Two dimensional WS2 lateral heterojunctions by strain modulation.

"Strain engineering" has been widely used to tailor the physical properties of layered materials, like graphene, black phosphorus, and transition-metal dichalcogenides. Here, we exploit thermal strain engineering to construct two dimensional (2D) WS₂ in-plane heterojunctions. Kelvin probe force microscopy is used to investigate the surface potentials and work functions of few-layer WS₂ flakes, which are grown on SiO₂/Si substrates by chemical vapor deposition, followed by a fast cooling process. In the interior regions of strained WS₂ flakes, work functions are found to be much larger than that of the unstrained regions. The difference in work functions, together with the variation of band gaps, endows the formation of heterojunctions in the boundaries between inner and outer domains of WS₂ flakes. This result reveals that the existence of strain offers a unique opportunity to modulate the electronic properties of 2D materials and construct 2D lateral heterojunction. [ABSTRACT FROM AUTHOR]