Multi-junction lateral 2D heterostructures of transition metal dichalcogenides via sequential edge epitaxy<i> </i>

Here we demonstrate the successful synthesis of lateral in-plane multi-junction heterostructures based on transition metal dichalcogenides (TMD) 2D monolayers, using a modified chemical vapor deposition process where water vapor was use as a mediator for selective evaporation-deposition of the precursors. By only controlling the carrier gas composition, it is possible to selectively growth one TMD at the time. This introduces an unprecedented flexibility that allows a good in situ control of the lateral size of each TMD segment. The fabricated heterostructures include MoS₂-WS₂, MoSe₂-WSe₂ and MoS_xSe_y-WS_xSe_y, with multiple hetero-junctions. The band gap modulation across the junctions as well as spatial chemical distribution were studied by Raman and photoluminescence mapping. The crystalline quality of the heterostructures were characterized within an aberration-corrected scanning transmission electron microscope, revealing seamless interfaces with high-crystalline quality. Using field effect transistor devices we studied the transport properties across the junctions.