Enhanced Photoluminescence and Strain-driven Localization of Charge Carriers in Multilayer MoS₂ on Nanopillars

Funneling of charge carriers and excitons in TMDCs is an exciting venue to control optical quasiparticle locations and density. Application of non-uniform strain provides an energy gradient in the band structure that can achieve funneling. Here we report both exciton and electron funneling in locally strained multilayer MoS₂ on nanopillars of SiO₂/Si, with the MoS₂ film being suspended around the pillar. Spatially resolved Photoluminescence (PL) and Raman mapping show 1.5-2% biaxial strain on the pillar, with strain extending beyond the suspended region. We observe a strong charge increase in the pillar region via Raman A_1g red-shift, and a concomitant large increase in the trion contribution in the PL. The increase in radiative trion fraction and Raman A_1g shift is attributed to exciton to trion conversion by the strain-funneled electron supply. The indirect material also shows an overall 6-fold increase in the PL intensity due to strain, indicative of exciton funneling, confirmed independently from direct imaging with separate excitation and collection. Our results show that strain control could be used in addition to the electric field, as part of the toolbox for quasiparticle manipulation in 2D systems.