High-Temperature Activation of Single-Photon Emitters in monolayer WS2

Controlled activation of defect-bound excitonic states in two-dimensional semiconductors provides a route to isolated quantum emitters and a sensitive probe of defect physics. Here we demonstrate that \textit{in situ} high-temperature annealing of hBN-encapsulated monolayer WS$_2$ on a suspended microheater leads to the emergence of spectrally isolated single-photon emitters at cryogenic temperatures. Annealing at temperatures around 1100 K produces a sharp emission line, $X_L$, red-shifted by approximately 80 meV from the neutral exciton and exhibiting a linewidth below 200 $\mu$eV. Photoluminescence excitation spectroscopy and power-dependent measurements show that $X_L$ originates from annealing-induced defects in the WS$_2$ monolayer, while second-order photon correlation measurements reveal clear antibunching with $g^{(2)}(0)<0.5$. These results establish high-temperature \textit{in situ} annealing as a controlled means to access defect-bound excitonic states and single-photon emission in van der Waals materials.