual-gate structures, including a notable enhancement in the ON-current compared to single-gate devices, along with improved <i>I</i>_ON/<i>I</i>_OFF, subthreshold swing, and transconductance, even on flexible platforms. By designing a neutral plane, we reduced the tensile strain near the MoS₂ channel from 0.318 to 0.008% at a bending radius of 0.5 mm, as validated through COMSOL Multiphysics simulations. Our flexible MoS₂ thin-film transistors with graphene electrodes maintain excellent electrical performance even under harsh bending conditions with an <i>I</i>_ON/<i>I</i>_OFF of over 10⁸ and a <i>V</i>_th shift that remains within -0.3 V at a bending radius of 0.5 mm. These devices exhibit outstanding durability, withstanding over 16,000 bending cycles without notable degradation of transfer characteristics. Finally, the device has a high transmittance of 74.7% at 550 nm, making it well-suited for flexible and transparent electronic technologies.