Tuning optical and electrical properties of mono and few layer two-dimensional transition metal dichalcogenides by strain

Research Project, 2021 – 2024

Monolayer two-dimensional (2D) transition metal dichalcogenides (TMDC) exhibit unique electrical, optical, mechanical and thermal properties compared to the bulk materials. Strain offers the possibility to tune the properties of the 2D TMDCs. While bulk semiconductors fracture at 0.5-1.5 % strain and corresponding nanowires fracture at about 3-5, the 2D structures can withstand up to 10% strain before fracture. 2D structures can also more easily be folded, stretched and bent compared to bulk structures. This enables more extensive and reversible tuning of the electrical and optical properties of 2D structures. The strain can, for example, induce a direct to an indirect band gap transition.The functionality of 2D TMDC structures is governed by atomic arrangement and strong confined electric fields. In this project, we will correlate site specific strain to local electrical and optical properties using advanced electron microscopy to reveal new information crucial for material design. Recent advances in forefront microscopy allow us to determine the positions of individual atoms with sub-picometer precision. Strain induced effects on energy band gap and optical resonances will be determined with subnano-meter spatial resolution. The local electric field distributions and optical resonances will be studied in operando conditions.