Epitaxial growth of a monolayer WSe ₂ -MoS ₂ lateral p-n junction with an atomically sharp interface

TLDR

Two‑dimensional materials such as graphene and transition‑metal dichalcogenides (TMDCs) offer nanoscale transistors with high on/off ratios, but graphene’s lack of a band gap makes it leaky, and forming voltage‑biased p‑n junctions between different TMDCs remains challenging. The authors grew MoS₂ on the edge of a WSe₂ triangle, creating an atomically sharp lateral p‑n junction rather than stacking the layers, thereby achieving a stronger interface. They successfully fabricated a monolayer WSe₂.

Abstract

Electronic junctions on edge Two-dimensional materials such as graphene are attractive materials for making smaller transistors because they are inherently nanoscale and can carry high currents. However, graphene has no band gap and the transistors are “leaky”; that is, they are hard to turn off. Related transition metal dichalcogenides (TMDCs) such as molybdenum sulfide have band gaps. Transistors based on these materials can have high ratios of “on” to “off” currents. However, it is often difficult to make a good voltage-biased (p-n) junction between different TMDC materials. Li et al. succeeded in making p-n heterojunctions between two of these materials, molybdenum sulfide and tungsten selenide. They did this not by stacking the layers, which make a weak junction, but by growing molybdenum sulfide on the edge of a triangle of tungsten selenide with an atomically sharp boundary Science , this issue p. 524