The Role of Defects and Mechanical Deformations in Transition Metal dichalcogenides

In recent years, Van der Waals (2D) materials, have attracted increasing attention due to their distinctive physical properties. As layered materials, they have been considered for flexible electronics as they can sustain strain higher than 10% without breaking down, although they are only 1-3 atom thick. In addition, 2D materials usually possess a large density of defects that can govern many of their physical properties. In this talk I will present a specific material from the 2D materials family, transition metal dichalcogenides (TMDC) and the role of defects in these materials. I will show how we can apply non-uniform strain to a suspended Van der Waals material (WS₂) and alter the dynamics of excitons and trions. Surprisingly, we find that as we increase the non-uniformity of the strain, we are able to convert the excitons into trions with almost 100% efficiency without any electrostatic gating, due to the presence of defects in TMDC. We also investigate the role of defects in gas sensing and reveal the real mechanism behind gas sensing in TMDC. Our results explain inconsistencies in previous experiments and pave the way towards new types of optoelectronic devices.