Strain-Induced Optimization of Nanoelectromechanical Energy Harvesting and Nanopiezotronic Response in a MoS2 Monolayer Nanosheet

Besides the intrinsic semiconducting direct band gap in monolayer MoS2 (ML-MoS2), piezoelectricity arises in it due to the broken inversion symmetry. This underscores the need to unveil the simultaneous response of piezoelectric and semiconducting properties to different modes of strain. The present study explores a synergic coupling between these two properties in adaptive nanopiezotronic devices, using density functional theory. Out of the different strain types studied, shear strain and uniaxial tensile strain applied along the zigzag direction are found to be most effectual in fortifying the piezoelectric properties in ML-MoS2. Shear strain is found to raise both the piezoelectric stress (e(11)) and strain (d(11)) coefficients by 3 orders of magnitude, while uniaxial tensile strain increases the same by 2 orders of magnitude for an applied mechanical strain of 5%. The effect is found to be even stronger upon reaching the elastic limit, which is found to lie within 510% strain for different strain modes studied. At around 45% of shear strain and about 67% of uniaxial tensile strain, nanopiezotronic properties are found to be optimally exploitable in ML-MoS2, when the piezoelectric coefficients are maximized while the semiconducting properties are retained. Additionally, carrier mobilities have been computed. The drastic drop in electron and hole mobilities at 3% uniaxial compressive strain and 1% uniaxial tensile strain respectively may be utilized in designing low-power switches. Compressive strain applied along the zigzag direction is found to boost both electron and hole mobilities. Our accurate predictive studies provide useful pointers for developing efficient nanopiezotronic devices, actuators, and nanoelectromechanical systems.