Speaker
Description
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. In this investigation we focus on the application of TMDs in tribology, which arises from their characteristic ultralow coefficient of friction (~ 10$^{-3}$) in high vacuum conditions. It is well known that TMD-based nano-devices experience nanotribological effects in dynamic environments leading to major challenges regarding their design, control and reliability. Such issues may be addressed by exploiting the flexible stoichiometry of TMDs via cation/anion substitution and multi-layer design. In this respect, we perform first principles simulations to individuate possible novel structures derived from monolayer and bilayer MoS$_2$ and WS$_2$ alloyed with various metal and non-metal dopants at different concentrations. We evaluate the relative stability and characterise the mechanisms responsible for their formation through electronic descriptors. Specifically, we identify bond covalency and orbital polarisation as collective indicators for favourable 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 protocal 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.
This work was co-funded by the European Union under the project “Robotics and advanced industrial production” (reg. no. CZ.02.01.01/00/22 008/0004590), by the Czech Science Foundation project No. 23-07785S, and by the Ministry of Education, Youth and Sports of the Czech Republic through the e-INFRA CZ grant number ID: 90254.
