Coplanar semiconductor–metal circuitry defined on few-layer MoTe2 via polymorphic heteroepitaxy

Crystal polymorphism selectively stabilizes the electronic phase of atomically thin transition-metal dichalcogenides (TMDCs) as metallic or semiconducting, suggesting the potential to integrate these polymorphs as circuit components in two-dimensional electronic circuitry. Developing a selective and sequential growth strategy for such two-dimensional polymorphs in the vapour phase is a critical step in this endeavour. Here, we report on the polymorphic integration of distinct metallic (1T′) and semiconducting (2H) MoTe 2 crystals within the same atomic planes by heteroepitaxy. The realized polymorphic coplanar contact is atomically coherent, and its barrier potential is spatially tight-confined over a length of only a few nanometres, with a lowest contact barrier height of ∼25 meV. We also demonstrate the generality of our synthetic integration approach for other TMDC polymorph films with large areas. Sequential heteroepitaxy of transition-metal dichalcogenide polymorphs with different electronic properties is used to build coplanar ultrathin circuitry with atomic-scale precision.