WS2–graphene heterostructures with hydrogen-controlled morphology: Interfacial charge transfer and negative photoresponse

We report a hydrogen-assisted chemical vapor deposition (CVD) strategy for the controlled synthesis of triangular-shaped WS 2 flakes and demonstrate their integration with graphene to construct optoelectronic heterostructures. By systematically tuning the H 2 flow rate during WS 2 growth, we modulate flake density and layer thickness. Raman and XPS analyses reveal highly crystalline bilayer WS 2 with minimal contamination. Upon transferring graphene onto WS 2 flakes, we observe distinct doping-induced Raman shifts and p -type behavior in field-effect transport. Notably, the WS 2 –graphene heterostructure exhibits photocurrent quenching under UV irradiation, attributed to efficient interfacial charge transfer. This study elucidates the role of H 2 in nucleation control and highlights the potential of WS 2 –graphene heterostructures for photodetection applications. • Hydrogen-assisted CVD was used to control the morphology and density of WS 2 flakes. • The WS 2 –graphene heterostructure exhibited p-type doping in graphene, confirmed by Raman spectroscopy. • The WS 2 –graphene photodetector demonstrated a unique negative photocurrent response under UV light. • The photoresponse of the devices showed dependence on the density of WS 2 flakes.