Tip-induced nano-engineering of strain, bandgap, and exciton dynamics in low-dimensional semiconductors

Abstract

We demonstrate a dynamic nano-mechanical strain-engineering of naturally-formed wrinkles in a WSe2 monolayer, with real-time investigation of nano-spectroscopic properties using hyperspectral adaptive tip-enhanced PL (a-TEPL) spectroscopy. First, we characterize nanoscale wrinkles through hyperspectral a-TEPL nano-imaging with <15 nm spatial resolution which reveals the modified nano-excitonic properties by the induced tensile strain at the wrinkle apex, e.g., an increase in the quantum yield due to the exciton funneling, decrease in PL energy up to ~10 meV, and a symmetry change in the TEPL spectra caused by the reconfigured electronic bandstructure. We then dynamically engineer the local strain by pressing and releasing the wrinkle apex through an atomic force tip control. This nano-mechanical strain-engineering allows us to tune the exciton dynamics and emission properties at the nanoscale in a reversible fashion.