Phase engineering of seamless heterophase homojunctions with co-existing 3R and 2H phases in WS ₂ monolayers

flakes of different sizes. Time-resolved fluorescence lifetime imaging confirms distinct contrast between 2H and 3R phases with two distinct lifetimes of 3.2 ns and 1.1 ns, respectively. Kelvin probe force microscopy imaging revealed an abrupt change in the contact potential difference with a depletion width of ∼2.5 μm, capturing a difference in work function of ∼40 meV across the homojunction. Further, the thermal stability of coexisting phases and their temperature dependent optical behavior show a distinct difference among 2H and 3R phases. The investigated aspects of the controlled in plane growth of coexisting phases with seamless homojunctions, their properties, and their thermal stability will enable the development of nanoscale devices that are free from issues of lattice mismatch and grain boundaries.