Lateral Chemical Bonding in Two-Dimensional Transition-Metal Dichalcogenide Metal/Semiconductor Heterostructures

Discovering
better materials for electronic
devices is important for technological advancements. One of the most
promising materials are transition-metal dichalcogenides (TMDCs) due
to their ability to form two-dimensional structures with diverse compositions.
Recently, experimental breakthroughs were demonstrated for all two-dimensional
transistors that contain a semiconducting TMDC channel and other materials
for the metallic source and drain. However, metal/semiconductor interfaces
that are made of similar TMDC materials are anticipated to be better
candidates because they provide better chemical bonding and thus smaller
resistance. Furthermore, smaller resistance is expected to be achieved
with a metal and a semiconductor that are joined in direct lateral
contact. In this work, we use density functional theory to analyze
the electronic structure properties of novel lateral TMDC metal/semiconductor
heterojunctions. We discover promising metal/semiconductor heterojunctions,
for example, VS2/CrS2, which is characterized
by strong covalent bonds with limited metal-induced gap states, high
charge density around the Fermi level, and no Schottky barrier. These
properties are anticipated to be useful for practical implementation
of these material heterojunctions in all two-dimensional transistors.