Fig. 1. (Color online) Schematic of a modified bidirectional flow CVD system.

Fig. 2. (Color online) (a) Optical image of monolayer WS₂. (b) PL spectrum of WS₂. (c) Raman spectrum of WS₂. (d) Optical image of WS₂ in the yellow rectangle of (a). (e) PL mapping image of monolayer WS₂. (f) Raman mapping image of monolayer WS₂.

Fig. 3. (Color online) AFM images of WS₂/WSe₂ lateral heterostructure when the growth time are (a) 5 s, (b) 7 s, (c) 9 s, (d) 11 s, (e) 30 s and (f) 40 s.

Fig. 4. SEM image of the 2D/1D WS₂/WSe₂ lateral heterostructure.

Fig. 5. (Color online) AFM phase image of WS₂/MoS₂ lateral heterostructure when the growth time are (a) 3 min, (b) 1 min, and (c) 30 s.

Fig. 6. (Color online) Raman and PL spectrum of WS₂/MoS₂ and WS₂/WSe₂ heterostructures. (a) Raman spectrum of the WS₂/MoS₂ heterostructure. (b) PL spectrum of the WS₂/MoS₂ heterostructure. (c) Raman spectrum of the WS₂/WSe₂ heterostructure. (d) PL spectrum of the WS₂/WSe₂ heterostructure.