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Following isolation of a single sheet of graphene, many other 2D systems were manufactured. Among them, single transition metal dichalcogenides (TMD) sheets have received a particular attention, as these materials exhibit intriguing electronic, optical and mechanical properties which can be controlled by varying material composition. Moreover, the properties can further be tuned by introduction of defects and impurities. In this lecture, after a brief introduction to the structure and properties of TMDs, I will present the results of our first-principles theoretical studies of the morphology, electronic and optical properties of 2D TMDs obtained in collaboration with several experimental groups. I will further discuss how defects and impurities can be used to tune the characteristics of 2D TMDs. I will also touch upon the stability and electronic characteristics of mixed TMDs, such as MoS2xSe2(1−x), which can be referred to as 2D random alloys. We demonstrated that 2D mixed ternary MoS2/MoSe2/MoTe2 compounds are thermodynamically stable at room temperature, and that the gap in such systems is direct and can continuously be tuned, as confirmed now by the experiments carried out by several groups.

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Arkady V. Krasheninnikov, Aalto University, Finland
Seminar room 03, ETP
Contact: Thomas Michely