Design rules for doped transition metal dichalcogenides heterostructures

Transition metal dichalcogenides (TMDs) are the base materials for diverse technological devices such as photovoltaics, lithium-ion batteries, hydrogen-evolution catalysis, transistors, photodetectors, DNA detection, memory devices, and nanotribological systems. Their flexible ${\mathrm{MX}}_{2}$ stoichiometry enables the fine-tuning of their properties via cation or anion substitution, thus allowing heterostructures with diverse functionalities to be engineered at the nanoscale. In this respect, we perform first-principles simulations to individuate possible novel structures derived from monolayer and bilayer ${\mathrm{MoS}}_{2}$ and ${\mathrm{WS}}_{2}$ alloyed with various metal and nonmetal dopants at different concentrations. We evaluate the relative stability and characterize the mechanisms responsible for their formation through electronic descriptors. Specifically, we identify bond covalency and orbital polarization as collective indicators for favorable electronic distributions, while the electronic structure of the isolated atom may be used for the selection of suitable dopants. The proposed methodology constitutes a general protocol, which can easily be extended to van der Waals heterostructures beyond those based on TMDs. Finally, the methodology can be used to help machine learning algorithms screen material databases for high-throughput discovery of new van der Waals--based alloys.