Study of strain engineered MoS2 and its application in lactic acid biosensors

Abstract

Two-dimensional (2D) materials exhibit promising applications in flexible electronics and biosensing due to their unique electrical and mechanical properties. Among them, molybdenum disulfide (MoS₂), as a typical 2D semiconductor, demonstrates piezoelectric properties in its monolayer state due to the absence of an inversion symmetry center. This study investigates the piezoelectric behaviors of monolayer MoS₂ under strain. Studies of metal–semiconductor (MS) and PN junction devices reveal that MoS₂ conductivity is modulated by an internal electric field generated by piezoelectric polarization. This electric field regulates the height of the Schottky barrier at electrode contacts, while compressive strain elevates it and tensile strain lowers it. The results of this study on MS devices fabricated on flexible polyethylene terephthalate (PET) substrates further reveal piezoelectric-dominated asymmetric current modulation. This phenomenon is considered to have the potential to improve the sensing performance for lactic acid detection. Consequently, we conducted lactate sensing under tensile conditions, leading to an approximately five times increase in the sensitivity of flexible MS devices toward lactate (0–1 µM) under 0.29% tensile strain conditions. This study provides a feasible approach for exploring highly sensitive wearable biosensors.