Monolayers of W_xMo_1−xS₂ alloy heterostructure with in-plane composition variations

We report the fabrication of single-crystal monolayer W_xMo_1−xS₂ alloy triangles using chemical vapor deposition method. Raman and photoluminescence property are investigated in correlation to the composition. In the monolayer triangles, the photoluminescence peak shifts continuously from 687.4 nm at the triangle center to 633.6 nm at the edge, corresponding to a switch from MoS₂ to WS₂ across the heterojunction. This composition-graded alloy may have interesting functions in broadband photodetection and multi-color light emission.