All‐optical dynamic tuning of local excitonic emission of monolayer MoS ₂ by integration with Ge ₂ Sb ₂ Te ₅

Strong quantum confinement and coulomb interactions induce tightly bound quasiparticles such as excitons and trions in an atomically thin layer of transitional metal dichalcogenides (TMDs), which play a dominant role in determining their intriguing optoelectronic properties. Thus, controlling the excitonic properties is essential for the applications of TMD‐based devices. Here, we demonstrate the all‐optical tuning of the local excitonic emission from a monolayer MoS 2 hybridized with phase‐change material Ge 2 Sb 2 Te 5 (GST) thin film. By applying pulsed laser with different power on the MoS 2 /GST heterostructure, the peak energies of the excitonic emission of MoS 2 can be tuned up to 40 meV, and the exciton/trion intensity ratio can be tuned by at least one order of magnitude. Raman spectra and transient pump‐probe measurements show that the tunability originated from the laser‐induced phase change of the GST thin film with charge transferring from GST to the monolayer MoS 2 . The dynamic tuning of the excitonic emission was all done with localized laser pulses and could be scaled readily, which pave a new way of controlling the excitonic emission in TMDs. Our findings could be potentially used as all‐optical modulators or switches in future optical networks.