Tailoring Thermal Expansion Coefficient of Transition Metal Dichalcogenides via Alloy Engineering*

Transition metal dichalcogenides (TMDs) have shown intriguing properties which make them suitable as candidates for future electronics. For example, the thermal expansion coefficient (TEC) dramatically increases when the thickness is reduced to a monolayer. However, the TEC mismatch in 2-dim materials is a significant problem in the design of the electronic nano-device. Therefore, an effective method for controlling the TEC of TMDs and an understanding of the related mechanism are needed.

In this contribution, we will introduce alloy engineering to tune the TECs of monolayer Mo_1-xW_xS₂. We will study the relationship between the thermal expansion and the local defects using a combination of scanning transmission electron microscope (STEM), electron energy loss spectroscopy (EELS) and first-principles calculations. It is important to note that the TEC can be tuned through controlling the doping concentration. Atomic-resolution Z-contrast images and the corresponding nanometer-scale TEC maps will be used to explore the influence of local strain and defects on the thermal expansion.