Lateral and Vertical Heterostructures of Transition Metal Dichalcogenides

In
this paper we investigate periodic lateral and vertical heterostructures
of transition metal dichalcogenides (TMDs). Lateral heterostructures
are constructed by the alternating metallic and semiconducting single-layer
stripes of TMDs joined commensurately along their armchair edges and
attain different states depending on the widths of constituents. While
these heterostructures acquire a composite character with metallic
state for narrow stripes, large stripes lead to the confinement of
electronic states and function as metal–semiconductor junctions
with a tunable Schottky barrier. The interface or boundary between
constituent stripes has finite extension and allows charge transfer
between them. On the other hand, the weak van der Waals interaction
between layers sets the features of vertical heterostructures. Their
interfaces are sharp: metal–semiconductor junction and Schottky
barrier developed thereof can be induced even within a few layers.
In the absence of dopants, we find minute charge transfer across the
interface with negligible band bending in vertical heterostructures.
The δ-doping of the semiconducting constituent by the metallic
one forms strictly two-dimensional metallic electrons in a three-dimensional
layered semiconductor and leads to crucial directionality effects
and quantization of conductance. Our work unveils significant differences
between lateral and vertical heterostructures.