Ricerc@Sapienza

In today's digital ecosystem, telecommunications have become the basis for businesses, governments, communities, and families to seamlessly connect and share information. Over time, telecommunications are expected to further expand. Therefore, there has been a great demand for light sources and photodetectors that work in the telecommunication band (1.3-1.5 µm) for signal transmission through silica optical fibers. Two-dimensional (2D) materials -i.e. single layers of a crystal, with atomic thickness- can nowadays be obtained from layered materials, thanks to the fact that the different layers are bound by the weak van der Waals force. Besides their atomic thickness, 2D materials are highly flexible and can withstand three to five times more strain (i.e., elastic deformation) than traditional three-dimensional semiconductors. As a two-dimensional material, MoTe2 has all these characteristics. MoTe2 has a band gap of 1.1 eV (i.e., ~1.13 µm) for a single layer and 0.98 eV (i.e., ~1.27 µm) for a bulk, making it a potentially suitable source material for the telecom band. However, the tuning of light emission is still the bottleneck for exploring the entire telecom span. As demonstrated by the host group, a process based on hydrogen irradiation on 2D multilayers (MoS2, WS2, WSe2, MoTe2) is able to induce the creation of strained nanometric or micrometric domes of monolayer thickness. The process can be exploited to achieve strains ~10%, which have not been demonstrated by other strain techniques used for 2D materials. The technique further allows us to gain control over the shape and size of the dome. While the effect of strain in domes formed in MoS2, WS2, and WSe2 has been widely studied by the host group, the effect on MoTe2 has not been characterized, yet. This project aims to explore the possibility to tune the luminescence properties of MoTe2 through strain in order to make it a controllable light source in the telecommunication wavelength range.